Show all abstracts
View Session
- Front Matter: Volume 7753
- A Look Back at Optical Fiber Sensors
- Current Fiber Sensor Applications and Technologies
- Plenary Talk
- Brillouin Sensors
- Micro- and Nano-Fibers
- Sensor Applications
- Poster Session: Mach-Zehnder, SPR, Fabry-Perot, Interferometer, Resonator, Brillouin, Distributed, Laser
- Rayleigh Techniques and Frequency Domain Sensors
- New Fibers
- Poster Session: Microstructural Fiber, Novel Concepts, etc.
- PCF Sensors
- FBG Sensors
- Multimode Effects
- Biomedical Applications
- Poster Session: Bragg Gratings, Long Period Gratings, Specialized Gratings
- Sensor Characterization
- Post Deadline Paper Session
Front Matter: Volume 7753
Front Matter: Volume 7753
Show abstract
This PDF file contains the front matter associated with SPIE Proceedings Volume 7753, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.
A Look Back at Optical Fiber Sensors
Optical fiber sensor research and industry in Germany: review and outlook
Show abstract
Since more than 30 years, the increased research, technology development and commercialization of optical fiber sensors
combined with their continuously growing technical applications have become a story of success worldwide and in
Germany as well. German fiber sensor research and industry achieved remarkable milestones in the 1980ies and 1990ies,
such as first field tests of magneto-optic current sensors in power facilities or of micro-bending fiber strain sensors in a
highway bridge. Recent progress and the state of the art of optical fiber sensing in Germany are demonstrated by
examples of advanced fiber Bragg grating and distributed sensor system applications, fiber gyroscopes and other
interferometric sensors, chemical and bio-medical sensors, and sensors based on polymer fibers as well.
In context with the growing international cooperation, the potential of German research and industry will be discussed in
terms of novel fiber-optic sensor system concepts, of increasing maturity and reliability of this exciting sensor
technology and of new applications and markets.
The origin, history and future of fiber-optic interferometric acoustic sensors for US Navy applications
Show abstract
Fiber-optic interferometric acoustic sensors were first proposed for US Navy applications 36 years ago. This paper will review the origin, development and deployment of these sensors. Future applications will also be discussed.
Current Fiber Sensor Applications and Technologies
Pressure measurement with fiber-optic sensors: commercial technologies and applications
Show abstract
Mainly three technologies are presently commercially available for pressure measurement with
fiber-optic sensors: intensity-based, fiber Bragg gratings and Fabry-Pérot. The first one is probably the
simplest and the cheapest but it is limited to applications where having 2 fixed or up to 4 flexible fibers is not
an issue, whereas the two other technologies require only one fiber. With generally low sensitivity to pressure
and prohibitive cost for non multiplexed measurements, fiber Bragg grating pressure sensors are still limited
to marginal applications. Fabry-Pérot technology is the best compromise offering at affordable price a great
flexibility in terms of pressure ranges, high sensitivity and miniature size suitable for most applications
including disposable medical devices.
Distributed sensing with OFDR and its application to structural health monitoring
Show abstract
Optical fiber sensors are promised candidates as sensor elements in structural health monitoring (SHM). Especially
fiber-optic distributed strain sensors that return a strain value as a function of linear position along an optical fiber have
been attractive for people in the field of SHM. We have developed a distributed strain sensing system using long-length
fiber Bragg gratings (FBGs), based on optical frequency domain reflectometry (OFDR). We employ long-length FBGs
whose length is about 100 mm and the sensing region, in other words the gauge length, can be expanded up to more than
1 m by serially-cascaded long-length FBGs. This sensing system has the high spatial resolution of less than 1 mm. In this
paper the distributed sensing system with OFDR and its application to SHM are described.
Plenary Talk
Sensing high speed phenomena using fiber gratings and the Sagnac interferometer
Show abstract
Fiber grating sensors and the Sagnac interferometer can be used to support a wide variety of high speed
measurement applications. This paper explores the uses of both of these types of fiber optic sensors to
measure environmental phenomenon at high speeds. In both cases there are environmental measurements
that can be made at speeds that are limited only by the speed of the output detectors. In others the
limitation is the response of the optical fiber itself. A series of examples will be given that illustrate the
historical usage and future utility of these sensors to operate at speeds and in environments that would be
very difficult for electrical sensors to match.
Brillouin Sensors
Brillouin scattering accompanied by acoustic grating in an optical fiber and applications in fiber distributed sensing
Kazuo Hotate
Show abstract
Fiber optic distributed sensing systems based on Brillouin scattering are reviewed. Strain or temperature distribution
along an optical fiber can be measured with this phenomenon using time domain and correlation domain techniques.
Superior functions have already been demonstrated, such as mm order spatial resolution and kHz order measurement
speed. Brillouin scattering is accompanied by acoustic grating, which is generated by thermal vibration of fiber material.
Recently, considering the nature of the acoustic grating enhanced through stimulated Brillouin scattering process, various
advanced functions have been realized in the distributed sensing, such as discriminative measurement of strain and
temperature with a 10 cm resolution by a correlation domain technique, realization of cm order resolution by a time
domain technique, and distributed birefringence measurement along a polarization maintaining fiber. These Brillouin
based systems are also compared briefly with FBG based systems, including distributed sensing with long-length FBG.
100km sensing range Brillouin optical time domain analysis based on time-division multiplexing
Show abstract
We propose and demonstrate a novel high-performance 100-km range Brillouin optical time-domain analysis (BOTDA)
based on time-division multiplexing. To avoid the limitation of pump depletion or excess amplification in a conventional
long-range BOTDA, in our scheme instead of a pulse and a CW wave but two pulses, i. e., a probe pulse and a pump
pulse are used to perform the measurement. The delay between the probe and pump pulses can be changed to select the
sensing section where the probe pulse interacts with the pump pulse. The measurement of the entire sensing fiber is
realized by implementing the measurement for each sensing section through changing the delay between the two pulses.
In experiment, a 100-km sensing fiber is divided into 11 sections based on gain-controlled principle, and a spatial
resolution of 0.6 m and 2 m are obtained at the end of 75 km and 100 km, respectively.
Hot spot detection over 100 km with 2 meter resolution in a Raman-assisted Brillouin distributed sensor
Show abstract
We have developed a long-range Brillouin distributed sensor featuring 100 km measuring distance with 2 meter
resolution. To our knowledge, this is the first time that a high-resolution setup reaches the barrier of 100 km
measurement range. The key improvements with respect to previous configurations are explained.
Measurement range elongation based on a temporal gating scheme in Brillouin correlation domain distributed discrimination system for strain and temperature operated by a single laser
Show abstract
We have demonstrated distributed discrimination of strain and temperature by localizing and scanning both the
Stimulated Brillouin scattering (SBS) and the Brillouin dynamic grating (BDG) along a polarization maintaining fiber,
with elongated measurement range. The localization and scanning is performed by a correlation domain technique,
whose measurement range is restricted by the distance between consecutive correlation peaks. To overcome this
restriction, we applied a temporal gating scheme to the system, enlarging the measurement range from ~8 m to ~500 m.
Here, we report the results confirming the effectiveness of this scheme in a system operated by a single laser source and
demonstrate strain-temperature discrimination when strain or temperature is applied to segments on the 500-m-long fiber
under test.
Faraday rotating Brillouin sensor system
Show abstract
A Faraday Rotating Brillouin Sensor System (FRoBS) is described and experimentally verified to reduce abrubt
temperature/strain change distortions of the Brillouin Spectrum.This single-ended Brillouin System is created
by modifying a typical Brillouin Optical Time-Domain Analysis system and adding a Faraday Rotating Mirror
(FRM) and a Polarization Beam Splitter (PBS).Both lasers are combined with a PBS and are launched into
the sensing fibre together.The remote end of the sensing fibre has a FRM attached that enables Brillouin
measurement of the outgoing waves as well as the incoming waves, resulting in a mirrored time-domain waveform.
Using weighted averages of the mirrored waveform results in a reduction in the aforementioned distortion.
Micro- and Nano-Fibers
Optical fibre microwire sensors
Show abstract
This paper reviews sensing applications of optical fibre microwires and nanowires. In addition to the usual benefits of
sensors based on optical fibres, these sensors are extremely compact and have fast response speeds. In this review
sensors will be grouped in three categories according to their morphology: linear sensors, resonant sensors and tip
sensors. While linear and resonant sensors mainly exploit the fraction of power propagating outside the microwire
physical boundary, tip sensors take advantage of the extreme light confinement to sense chemicals within minute areas.
Self-assembly and nanotechnology within an optical fibre for improved evanescent field sensing
Show abstract
The self-assembly of TiO2 nanoparticles is used to create a high index layer within a
structured optical fibre. We show both experimentally (using a novel porphyrin probe) and theoretically
that this approach leads to more than order of magnitude enhanced localisation of the optical field at
the layer-air interface of the hole, both through edge localisation and through novel resonance
localisation as a result of a ring resonator whispering gallery modes.
Tunable Fabry-Perot filter based on hollow-core photonic bandgap fiber and micro-fiber and its application
Show abstract
A novel tunable Fabry-Perot (F-P) filter is reported in this paper. The interference cavity is the hollow core of hollowcore
photonic bandgap fiber (HC-PBF), which supports fewer modes than the conventional cavities. One of the reflection
mirrors is the splicing point between a section of HC-PBF and a single mode fiber. The other one is a cleaved end of a
section of micro-fiber, which is inserted into the hollow core of HC-PBF. The cavity length of the F-P device can be
tuned by adjusting the position of the micro-fiber in the hollow core. Because of the low loss of HC-PBF, the F-P cavity
length can reach several millimeters, even up to the order of centimeters, which results in its very narrow linewidth and
high multiplexing capability. The experimental results show that the F-P filter has a fringe contrast of over 4 dB over a
wide wavelength range, which can be used as the tunable filter in a fiber laser to obtain a very narrow linewidth.
An optical trapping based microfiber vibration sensor
Show abstract
A novel microfiber vibration sensor based on optical trapping mechanism is proposed. In the vibration sensor, a
polystyrene microsphere with a diameter of 10μm is used as the mass block. The polystyrene microsphere is enclosed in
a sensing cavity filled with refractive index matching liquid. The sensing cavity is composed of a quartz capillary with an
inner diameter of 40μm whose two ends are inserted with two optical fibers with an outer diameter of about 40μm. The
end surface of the each fiber is fabricated to be a concave tip to generate scattering and gradient forces for trapping the
mass block. By adjusting light power outgoing from the two concave tips, the mass block can be suspended at center of
the sensing cavity. When a vibration is applied on the sensing cavity, the location of the microsphere will change with
the vibration, which results the light power from one tip collected by the other tip also varies with the vibration. The
response of the vibration sensor is experimentally demonstrated at frequency range from 15Hz to 1000Hz. The vibration
sensor has advantages of simple configuration, small size, light weight as well as good vibration response.
Etched core fiber Bragg grating sensor integrated with microfluidic channel
Show abstract
We demonstrate an etched-core fiber Bragg grating sensor for detection of bio-chemical agents. The fiber Bragg grating
of the sensor is etched to a diameter of 7 μm. The transition between the etched and the unetched core consists of an
asymmetric taper resulting in excitation of multiple modes. The different excited modes respond differently to change in
refractive index, temperature and strain. This allows for measurements for changes in these three parameters in a single
measurement by simultaneous measurement of reflections in Bragg wavelengths for different modes. This parametric
discrimination is confirmed experimentally by measuring the refractive index of water as temperature is increased. The
sensor is then integrated in a micro-fluidic channel fabricated using Polydimethylsiloxane (PDMS) substrate and tested
by introducing different chemicals. The sensitivity of the sensor to refractive index change is 92 nm/riu close to the
refractive index of water. Assuming a wavelength resolution of 1 pm, index resolution of 1x10-5, a strain resolution of 1
microstrain, and a temperature resolution of 0.032 ºC is achieved by the sensor.
Sensor Applications
Demodulation technique for plasmonic fiber grating sensors using orthogonally polarized light states
Show abstract
The generation of surface plasmon resonances (SPRs) in gold-coated weakly tilted fiber Bragg gratings (TFBGs)
strongly depends on the state of polarization of the core guided-light. Recently, it was demonstrated that rotating the
linear state of polarization of the guided light by 90° with respect to the grating planes allows to turn the SPR on and off.
In this paper, we demonstrate that this strong polarization dependence can be advantageously used to demodulate the
TFBG amplitude spectrum and retrieve the SPR shift induced by a change of the surrounding refractive index. The
correlation between two amplitude spectra recorded with two particular orthogonally polarized light states yields a new
refractive index measurement method accurate to ~2 10-5.
In situ radiation influence on strain measurement performance of Brillouin sensors
Show abstract
A new approach is proposed to monitor in situ the influence of gamma radiations on Brillouin properties of optical fiber
extensometers. Experimental results are illustrated with the characterization of two fibers samples up to total dose of
about 600Gy. The Brillouin frequency shift remains unaffected at such radiations level, as well as the spectral Brillouin
signature or its dependence with strain. Meanwhile, propagation losses increase under radiations with an amplitude
related to fiber dopants. The target application is nuclear wastes repository monitoring where higher doses are expected.
UV radiation preliminary tests show that compaction phenomenon may occur at such high doses, inducing Brillouin
frequency shift up to 20 MHz.
Self-packaged Type II femtosecond IR laser induced fiber Bragg grating for temperature applications up to 1000 °C
Show abstract
We propose a thermally stable Type II grating made with ultrafast infrared radiation in a silica-based 400 μm clad single
mode fiber cane as a self packaged grating due to its ability to maintain good mechanical integrity after more 100 hours
at 1000°C.
Evaluation of the transversal strain state in a satin weave composite using fibre Bragg gratings
Show abstract
Satin woven composites can be seen as a series of connected unit cells with a definite length and width. Along the length
and width of one unit cell, local strain fields can vary significantly due to the yarn interlacing pattern. Embedded Type I
FBGs with a 80 μm- and 125 μm cladding diameter are used to study the internal transversal strain variations in unloaded
and tensile loaded thermo-plastic 5-harness satin weave composite test specimens. The residual strains are
examined at different (axial) load levels up to 300MPa and 1.2million cycles. Differential transversal strains up to 0.07%
are presented. Results show that the embedded FBGs are capable of measuring long term the transversal strain
distributions. It is found that the yarn interlacing pattern of the satin weave composite causes complex and random local
strain fields during loading and that, even though axial strain measurements are matching very well with external strain
measurements, a large scatter exists in local transversal strain states between the different composite test-coupons.
Poster Session: Mach-Zehnder, SPR, Fabry-Perot, Interferometer, Resonator, Brillouin, Distributed, Laser
A novel positioning method for dual Mach-Zehnder interferometric vibration sensor in submarine cable security application
Show abstract
Dual Mach-Zehnder interferometric vibration sensor is an appropriate solution for submarine cable security application. While in this application the detected vibration signal is always narrow-bandwidth and short-duration subject to environmental constraints, which makes correlation based vibration positioning algorithm a poor robustness to noise. A preprocessing method focusing on expanding signal 3dB bandwidth before correlation is proposed in purpose of reducing ultimate positioning mean square error. A high pass filter is imposed to enhance the weight of high frequency components by attenuating low frequency main lobe. Field test results indicate a significant positioning error reduction when using this novel method as long as the cutoff frequency of high pass filter is selected in a valid region where positive effect of bandwidth extension is larger than effect of SNR reduction, and MSE reduction value in valid region agrees well with theoretical prediction.
Fiber in-line Mach-Zehnder interferometer based on selective infiltration of photonic crystal fiber
Minwei Yang,
D. N. Wang,
Ying Wang,
et al.
Show abstract
By use of femtosecond laser assisted micro-machining, a novel kind of fiber in-line Mach-Zehnder interferometer is
fabricated through selective infiltrating of the solid core photonic crystal fiber. Two adjacent air holes of the innermost
layer are infiltrated of liquid with refractive index higher than that of the background silica. Theoretical analysis shows
that fundamental and higher order rod modes can be excited and interference can occur between the rod modes and the
fiber core mode. The temperature sensitivity of the device is measured to be -10.9 nm/ºC, which corresponds to a
refractive index sensitivity of 2.7x104 nm/RIU.
In-line all-fiber Fabry-Perot and Mach-Zehnder interferometers formed by hollow fiber with lateral offset
Show abstract
Two kinds of novel in-line all-fiber interferometers, including tip Farby-Perot interferometer and compact Mach-Zehnder
interferometer, are proposed and demonstrated by automatically fusion splicing a short section of hollow fiber to the end
of a single-mode fiber (SMF) and sandwiching a section of hollow fiber in two section of SMF with a tiny intentional
lateral offset that induces the optical path difference (OPD) required to form the two interferometers, respectively.
Temperature responses of both the two interferometers are studied experimentally. It is anticipated that such an easy
making, compact and low cost fiber-optic interferometers could find important applications in practice.
Experimental demonstration on 2.5m spatial resolution and 1oC temperature uncertainty over 74.6km BOTDA with combined Raman amplification and optical pulse coding
Show abstract
The combination of Raman amplification and optical pulse coding (OPC) is proposed to reduce the frequency
uncertainty in long-distance BOTDA under higher spatial resolution. The experimental characterization of 74.6Km
temperature sensing with measurement accuracy ~1oC under ~2.5m spatial resolution over the whole length of
sensing fiber is demonstrated. The performance comparisons of BOTDA with purely Raman amplification and
combined Raman amplification with OPC are also displayed.
A novel quasi-distributed sensing network based on non-balance Mach-Zehnder autocorrelator
Show abstract
We develop and demonstrate a non-balance Mach-Zehnder autocorrelator based quasi-distributed sensing network. A
three-port optical fiber circulator is used to connect broadband light source, sensor array and autocorrelator, avoiding
reflective light from sensor array reentering into the light source. At detection location, a balanced detection approach is
employed for restraining beat noise of the low coherent interferometric sensing network by respectively connecting two
photodetectors to the two output ports of the Mach-Zehnder autocorrelator. The characteristics of the unidirectional
transmission and differential output detection can at least double the effective efficiency of the light source power. The
optimization and signal-to-noise of the sensing system are theoretically discussed, and a thirteen-sensor network is
experimentally demonstrated. The full-fiber and common-path sensing system with high signal-to-noise is quite suitable
for quasi-distributed measurement of strain and temperature in smart structures.
Refractive index and temperature sensor based on double-pass in-line Mach-Zehnder interferometer
Show abstract
Different from the conventional optical fiber in-line Mach-Zehnder interferometer (MZI), we proposed and demonstrated
a novel double-pass in-line fiber taper MZI as a refractive index and temperature sensor in this study. The double-pass
MZI is composed of a reflecting mirror, a circulator and an in-line fiber MZI. The attenuation peaks of the double-pass
MZI spectra have higher contrasts than the peaks of single-pass spectra. Using our recently proposed spectrum
differential integration (SDI) analyzing method, the double-pass MZI sensors' sensitivities can be made nearly twice as
large as those of the single-pass ones.
Fiber loop ringdown strain sensor with photonic crystal fiber based Mach-Zehnder interferometer
Show abstract
A highly sensitive strain sensor is demonstrated by inserting a photonic crystal fiber (PCF) based Mach-Zehnder
interferometer (MZI) in a cavity ringdown fiber loop as the lossy sensing element. The MZI consists of a piece of PCF
spliced to single-mode fibers, in which the PCF air holes are collapsed over a short region at two splicing points for
coupling the core and cladding modes. By measuring the decay constants of the fiber ringdown loop, a high strain
sensitivity of ~0.21 μs-1/mε and a minimum detectable strain of ~3.6 με were obtained.
Curvature measurement with photonic crystal fiber based Mach-Zehnder interferometer
Show abstract
A PCF-based MZI with regular and high-contrast fringe pattern is fabricated by splicing a section of PCF in between two
SMFs with a commercial available fusion splicer. Its resonant wavelength is sensitive to external bending with a
sensitivity of 3.046nm/m but independent on temperature. To that end, we also propose another kind of bending sensor
with higher sensitivity of 5.129nm/m. This device is constructed by combining an LPG and an MZI with zero offset at
the second splice. It is anticipated that the high sensitive structures will find applications in robot arms and artificial
limbs.
PCF-based Fabry-Perot interferometric sensor for strain measurement under high-temperature
Show abstract
We report a simple and robust all-fiber in-line Fabry-Perot interferometer (FPI) with bubble cavity, which is fabricated by
directly splicing a mutimode photonic crystal fiber to a conventional single mode fiber by using a commercial splicer.
The fabrication process only involves fusion splicing and cleaving. The high-temperature strain characteristic of such a
device is evaluated and experimental results shows that this FPI can be used as an ideal sensor for precise strain
measurement under high temperatures of up to 750°C. Therefore, such a FPI sensor may find important applications in
aeronautics or metallurgy areas.
Microstructured fiber Mach-Zehnder interferometers for simultaneous measurement of axial strain and temperature
Show abstract
Three different types of microstructured asymmetrical fiber Mach-Zehnder interferometers (aFMZIs) consisting of a
fiber taper, a lateral-shifted junction, or a femtosecond laser irradiated spot are demonstrated to realize simultaneous
measurement of axial strain and temperature. These aFMZIs of different device architectures exhibit different
environmental sensitivities. For the taper/junction type aFMZI, the experimental results indicate temperature sensitivities
of 60.6 and 64.0 pm/°C (redshifts) and strain sensitivities of -1.48 and -2.72 pm/με (blueshifts) at higher and lower
interference orders m1 (49) and m2 (48), respectively. The other taper/spot and junction/spot type aFMZIs show similar
performance and demonstrate the effectiveness of the approach.
Polarization-dependent in-line Mach-Zehnder interferometer for discrimination of temperature and ambient index
Show abstract
Polarization-dependent in-line Mach-Zehnder interferometer fabricated by using a polarization-maintaining fiber
depending on input polarization state is investigated for discrimination of temperature and ambient index.
Miniaturized fiber-optic surface-plasmon-resonance sensor
Tobias Schuster,
Niels Neumann,
Christian Schäffer
Show abstract
A fiber-optic sensor for the detection of small refractive index changes is presented. The high sensitivity of the novel
miniaturized sensor concept is achieved by exciting of surface plasmon waves with a single cladding mode using a longperiod
fiber Bragg grating. This paper gives a brief description of the operating principle, design and fabrication of the
sensor. Sensor performance is discussed on the basis of initial experiments.
Improved performance of SPR optical fiber sensors with InN as dielectric cover
Show abstract
In this work, the performance of uniform-waist tapered optical fiber sensors based on SPR with Indium Nitride (InN) as
dielectric layer has been experimentally studied. The obtained results show that the overall performance in terms of
reliability, long term stability and sensitivity is improved. Furthermore, the dependence of the sensitivity with the
thickness of the dielectric layer is also studied, showing that increases as the thickness decreases while the well known
trend to excite the surface plasmons at longer wavelengths or higher refractive index of the outer medium is kept. Thus, a
novel application of the InN to optical fiber sensors is demonstrated. The use of this material would be of great interest to
produce new, improved, SPR-based devices for chemical and biological sensing.
An experimental evaluation of the behavior of SPR fiber sensors in absorptive medium when plasmons are tuned to absorption peaks: method for selective measurement
Show abstract
In this work we present experimental results that confirm the influence of an absorptive surrounding medium in the behavior
of conventional SPR fiber sensors. It can be observed that when a plasmon resonance coincides with a wavelength
absorbed by the medium, the depth of the dip is affected, as predicted in the simulations. The results are important from
the basic point of view, since the influence of absorptive medium in plasma waves has not been sufficiently studied up to
date and they can also be used as the basis for a new method of SPR-based refractometry selective to specific analytes
without the need of the addition of recognizing elements to the transducer.
Chemical sensing with an all-fiber reflection LSPR sensor
Show abstract
Previously, we developed an all-fiber reflection Localized Surface Plasmon Resonance (LSPR) sensor based on specular
reflection and LSPR from Au nanoparticles (NPs). The sensor was characterized with standard refractive index fluids.
We now demonstrate that this sensor can be used in chemical sensing applications by using it to monitor the refractive
index of Carbon dioxide (CO2) with refractive index from n=1.04 to n=1.36. In this experiment, the sensor presented a
resolution of approximately 0.02RIU and a sensitivity of at least -45nm/RIU. These results show that the all-fiber
reflection LSPR sensor is a viable method for chemical sensing.
Surface plasmon resonance refractive index fiber sensor with hole-assisted structure
Show abstract
A optical fiber with hole-assisted structure is proposed to construct the surface plasmon resonance (SPR) refractive index
sensor. The finite element method is utilized to analyze characteristics of the surface plasmon resonance sensor. The
effects of the thickness of metal films, fiber core size, and refractive index of liquid on the resonance wavelength are
investigated. The sensitivity of sensor is also given. The result shows that the resonance wavelength is sensitive to the
thickness of metal film and refractive index of liquid, while the resonance wavelength doesn't change basically when the
fiber core size. The proposed surface plasmon resonance sensor exhibits high sensitivity up to 10-4.
Development and sensitivity studies of a gold nanorod platform for a localized surface plasmon resonance based optical fibre biosensor
Show abstract
A localized surface plasmon resonance (LSPR) based optical fibre sensor using gold nanorods has been demonstrated,
showing a much higher sensitivity to the refractive index change surrounding the sensing area than that using gold
nanoparticles. In this work, a novel method has been employed to improve gold nanorod synthesis and immobilization
on the exposed surface area of an optical fibre core intended for sensor use. The device sensitivity, measured as a
function of the refractive index change, was found to be around 778nm/RIU (RIU=Refractive Index Unit), showing
considerable promise to be a better platform for label-free biosensors, monitoring the interaction between antibodies and
their antigens in a number of sensing applications in industry.
A novel fiber-tip micro-cavity sensor for high temperature application
Show abstract
A low cost fiber-optic micro-cavity interferometric sensor is presented. The micro-cavity is fabricated at the fiber
tip by splicing a silica capillary to a single mode fiber and then heating/melting the capillary to form a microsphere with
an internal air cavity. The sensor has small size and good mechanical strength, and may be used for pressure and
temperature measurement in high temperature environment.
Porous silicon-based optical fiber Fabry-Perot sensor for relative humidity determination
Show abstract
A fiber-optic relative-humidity sensor composed of two silver coating and a thick porous silicon film is proposed and
demonstrated for relative humidity sensing. The two Ag coatings are magnetically sputtered, with porous silicon
membrane sandwiched in between, which constructs a low-fineness Fabry-Perot sensing head. Experimental results show
that the interference fringe of the proposed porous silicon Fabry-Perot sensor shifts by 10.3 nm when relative humidity
increases from 11% to 97%. The linearity of interference fringe shift to relative humidity is averagely 0.9764 below 85%
RH. The proposed sensor is suitable for relative humidity sensing in the ambient environment.
Inspection technique for cleaved optical fiber ends based on Fabry-Perot resonator
Show abstract
We present a novel inspection technique for cleaved optical fiber ends based on the Fabry-Perot resonator. The technique
uses mainly laser diodes, an optical power meter, 3-dB coupler, and XY lateral adjustment stage. It can be achieved more
easily than current imaging processing that uses a charge coupled device camera and video monitor. The inspected fiber
end is considered failed or successful depending on whether both the measured return losses from the fiber end at two
wavelengths are equal to ~14.7 dB. Experimentally obtained fiber end images were in good agreement with scanning
electron microscope observation images. Thus, the proposed technique provides a simple and cost-effective way to
inspect cleaved optical fiber ends.
Fiber-optic Fabry-Perot sensor based on graded-index multimode fiber: numerical simulations and experiments
Show abstract
Numerical simulations based on the ray-transfer-matrix (RTM) method is realized for explaining the principle of a
graded-index multimode fiber (GI-MMF) based hybrid fiber Fabry-Perot (GI-FFP) sensor. It is verified by the
numerical simulations and experimental results that the high fringe contrast of the reflective spectrum of the
sensor is due to the periodic focusing effect of the GI-MMF. Experimental results are in good agreement with the
theory. A typical GI-FFP sensor is fabricated and its response to the external refractive index is measured with a
maximum sensitivity of ~160 dB/RIU.
Demodulation of micro fiber-optic Fabry-Perot interferometer using subcarrier and dual-wavelength method
Zengling Ran,
Yunjiang Rao,
Zhiwei Liu,
et al.
Show abstract
Subcarrier technology and dual-wavelength demodulation method are combined for tracking the cavity
length variation of a micro fiber-optic fabry-periot (F-P). Compared with conventional dual-wavelength
demodulation method, two operation wavelengths for demodulation are modulated with two different carrier
frequencies, respectively, and then injected into optical link connected with the F-P cavity. Light power reflected
for the two wavelengths is obtained by interrogating the powers of Fast Fourier Transform (FFT) spectrum at their
carrier frequencies. Because the light at the two wavelengths experiences the same optical and electrical routes,
measurement deviation resulting from the drift of optical and electrical links can be entirely eliminated.
1100°C fiber-optic high-temperature Fabry-Perot sensors fabricated by laser-micromachining
Show abstract
Two laser-machined high-sensitivity fiber-optic Fabry-Perot (F-P) high temperature sensors based on
sapphire and silica fibers are fabricated by laser-micromachining and demonstrated in this paper, respectively. The
temperature characteristics of the sapphire and silica fiber sensor are investigated over a temperature range from
100°C to 1100°C. Experiment result shows that the sapphire F-P sensor has a temperature sensitivity of ~50
pm/°C with a linearity of 0.999, which is 5 times higher than that of the silica F-P sensor.
Fiber-optic Fabry-Perot interferometer tip accelerometer fabricated by laser-micromachining
Zengling Ran,
En Lu,
Yunjiang Rao,
et al.
Show abstract
A novel fiber-optic tip accelerometer based on Fabry-Perot (F-P) interferometer is proposed and
demonstrated, with potential to operate under high temperature, in this paper. Such a tip accelerometer is directed
fabricated on a large cladding fiber end by using the 157nm laser-micromachining technology. With the
calibration of a micro electro mechanical systems (MEMS) accelerometer, the sensitivity of such a fiber-optic F-P
accelerometer is 1.764 rad/g. The minimum detective acceleration is estimated to be 20μg.
Fiber Fabry-Perot interferometer sensor for measuring resonances of piezoelectric elements
Show abstract
The development of a fiber extrinsic Fabry-Perot interferometer for measuring vibration amplitude and resonances of
piezoelectric elements is reported. The signal demodulation method based on the use of an optical spectrum analyzer
allows the measurement of displacements and resonances with high resolution. The technique consists basically in
monitoring changes in the intensity or the wavelength of a single interferometric fringe at a point of high sensitivity in
the sensor response curve. For sensor calibration, three signal processing techniques were employed. Vibration
amplitude measurement with 0.84 nm/V sensitivity and the characterization of the piezo resonance is demonstrated.
Temperature Raman laser sensor based in a suspended-core Fabry-Perot cavity and cooperative Rayleigh scattering
Show abstract
In this work, a simple scheme for a temperature fiber laser sensor is proposed. The temperature laser sensor is based in
the combination of a distributed mirror with a Fabry-Perot cavity. The distributed mirror is an outcome of the high Raman
gain in the dispersion compensating fiber. The Fabry-Perot interferometer presents a double function, as one of the
laser's mirrors and as the temperature sensing cavity. The proposed temperature laser sensor presents maximum output
power of ~2.7mW while providing a temperature sensibility of ~6pm/0C, in a 2000C range.
High-sensitivity salinity sensor realized with photonic crystal fiber Sagnac interferometer
Show abstract
We present a highly sensitive salinity sensor realized with a polyimide-coated polarization-maintaining photonic crystal
fiber (PM-PCF) based on a Sagnac interferometer configuration. The achieved salinity sensitivity is as high as 0.616
nm/M which is 37 times more sensitive than that of previous reported polyimide-coated fiber grating sensor. It has a low
temperature sensitivity of -0.0122 pm/°. The performance of the sensor in aqueous solution of NaCl with concentrations
up to 5.12 mol/L has been experimentally investigated. The proposed fiber optic salinity sensor is a promising candidate
for salinity measurement.
A hybrid Sagnac interferometer for discrimination of ambient index and temperature
Show abstract
A hybrid Sagnac interferometer with a D-shaped polarization maintaining fiber (PMF) and a fiber Bragg grating (FBG)
is proposed and experimentally demonstrated for simultaneous measurement of ambient index and temperature. Since
the core mode of the locally D-shaped PMF is directly interfaced to the external environment, the interference pattern of
the D-shaped-PMF-based Sagnac interferometer is immediately changed by the variation of external index and
temperature. The resonant wavelength of the FBG, however, responds only to the temperature change. Therefore, it is
possible to discriminate ambient index and temperature sensitivities by using the proposed hybrid Sagnac interferometer.
Long distance simultaneous measurement of bending and temperature based on a dual-wavelength Raman fiber laser
Show abstract
A simple scheme for simultaneous measurement of bending and temperature based on a dualwavelength Raman
fiber laser at a long distance of more than 50 km is investigated without additional light sources.
A Sagnac loop sensor for simultaneous strain and temperature measurement
Show abstract
A Sagnac loop sensor with a long-period grating (LPG) inscribed in polarization maintains fiber (PMF) for
simultaneous strain and temperature measurement is proposed. Taking using of the different responses of the LPG and
the Sagnac loop to strain and temperature, simultaneous measurement can be achieved by monitoring the wavelength
shifts and the intensity changes of resonance peaks. The experiments show that sensitivity of strain and temperature are
6.4×10-3 dB/με and 0.65 nm/°C, respectively.
Interferometric phase sensor using single-ended polarization maintaining fiber in Sagnac interferometer
Show abstract
An interferometric phase sensor is proposed and demonstrated for strain sensing based on a Sagnac
interferometer including polarization maintaining fiber (PMF). Since the conventional PMF Sagnac
interferometer includes a PMF in the loop by splicing both ends with the two ends of 50:50 coupler, it has
been difficult to apply the two-ended PMF in the practical applications. In this paper, we propose a simple
configuration by adding one more 50:50 coupler in the Sagnac loop to connect the PMF with one splicing
process for a remote sensing position. Instead of tracking the shift of periodic spectrum by optical spectrum
analyzer, higher sensitive method is proposed by interrogating a phase variation of the interferometric optical
signal from the modified Sagnac interferometer including single-ended PMF.
A novel magnetic field fiber sensor by using magnetic fluid in Sagnac loop
Show abstract
A novel magnetic field sensor by using magnetic fluid film in Sagnac loop is presented. The magnetic fluid introduces
controllable birefringence under external magnetic field inside the Sagnac loop to produce sinusoidal interference and
the corresponding transmission spectrum shifts with the change of external field strength. Sensitivity of 11.4 pm/Oe and
resolution of 0.88 Oe are achieved in the case of this proposed scheme.
Resonator micro optic gyro with double phase modulation technique using an FPGA-based digital processor
Show abstract
A resonator micro optic gyro (RMOG) with the proposed FPGA-based digital processor is set up. The double phase
modulation technique is applied to achieve high total carrier suppression. Rotation tests from ±0.1 °/s to ±5 °/s are tested,
where the processing circuit of RMOG is implemented by the instruments. The rotation test over a range of ±550 °/s has
been successfully obtained with all the processing circuit implemented in FPGA. To the best of our knowledge, these
results are the best results of RMOG ever demonstrated in silica resonator with the ring length as short as 7.9 cm.
Optical-frequency-comb based interrogation of fiber resonators
Show abstract
Strain sensing at the 10-13 level, from the mHz to the kHz frequency range, is performed using a fiber Bragggrating
resonator interrogated by an optical-frequency-comb stabilized laser. The optical-comb synthesizer is a
fs-pulsed fiber laser phase-locked to a quartz oscillator, which provides for a very high laser-frequency
stability. The comb teeth span over the 1510-1580 nm spectral interval. Therefore, the OFS is also used as a
coherent radiation source for fiber-loop cavity ring-down evanescent-wave spectroscopy of analytes diluted in
liquid samples.
A novel optical fiber current sensor using polarization diversity and a Faraday rotation mirror cavity
Show abstract
A novel high sensitivity optical fiber current sensor (OFCS) based on polarization diversity (PD) and a Faraday rotation
mirror cavity (FRMC) is proposed and demonstrated. The PD detection doubles the sensitivity and effectively removes
the DC background compared with the single-channel detection, while the FRMC suppresses the reciprocal birefringence
and amplifies non-reciprocal phase modulation caused by the current-induced magnetic field. Compared with the results
obtained by single-channel detection, a signal gain of 6dB and a signal-to-noise ratio improvement of over 30dB have been
achieved in the new scheme. A linear response is obtained for current amplitude as low as mA.
Offset errors caused by the resonance asymmetry in the waveguide-type optical passive resonator gyro
Show abstract
The resonance asymmetry in the waveguide ring resonator and its influence on the offset errors of the waveguide-type
optical passive resonator gyro (OPRG) are demonstrated experimentally and theoretically. The offset errors are produced
by the resonance asymmetry especially when the phase modulation spectroscopy technique is involved in the OPRG.
Modulation frequencies of both the clockwise and counterclockwise lightwaves are determined to decrease the offset
errors. The fundamental solution to eliminate the asymmetry influence on the OPRG is also proposed.
Microscopic multiple-point temperature sensing based on microfiber double-knot resonators
Show abstract
A novel fiber-optic sensor structure fabricated by cascading two optical microfiber knot resonators (MKRs) is
proposed and demonstrated in this paper. A theoretical analysis for describing the principle of such a microfiber
double-knot resonators (MDKRs) based sensing structure is given while an experiment is carried out to verify the
design. Experimental results show that high-precision and simultaneous multi-point temperature sensing in
micro-scale can be achieved by using this structure. Such a MDKRs based sensor also shows the potential for
achieving dual-parameter measurement to eliminate the cross-talk in small scale.
Interferometric humidity sensors based on microfiber knot resonators
Show abstract
In this paper, three fiber-optic interferometric humidity sensors based on silica/polymer microfiber knot resonators
(SMKR/PMKR) are reported. These tiny humidity sensors are directly fabricated by using silica/polymer microfibers
without any humidity-sensitive coating. The silica MKR has a humidity sensitivity of ~12pm/10% RH over a range from
14% RH to 60% RH, while the PMMA (poly-methyl methacrylate) MKR has a humidity sensitivity of ~88pm/10% RH,
over a range from 17% RH to 95% RH, and the PAM (Polyacrylamide) MKR with the highest sensitivity of ~270pm/%
RH over the range of 10% to 62%.
Dual-probe simultaneous measurements of refractive index and thickness with spectral-domain low coherence interferometry
Show abstract
An optical interferometric system for the simultaneous measurements of physical thickness and refractive group index is
implemented. The proposed system is based on a spectral-domain optical low coherence interferometry with two sample
probes facing to each other. The two-probe approach enables simultaneous measurements of thickness and group index
of a transparent sample. The average measurement errors were ~0.112 % in the physical thickness and ~0.035 % in the
group index, respectively.
Analysis of optical fiber interferometer sensor bonded to flat diaphragm for dynamic stress measurement at high temperature
Show abstract
We present a theoretical and experimental analysis of the magnitude of deflection of a flat diaphragm, supported at its
edge, with an interferometric sensor bonded on diaphragm surface and subjected to dynamic strain induced by varying
pressure. The results obtained are compared with a diaphragm not having a sensor bonded on its surface. A brief
description of the optical fiber position on diaphragm for a specific interferometric configuration is also presented.
Photonic crystal fiber interferometer for dew detection
Show abstract
A novel method for dew detection based on photonic crystal fiber (PCF) interferometer that operates in reflection mode
is presented in this paper. A large wavelength peak shift for the interference pattern is observed at the onset of dew
formation. The fabrication of the sensor head is simple since it only involves cleaving and splicing. By attaching a
thermoelectric cooler with temperature feedback, the fiber sensor demonstrated can be used as a dew point hygrometer.
Miniaturized fiber probe reflective interferometer sensor
Show abstract
We report a miniaturized fiber probe inline reflective interferometer (FPIRI) sensor,
with a several μ-micro-notch cavity fabricated for highly sensitive refractive index
measurement. Its sensitivity in liquid is ~100 nm/RIU (refractive index unit) near the
wavelength of 1550 nm with a high extinction ratio. This probe sensor is very compact, stable,
and cheap, offering great potentials for detecting inside sub-wavelength particles or biocells.
Inline core-cladding intermodal interferometer based on nano-coated photonic crystal fiber for refractive-index sensing
Show abstract
The paper presents a modification of the refractive-index (RI) response of a photonic crystal fiber (PCF) based
intermodal interferometer using a thin plasma-deposited silicon nitride (SiNx) overlay with a high refractive index. We
show that the film overlay can effectively change the distribution of the cladding modes and thus tune the RI sensitivity
of the interferometer. Thanks to the nano-coating we were able to increase RI sensitivity eightfold in the range required
for biosensors (nD~1.33). Due to the extreme hardness of SiNx films and their excellent adhesion to the fiber surface, we
believe that after the deposition the device can still maintain its advantages, i.e. lack of degradation over time or with
temperature.
All-fiber interferometric sensor of 150kHz acoustic emission for the detection of partial discharges within power transformers
Show abstract
An all-fiber interferometric acoustic emission (AE) sensor was designed for partial discharges (PD) and characterized
against typical PZT sensors (R15i). The device is based on a multi-layer fiber-optic probe and it is able to detect PD
ultrasound emission at 150 kHz. It may be placed next to the discharge source immersed in oil - or as an ultrasonic
hydrophone -, thus overcoming the difficulties of acoustic attenuation which are characteristic of the external detection
on the walls. The device provides suitable narrowband acoustic detection of the PD activity, like the PZT transducers
mounted on the exterior of the transformer tank. The results show similar sensitivity, but wider directivity of the fiberoptic
sensor in order to inspect large zones within the tank. It represents a simple and cheap alternative for detecting AE
and it is the base of a multi-channel heterodyne interferometer which will drive at least four sensors to provide
information for locating the source.
Delayed self-heterodyne interferometry using Faraday mirrors in a Michelson configuration
Show abstract
The use of Faraday rotator mirrors in a Michelson interferometer configuration is shown to
significantly improve resolution and coherence for delayed self-heterodyne interferometry.
Interferometric system controlled by virtual instrumentation for differential thermal analysis
Show abstract
This work describes the implementation of an optical fiber interferometric system for differential thermal analysis. The
system is based on a white light Mach-Zehnder configuration, with serrodyne phase modulation, to interrogate two
identical fiber Bragg gratings (FBG) in a differential scheme. Operation and signal processing with low cost digital
instrumentation developed in Labview environment enabled FBG temperature measurement with a ±0.012ºC resolution
nearly matching the performance of standard hardware. Preliminary results were obtained, where mixed samples of
acetone and methanol could be successfully identified, indicating the suitability of the system for high accuracy
differential thermal analysis using low cost instrumentation.
Tactical-grade interferometric fiber optic gyroscope driven with a narrow-linewidth laser
Show abstract
We report for the first time a tactical-grade fiber optic gyroscope interrogated with a laser instead of a broadband
source. The measured bias drift is 2.5 °/h and the random walk 0.016 °/√
h. This random walk is lower than
when the same gyroscope is interrogated with a broadband source, while the drift is only ~3 times higher.
This significant development was enabled by an appropriate choice of laser linewidth to mitigate backscattering
effects, and careful control of spurious reflections. The benefits of using a laser include a much higher scale factor
stability, lower power consumption, and lower component cost.
A simplified common-path autocorrelator based on Fizeau interferometer
Show abstract
We propose a simplified common-path autocorrelator based on Fizeau interferometer for quasi-distributed measurement.
A four-port fiber circulator is employed to connect broadband light source, fiber sensor array, Fizeau interferometer and
photodetector, constructing a most simple configuration and common-path between sensing and reference signals. This
common-path configuration of the autocorrelator can greatly reduce the polarization and dispersion mismatch between
sensing and reference signals. The use of circulator can also avoid reflective light from sensor array reentering into light
source, which can improve the stability and efficiency of the autocorrelator. The optimization of the autocorrelator is
theoretically discussed, and a seven-sensor autocorrelator is experimentally demonstrated. The common-path sensing
system is quite suitable for quasi-distributed measurement of strain and temperature in smart structures.
Dynamical interrogation of interferometric sensor arrays by a simple polarimetric setup
Show abstract
Numerous methods have been proposed for multiplexing interferometric sensors into large scale arrays. Previously we
described a low loss polarimetric sensor array based on a concatenation of high-birefringence fiber. It was interrogated
by a wavelength scanning laser and its output was measured by a polarization analyzer. Here we demonstrate how the
same source and detection system can be used to interrogate a different sensor array with increased sensitivity: a cascade
of fiber-optic Fabry-Perot interferometers. The auxiliary interferometer, needed for obtaining a synchronized linear
frequency grid, is implemented "in-line" and does not require an additional detection and digitizing circuitry. The
proposed approach, therefore, constitutes a simple and modular sensor array interrogation scheme in which different
arrays of sensors with significantly different sensitivities can be interchanged according to circumstances.
Compact photonic crystal fiber refractometer based on modal interference
Show abstract
A compact photonic crystal fiber (PCF) refractometer based on modal interference has been proposed by the use of
commercial fusion splicer to collapse the holes of PCF to form a Mach Zehnder interferometer by splitting the
fundamental core mode into cladding and core modes in the PCF. Collapsed of holes was done at the interface between
the single mode fiber and PCF, and the PCF's end. The shift of the interference fringes was measured when the sensor
was placed into different refractive index liquid. High linear sensitivity of 253.13nm/RIU with resolution of 3.950×10-5RIU was obtained.
Self-mixing interference in fiber ring laser and its multiplexing
Show abstract
New approaches for multiplexing self-mixing interference (SMI) in fiber ring laser (FRLs) are presented. The expression
of output powers with optical feedback in FRL with parallel dual-channel and multi-channel is analyzed. The gain
competition, the intensity alternation among different channels and the attainable performance are discussed. The
experimental results show good agreement with the theory. Therefore, two-channel and multi-channel sensing or
measurement will be realized simultaneously.
Matrix operators for complex interferometer analysis
Show abstract
A modeling methodology and matrix formalism is presented that permits analysis of arbitrarily complex interferometric
waveguide systems, including polarization and backreflection effects. Considerable improvement results from
separation of the dependencies on connection topology from the dependencies on the devices and their specifications. A
non-commutative operator and embedding matrices are introduced allowing a compact depiction of the salient optical
equations, and straightforward calculation of the amplitude and intensity transfer functions.
Simplified Brillouin optical time-domain sensor based on direct modulation of a laser diode
Show abstract
A novel kind of Brillouin optical time-domain sensor based on direct modulation of a laser
diode (LD) is demonstrated which is free from the use of any microwave device. The
Brillouin pump and the probe waves are alternately generated by the LD modulation, and an
optical time-domain analysis adopted for distributed measurement. Maps of Brillouin
frequency shift are obtained with a spatial resolution of 2 m and an accuracy of ±2 MHz in a
2 km optical fiber.
Impact of pump depletion on the determination of the Brillouin gain frequency in distributed fiber sensors
Show abstract
The energy transfer between the two interacting optical waves in a distributed sensor based on stimulated Brillouin
scattering can lead to a non-uniform spectral distribution of the pumping power after a long propagation. This results in a
spectrally distorted gain that biases the determination of the maximum gain frequency. A quantitative analytical model
gives an expression for the tolerable pump power change keeping the maximum bias within a given accuracy.
Distributed and dynamical Brillouin sensing in optical fibers
Show abstract
Employing stimulated Brillouin scattering (SBS), we present a novel method for the quasi-simultaneous distributed
measurement of dynamic strain along an entire Brillouin-inhomogeneous optical fiber. Following classical mapping of
the temporally slowly varying Brillouin gain spectrum (BGS) along the fiber, we use a specially synthesized and
adaptable probe wave to always work on the slope of the local BGS, allowing a single pump pulse to sample fast strain
variations along the entire fiber. Strain vibrations of tens of Hertz and up to 2KHz are demonstrated, simultaneously (i.e.,
using the same pump pulse) measured on two different segments of the fiber, having different static Brillouin shifts.
Long integral temperature Brillouin sensor for off- shore wind energy power supply lines
Show abstract
A hybrid Erbium-Brillouin fiber laser sensor to measure the temperature along 22 km fiber is proposed and
experimentally demonstrated. A multi-line laser oscillation is induced by the Brillouin gain of different concatenated
transducer fiber sections placed in the ring cavity. Integral temperature measurements of each fiber section are obtained
through each laser line. This sensor can be used to monitor the temperature of off-shore wind energy power cables.
BOTDA sensor with 2-m spatial resolution over 120 km distance using bi-directional distributed Raman amplification
Show abstract
In this paper we propose the use of optimized bi-directional distributed Raman amplification to enhance the operating
range of Brillouin optical time-domain analysis (BOTDA) sensors. In particular by combining high-power fiber-Raman
lasers and polarization-multiplexed Fabry-Pérot lasers operating at 1450 nm with low relative-intensity-noise (RIN), we
demonstrate distributed sensing (using first-order Raman amplification) over 120 km of standard single-mode fiber with
2 meter spatial resolution and with a strain/temperature accuracy of 45με/2.1°C respectively.
Experimental examination of the variation of the spontaneous Brillouin power and frequency shift under the combined influence of temperature and strain
Mohammad Belal,
Trevor P. Newson
Show abstract
We experimentally examine the validity of previous assumptions that the Brillouin coefficients describing the variation
of the power of the spontaneous Brillouin and its frequency shift with respect to either strain or temperature are
independent of the other parameter.
Evaluation of a high spatial resolution temperature compensated distributed strain sensor using a temperature controlled strain rig
Mohammad Belal,
Trevor P. Newson
Show abstract
We demonstrate a scheme which allows for temperature corrected distributed strain measurements under
environments involving simultaneous application of strain and temperature, with enhanced spatial (5 cms),
strain (66με) and temperature resolutions (1.9°C). The technique utilizes the combination of frequency based
BOCDA with Brillouin intensity measurements.
Simultaneous temperature and strain measurement with bandwidth and peak of the Brillouin spectrum in LEAF fiber
Show abstract
Leaf fiber's Brillouin gain spectrum characteristics such as peak power and line-width are studied under different strain
and temperature conditions. We compared these results with those of SMF and explained the similarities and differences.
They are attributed to the dependence of refractive index, density, acoustic velocity, effective length and effective area
on strain and temperature. Besides the acoustic waveguide structure is also applied to explain the different behaviors of
LEAF and SMF. Based on the linear relationships between the four peaks' line-width and strain/temperature the strain
and temperature errors of using each peak's Brillouin frequency shift and line-width are calculated. We achieved a strain
error of 36.91με and a temperature error of 1.84°C with a spatial resolution of 4m. This provides another way of
measuring the temperature and strain simultaneously using LEAF fiber's bandwidth and peak frequency.
Potential of Brillouin scattering in polymer optical fiber for strain-insensitive high-accuracy temperature sensing
Show abstract
We investigated the dependences of Brillouin frequency shift (BFS) on strain and temperature in a perfluorinated gradedindex
polymer optical fiber (PFGI-POF) at 1.55-μm wavelength. They showed negative dependences with coefficients of
-121.8 MHz/% and -4.09 MHz/K, respectively, which are -0.2 and -3.5 times as large as those in silica fibers. These
unique BFS dependences indicate that the Brillouin scattering in PFGI-POFs has a big potential for strain-insensitive
high-accuracy temperature sensing.
Expansion of spatial measurement range in a correlation based Brillouin optical sensing system
Show abstract
We propose a novel technique for expansion of spatial measurement range in a Brillouin optical
correlation domain analysis (BOCDA) sensor system. Unlike conventional BOCDA, which has only a
single correlation peak within the sensing fiber, the proposed scheme has multiple correlation peaks
within the sensing section, and enables us to obtain selectively the physical information at a position
corresponding to each correlation peak since the fiber under test consists of different kinds of fibers
with different Brillouin frequency shifts. Using the proposed technique, we have successfully
expanded a measurement range while maintaining the spatial resolution.
Coherent probe-pump-based Brillouin sensor for 100-um crack detection and 100-km distributed strain and temperature sensing
Show abstract
We present 100-μm crack detection and 100-km distributed strain and temperature sensing by fiber-optic distributed
strain and temperature sensor (DSTS) based on coherent interaction of probe-pump. The DSTS products have been
employed to detect cracks on ceramic by measuring the strain distributions along the surface of the ceramic and a
continuing long-term field monitoring of local temperature and stress changes in a 70-km buried fiber-optic cable.
Centimeter-range spatial resolution distributed sensing by BOFDA
Show abstract
We demonstrate both numerically and experimentally the possibility to bring the spatial resolution of Brillouin optical
frequency-domain analysis (BOFDA) distributed sensors in the cm-range. The numerical analysis is aimed to understand
the effects of acoustic wave modulation on the accuracy of BOFDA systems when operating with submeter spatial
resolution. We demonstrate that these effects lead to an error in strain/temperature estimation, which depends on the
amount of strain/temperature change, and on the peak searching algorithm applied to the acquired spectra. Experimental
measurements of BOFDA traces up to 3.5 GHz, equivalent to 3-cm spatial resolution, are presented and discussed.
Polarization pulling based on stimulated Brillouin scattering in a dual-pump configuration
Show abstract
Stimulated Brillouin scattering (SBS) amplification of probe signals is highly polarization dependent. Maximum and
minimum gain values are associated with a pair of orthogonal states of polarization (SOP) at the fiber output. Since the
maximum gain is much higher than the minimum, the output probe SOP is pulled towards that of the maximum
amplification. Polarization pulling is restricted, however, by pump depletion. In this work, we propose, analyze and
demonstrate a method for enhanced SBS polarization pulling, using two orthogonal pumps: the one amplifies the probe
wave whereas the other attenuates it. The method provides the same polarization pulling as that of a single amplifying
pump, however it is considerably more tolerant to depletion.
Reduction of measurement time in BOTDA sensors using wavelet shrinkage
Show abstract
A new method based on wavelet shrinkage is presented showing decreased measurement time for Brillouin optical timedomain
analysis (BOTDA) sensors. In BOTDA sensors the data acquired from measurements is contaminated with
multiple sources of noise requiring enhancement in order to extract the Brillouin gain spectrum (BGS) and find strain
and temperature. Conventional BOTDA sensors have used the very slow ensemble averaging technique which requires
hundreds of acquisitions of each time-domain waveform. In this paper, we enhance time-domain waveforms using
wavelet shrinkage before applying the ensemble averaging on them. This modification yields a significant reduction of
95% in the number of waveform acquisitions. Experimental results confirm the accuracy of the measurement based on
wavelet shrinkage and show that the proposed sensor has one of the shortest measurement times amongst BOTDA
sensors.
Self-heterodyne synchronous detection for SNR improvement and distributed Brillouin phase shift measurements in BOTDA sensors
Show abstract
We present a Brillouin optical time domain analysis (BOTDA) sensor that takes advantage of the enhanced
characteristics obtained employing self-heterodyne optical detection combined with synchronous RF demodulation to
increase the sensibility of the sensor and minimize non-local effects. We also perform for the first time to our knowledge
distributed measurements of the Brillouin phase shift in an optical fiber.
Intensity and phase noise caused by stimulated Brillouin scattering
Show abstract
Stimulated Brillouin scattering (SBS) induced noise is harmful to long-haul fiber sensing systems. We use the localized
fluctuating model to study SBS in a single-mode fiber (SMF) and obtain the relation between the intensity fluctuations
and the input power. Experimental results show that relative intensity noise (RIN) is small when the input power is
below the SBS threshold and increases dramatically at first and then becomes flat gradually when the input power is
above the threshold, which agrees well with the theory. We also use an unbalanced Michelson interferometer with the
optical path difference (OPD) of 1 m as well as the phase-generated carrier (PGC) technique to measure the phase noise
and find that the curves of phase noise versus input power at different frequencies are similar to that of RIN. We also
infer that the increase of the phase noise is mainly due to the broadening of the linewidth caused by SBS.
30cm of spatial resolution using pre-excitation pulse BOTDA technique
Show abstract
A pre-excitation pulse technique in Brillouin optical time domain analysis (PP-BOTDA) for enhancement of the spatial
resolution is shown. The technique here exposed is based on the pre-excitation of the stimulated Brillouin scattering and
the subtraction of the Brillouin scattering due to the intensity dc level present in the optical pulse. A main optical pulse
with 3ns of duration followed by a pulse of 40ns and half the intensity of the main one are used for obtaining 30cm of
spatial resolution. The spatial range is 3600m on a standard single mode optical fiber.
Quasi-static strain sensing using molecular spectroscopy
Show abstract
Steady developments in cost and reliability in fiber optic sensors have seen an increase of their deployment in numerous
monitoring and detection applications. In high-end applications, greater resolution is required, especially in systems
where the environment is quiet, but the signal is weak. In order to meet these requirements the most dominant noise
source, laser frequency noise, must be reduced. In this paper we present a quasi-static strain sensing referenced to a
molecular frequency reference. A DFB CW diode laser is locked to a fiber Fabry-Perot sensor, transferring the detected
signals onto the laser frequency and suppressing laser frequency noise. The laser frequency is then read off using an
H13C14N absorption line. Phase modulation spectroscopy is used to both lock the laser to the sensor and read off the
signals detected by the sensor. The technique is capable of resolving signals below 1 nanostrain from 20 mHz, reaching a
white noise floor of 10 picostrain at several Hz.
Sensing emulsification processes by Photon Density Wave spectroscopy
Show abstract
A key parameter for the monitoring of emulsification processes is the droplet size of the dispersed material. Due to
relatively high concentrations of the droplets in technical applications and their micrometer size these emulsions exhibit
strong light scattering. Photon Density Wave (PDW) spectroscopy is an innovative fiber-optical in-line technique for
precise determination of the optical absorption and scattering properties of such highly turbid samples. From the light
scattering properties (specifically the reduced scattering coefficient) mean droplet sizes can be quantified with a temporal
resolution on the minute-timescale. Investigation of the influence of emulsifier concentration and stirring speed on the
emulsification process demonstrate the excellent performance of PDW spectroscopy for fiber-optical in-line sensing
under these demanding spectroscopic conditions.
Laser induced breakdown spectroscopy algorithm using weights iteration artificial neural network
Show abstract
Laser-induced breakdown spectroscopy (LIBS) was applied to quantitative analysis of heavy metal pollution
elements in soil. The artificial neural network (ANN) algorithm is used to the processing of the complicated spectrum
lines of soil. In this paper we developed a new algorithm using weight iteration in the artificial neural network, so as to
decrease the training epochs remarkably. The spectrum line intensity of some elements, such as Cu, Cd, Al, Fe and Si,
were obtained. The limits of detection for trace elements Cu and Cd in soil were determined to be 42 and 5ppm,
respectively.
Phase-locking of commercial DFB lasers for distributed optical fiber sensing applications
Show abstract
The design of a phase/frequency detector-based optical phase-locked loop (PFD-OPLL) capable of locking two
commercial semiconductor distributed feedback (DFB) lasers for the purpose of making Brillouin Optical Time-Domain
Analysis (BOTDA) measurements is presented. Due to the aperiodic nature of the PFD transfer characteristic, the PFDOPLL
offers strong acquisition performance without requiring additional acquisition hardware. Design constraints due to
laser linewidths are relaxed by choosing a damping factor of 3.5 instead of 0.707. Loop stability is ensured by reducing
the loop propagation delay by as much as possible in hardware, and choosing the loop natural frequency such that the
loop bandwidth is below the FM phase reversal frequency of the laser. Results show stable lock performance at 11 GHz
with a phase noise of -70dBc/Hz at a 100 Hz offset, a capture range of 2.5 GHz and a tuning range of 3.3 GHz. These
specifications exceed the performance requirements of a BOTDA system.
500km remote interrogation of optical sensor arrays
Show abstract
We present remote measurements from a large-scale interferometric optical sensor system, using a 500km optical
transmission link between interrogator and sensor array, 3 times longer than the longest reported so far to our knowledge.
A phase noise floor of -80dB re 1 rad·Hz-0.5 peak was achieved (equivalent to 1 mPa·Hz-0.5). 256 sensors may be
interrogated via the link using a single fibre pair, making the system highly suitable for remote interrogation of large
scale sensor arrays for applications such as seismic and acoustic sensing. Eight amplified 125km spans using standard
Corning SMF-28 single mode fibre form the transmission link.
Fibre optic distributed differential displacement sensor
Show abstract
A Fibre Optic Distributed Differential Displacement Sensor is modelled and experimentally verified to determine
shape. Created using a steel tape, 9/125 μm single mode fibre, and adhesive, the FODDDS can be used to
determine shape or displacement of any object to which it is bonded. A circular shape is examined, and a radius
of curvature comparison yields an error of 2%. The sensitivity of the FODDDS, for the substrate thickness used
in this experiment, is shown to be 1.27 mm between adjacent data points, which corresponds to a radius of
curvature of 103 m.
Refractive index sensing based on Mach-Zehnder interferometer formed by three cascaded single-mode fiber tapers
Show abstract
We report the fabrication of a highly sensitive refractive-index sensor based on three cascaded single-mode fiber tapers,
in which a weak taper is sandwiched between the two tapers to improve the sensitivity of the sensor. Experimental
results show that the sensitivity of the device is 0.286 nm for a 0.01 RI change, which is about eleven times higher than
that of the normal two cascaded tapers MZ interferometer. Such kind of low-cost and highly sensitive fiber-optic
refractive index sensors will find applications in chemical or bio-chemical sensing fields.
Tunable narrow linewidth and stable frequency laser based on stimulated Rayleigh scattering in non-uniform optical fiber
Show abstract
A novel tunable and stable frequency fiber laser with ~4 kilohertz linewidth based on stimulated Rayleigh scattering
(STRS) in non-uniform optical fiber by using a broadband light source and a tunable filter is proposed in this paper for
the first time to our knowledge without ring laser configuration. Because of the variable core size and dispersion along
the fiber for non-uniform optical fiber, the threshold value of stimulated Brillouin scattering (SBS) was increased by
~7 dB; hence the phenomena of STRS can be clearly demonstrated. The frequency stability of the tunable laser only
depends on the tunable filter because the frequency of Rayleigh scattering in optical fiber is not sensitive to the change
of environmental conditions. Such kind of narrow tunable laser sources could find widely applications in optical
communication, optical sensing, optical precision metrology, and high-resolution spectroscopy.
Characteristics of stimulated Rayleigh scattering in optical fibers
Show abstract
The linewidth and the threshold of the stimulated Rayleigh scattering (STRS) in single mode fiber (SMF-28e), large
effective area fiber (LEAF) and polarization maintaining fiber (PMF) have been studied using heterodyne detection to
separate the Brillouin scattering with a fiber laser for the first time to the best of our knowledge. Experimental results
show that the linewidth of STRS and spontaneous Rayleigh scattering are ~9 kHz, ~10 kHz, and ~11 kHz, and ~25
kHz, ~30 kHz, and ~27 kHz for SMF-28e, LEAF and PMF, respectively. The threshold power for STRS for 2km
SMF-28e, 7km LEAF, and 100m PMF are 11dBm, 4.5dBm and 16.5dBm, respectively. The measured Rayleigh gain
coefficient is a 2×10-13m/W for SMF-28e. Because of the properties of narrower bandwidth and lower threshold power
of STRS in fibers, some of applications, such as narrower filter, could be realized.
Millimeter resolution distributed dynamic strain measurements using optical frequency domain reflectometry
Show abstract
We describe the use of swept wavelength interferometry for millimeter resolution dynamic fiber optic strain
measurements on a cyclically loaded aluminum coupon using single mode fiber. The interrogation method is based on
measuring the phase along the optical fiber and correlating the change in the phase derivative to strain via calibration.
This technique enabled data acquisition at 150 Hz at a 1mm spatial resolution. A maximum spatial and strain range of 8
ms and ±7,500 με, respectively, can be obtained. Measurements of the strain profile near a notch on the coupon
demonstrate the utility of the high spatial resolution made possible with this technique.
Chaotic lasers for elimination of low-frequency fluctuations of backscattered Rayleigh radiation in distributed fiber optical sensors
Show abstract
We have demonstrated suppression of low-frequency fluctuations of backscattered Rayleigh radiation in distributed fiber
optical sensors with chaotic single-longitudinal mode DFB and multi-longitudinal mode FP lasers subjected by
incoherent optical feedback. Significant decreasing of Rayleigh power variations up to 15-20 dB for 10-1000 Hz
frequency interval was recorded for both chaotic lasers. It was shown that chaotic DFB laser also efficiently restrain
stimulated Brillouin scattering in the test fiber. The results have important consequences for distributed fiber optical
sensors, which utilized Rayleigh signals.
Distributed temperature monitoring of long distance submarine cables
Martin Fromme,
Willi Christiansen,
Søren Valdemar Kjær,
et al.
Show abstract
Distributed temperature sensing (DTS) of long distance power cables is shown to provide valuable information for cable
design optimisation and proper operation of wind farms. The long range sensing is enabled by using the Raman-OFDR
(optical frequency domain reflectometry) technology in single-mode fibres. Raman-OFDR uses a modulated continuous
wave laser for detection. The low peak power minimizes stimulated Raman-scattering in single-mode fibres making
accurate temperature sensing over long distances feasible.
Hybrid TDM/WDM based fiber-optic sensor network for perimeter intrusion detection
Show abstract
A distributed fiber-optic sensor system is proposed and demonstrated for long-distance intrusion-detection, which
employs the hybrid time/wavelength division multiplexing (TDM/WDM) architecture. By utilizing 20 time zones and 6
wavelengths, the system contains up to 120 fiber sensing units (OSU), of which the distributed sensing distance is from 0
to 500m. So the whole sensing distance of this system could reach 60 km. The system has been demonstrated to run
stably exceed six months with the false alarm rate of less than 4%.
Improving the dynamic range in distributed anti-Stokes Raman thermometry by means of susceptibility asymmetry
Show abstract
In this paper it is verified, from experimental results, that the Raman susceptibility asymmetry is found as a key factor to
improve dynamic range in distributed anti-Stokes Raman thermometry sensor which operates in stimulated regime.
Improvements are discussed from experimental results of the spatial evolution of the anti-Stokes and Stokes branches for
different Raman anti-Stokes wavelengths.
The three point method for measurement of P-OTDR sensor
Show abstract
A new method for measurement of local birefringence is proposed for P-OTDR sensor,
based on the sequentially obtained three points of state of polarization (SOP) and a high speed
polarization analyzer. In this method only one input SOP is needed and the measurement results
are insensitive to the input SOP. The distribution of local birefringence vector along a 1km single
mode fiber was precisely measured with 2 cm accuracy, only once detection is enough for the
measurement.
Measurement of nonlinear refractive index by using input-output characteristics in OFRR nonlinear dynamics
Y. Imai,
S. Yamauchi,
H. Yokota,
et al.
Show abstract
A novel method for measuring nonlinear refractive index coefficient of an optical fiber
using input-output characteristics in nonlinear dynamics generated in an optical fiber ring
resonator is proposed and demonstrated for a pure silica core fiber. The nonlinear refractive index
coefficient n2=1.03×10-22[m2/V2] is obtained in the experimental demonstration.
Quasi-distributed vibration sensor based on polarization-sensitive measurement
Show abstract
In this paper we propose a novel kind of quasi-distributed vibration sensor based on the measurement of the polarization
state of light. Its principle is based on the combination of mechanical transducers -which transform the mechanical
perturbation into a birefringence variation- with fiber Bragg gratings. We show that several vibrations can be detected
and localized at each transducer position with a frequency resolution of 1.25 Hz.
A wide-area fiber sensor network with optical power supply
Show abstract
We demonstrate a wide-area fiber sensor network composed of sensor nodes driven by the power of transmitted
laser light. The sensor node produces optical signals by modulating a part of the laser light and sends it back to
the monitor. The developed sensor node was driven with an input optical power of 1.7 mW. The number of the
sensor nodes is also discussed theoretically. It is clarified that more than 1,000 sensor nodes can be placed along
an optical fiber line by using a high-power laser diode of 1 W.
Fiber-optic intrusion detection sensor for physical security system
Show abstract
The use of physical security technologies are becoming important to prevent intruders from stealing or vandalizing
property, and leaking personal information, as well as to secure personal safety. At many important facilities, fences are
installed along the boundary of the premises to prevent any intrusion. Vibration sensors need to be easily fixed to the
fences even around intricately shaped premises for monitoring a wide range of areas. We have proposed and
implemented a vibration sensor integrated with optical fiber and an optical interference system. To prevent any false or
missing alarms, we have also investigated a signal processing system that can be used to judge whether an alarm is
triggered by a natural phenomenon, small animals, or human intrusion.
A new multi-point sensing system based on optical pass switching and remote optical power supply
O. Ogawa
Show abstract
The author proposed a new multi-point optical sensing system (MPOSS), based on both technologies of optical pass
switching and remote power supply to the node using a high-power light source. In this system, the sensing nodes are
connected to trunk fiber lines through optical switches (OSW) and the optical pass to a desired node is configured by
switching. The light for power supply is received only by the node to be accessed, and significant power can be supplied
to the node. The proposed MPOSS allows us to employ various electrical sensors at the nodes without power equipment
(batteries et al.). In this paper, it is reported that the configuration and principle of the proposed MPOSS and the basic
demonstration results showing OSWs and an optical modulator at the node can be driven by a remote optical power
supply.
High performance wavelength demodulator for DFB fiber laser sensor using novel PGC algorithm and reference compensation method
Show abstract
We demonstrate a high performance wavelength demodulator for DFB FL sensor using novel PGC algorithm and
reference compensation method (RCM). An unbalanced fiber Michelson interferometer is employed and the phase
demodulation is accomplished by a digital PGC-Arctan-DSM algorithm. The RCM is adopted to eliminate the
environmental noise using a shielded and multiplexed DFB FL as a reference. Experimental results have demonstrated a
resolution of 3.5×10-7 pm/√Hz, a dynamic range of 120 dB @ 100 Hz, a THD of below 0.1 %, and a linearity of 99.99 %.
More than 50 dB reduction of the environmental noise has been experimentally achieved within 10-1000 Hz.
Low frequency acoustic response of a planar fiber laser cantilever in a fluid
Show abstract
The direct interaction of an acoustic field with a planar fiber laser cantilever in a fluid is investigated.
It is shown that a sensor based on this transduction mechanism responds to acoustic particle
velocity with a responsivity around 5×104 Hz/Pa yielding a resolution of 1.6 mPa/Hz1/2 at 100Hz, which is
adequate for many underwater acoustic applications. Issues related to developing a practical, miniaturized
sensor are discussed.
Acoustic sensor based on depressed cladding erbium doped fiber ring laser
Show abstract
This work describes a new type of acoustic sensor based on depressed cladding erbium doped fiber (DC-EDF) ring laser.
Due to the fiber amplification based on bending characteristics developed for S-Band uses, this sensor has high
sensitivity, broad dynamic range and wide bandwidth. It can be used to monitor parameters such as frequency, vibration
and acoustics. We describe the sensor characterization in S band in frequencies from 5 Hz to 50 kHz.
Ultrasound detection using a tunable low beat-frequency Er3+-doped DBR fiber laser
Show abstract
A compact low-beat-frequency dual-polarization distributed Bragg reflector (DBR) fiber laser for high-frequency
ultrasound detection has been demonstrated. The laser was fabricated in high germanium concentration, small-core
erbium-doped fiber with very small birefringence. Induced birefringence to the fiber during the UV inscription process is
small (~10-7) because of the small fiber core (4.2-μm) and consequently the laser beats at a low frequency of ~20 MHz,
making frequency down-conversion unnecessary. The beat frequency can be adjusted by controlling the side-exposure
time of the UV light irradiating the gain cavity, providing a simple approach to multiplex a large number of DBR fiber
lasers of different frequencies in series using frequency division multiplexing (FDM) technique.
Ultra thin fiber laser vector hydrophone
Show abstract
This paper presents a two-axis fiber laser vector hydrophone which uses a V-shaped flexed beam to enhance the
sensitivity and reduce the dimensions. Theoretical analyses of the sensitivity and frequent response are given. The key
parameters that determine the sensitivity and resonant frequency are discussed. The experimental results show an
acceleration sensitivity of 39.2 pm/g and 53.2 pm/g at the x, y axis respectively, a resonant frequency of about 310 Hz,
and a directivity resolution larger than 20 dB.
Full characterization and comparison of phase properties of narrow linewidth lasers operating in the C-band
Show abstract
We characterize and compare the performance of various commercially available lasers in terms of their absolute
frequency stability, lineshape, linewidth, and frequency noise. The frequency stability, linewidth and lineshape are
evaluated using an 'optical ruler' - a carrier-envelope stabilized optical comb. The frequency noise is measured over an
extended spectral range starting from 2 Hz. The performed analysis gives data necessary when deciding which laser to
use in a particular application.
Mode-locked multi-wavelength fiber ring laser using low frequency phase modulation
Show abstract
We demonstrate a stable and low noise mode-locked multi-wavelength ring laser for potential uses in optical sensors. The
ring laser cavity contains an all fiber phase modulator operating at 26.2 kHz, a Fabry-Perot comb filter, a band-pass filter
and a small core EDF, and passively mode-locked pulses at 5.62MHz rate are generated. This laser has a relative intensity
noise (RIN) value under -105 dB/Hz up to 1 GHz, and under -140 dB/Hz over 1 GHz. High peak power, high speed and
high temporal resolution of mode-locked multi-wavelength laser can be useful for diverse applications including
multiplexed interrogation of distributed sensor, spectroscopy and multi-spectral bio imaging.
Fast method for engineering Erbium-doped fiber lasers
Show abstract
The telecommunications industry and sensors require fast methods for engineering fiber lasers. In this work, using lowoptical-
power flat-top pulse excitations, it has been possible to determine both the attenuation coefficients and the
intrinsic saturation powers of doped single-mode fibers at 980 and 1550 nm. Laser systems have been projected for
which the optimal fiber length and output power have been determined as a function of the input power. Ring and linear
laser cavities have been set up, and the characteristics of the output laser have been obtained and compared with the
theoretical predictions based on the measured parameters.
50km long distance DFB fiber laser hydrophone system
Show abstract
We describe a new ultra long distance DFB fiber laser hydrophone system by using only one Raman pump laser
source with 1W output power at 1395nm and one section of erbium doped fiber. An all fiber backscattering suppression
module and 1550nm bandpass filter are used to reduce external reflection to DFB laser and remove unwanted the
remaining pump light in 1480nm band. A 50km DFB fiber laser hydrophone system has been successfully demonstrated
to detect acoustic signals.
L-band multiwavelength erbium-doped fiber ring laser for sensing applications
Show abstract
In this work, a novel single-longitudinal-mode (SLM) four-wavelength laser configuration for sensing applications in
L-band is proposed and experimentally demonstrated. This spectral region presents some advantages for the detection of
dangerous gases. The sensor system presented here is based on ring resonators, and employs fiber Bragg gratings to
select the operation wavelengths. The stable SLM operation is guaranteed when all the lasing channels present similar
output powers. It is also experimentally demonstrated that when a SLM behavior is achieved, lower output power
fluctuations are obtained.
Fiber laser vector hydrophone: theory and experiment
Show abstract
A novel fiber laser vector hydrophone (FLVH) based on accelerometers is presented. Three fiber laser accelerometers
(FLA), perpendicular to each other, are used to detect the acoustic induced particle acceleration. Theoretical analyses of
the acoustic sensitivity and the natural frequency are given. Experiment shows a sensitivity of 0.1 pm/Pa@100 Hz is
achieved, which results in a minimum detectable acoustic signal of 100 μPa/@Hz@100 Hz. Field demonstration shows
that the proposed vector hydrophone has good directivity.
Weak injection locked DFB semiconductor laser for optical fiber sensing
Show abstract
Two DFB semiconductor lasers are adopted as master and slave lasers to investigate the properties of the weak injection
locked DFB laser, such as the stable locking range, the phase noise and the power stability. A Brillouin/erbium fiber laser
pumped by the master DFB laser is injected into the slave DFB laser to validate the improvements of power stability and
spectral purity through the laser injection locking technology, which also demonstrates the feasibility of single frequency
extraction. The locked laser acts like a tunable narrow-band optical filter with central frequency and bandwidth decided
by the input signal. The experimental results give rise to some potential configurations useful for Brillouin distributed
fiber sensing and signal processing in microwave photonics.
Rayleigh Techniques and Frequency Domain Sensors
Long-range coherent optical frequency domain reflectometry and its applications
Show abstract
Recent progress on novel long-range coherent optical frequency domain reflectometry is described along with its
applications to diagnosing problems with optical fiber cables. The measurement range of a conventional C-OFDR is
limited to the coherence length of the laser used as a light source, since the phase noise of the laser degrades the
sharpness of the beat spectrum. We have developed phase-noise-compensated optical frequency domain reflectometry
(PNC-OFDR) to overcome this limit, by introducing a novel phase-noise compensation technique, and achieved a very
high-resolution measurement over the fiber link length. We describe the principle of PNC-OFDR and recent related
developments, and discuss its use in diagnosing issues with fiber networks.
Frequency domain simultaneous tone interrogation for faster, sweep-free Brillouin distributed sensing
Show abstract
We propose a frequency-sweep-free method for a SBS sensor, where the Brillouin shift is determined
without the need of sweeping the frequency of any of the optical waves. This is implemented by generating
simultaneous frequency tones in both probe and pump channels and by properly arranging their frequency
values. The closest tone to the Brillouin shift receives the most amplification, and thus the Brillouin gain
frequency center can be obtained from a single measurement. We experimentally demonstrate the feasibility
with CW probes and pumps. The extension to a fast sweep-free Brillouin optical time domain sensing is
performed through detailed simulations.
High performance Brillouin strain and temperature sensor based on frequency division multiplexing using nonuniform fibers over 75km fiber
Show abstract
We report a high-performance 75-km Brillouin optical time-domain analysis (BOTDA) based on frequency-division
multiplexing using multi-segment nonuniform fibers, realizing a spatial resolution of 1 m and an accuracy of 1°C/20Νε at
the end of 75 km, and a spatial resolution of 0.5 m and an accuracy of 0.7°C/14με; at the end of 50 km. Nonuniform
fibers with different Brillouin frequency shifts reduce the effective Brillouin amplification length to one resonant
Brillouin frequency segment rather than the entire sensing fiber, and thus the Brillouin interaction can be enhanced in
individual segments and signal-to-noise ratio can be improved without the pump pulse depletion or excess amplification
on probe pulse.
High precision, high sensitivity distributed displacement and temperature measurements using OFDR-based phase tracking
Show abstract
Optical Frequency Domain Reflectometry is used to measure distributed displacement and temperature change with very
high sensitivity and precision by measuring the phase change of an optical fiber sensor as a function of distance with
high spatial resolution and accuracy. A fiber containing semi-continuous Bragg gratings was used as the sensor. The
effective length change, or displacement, in the fiber caused by small temperature changes was measured as a function of
distance with a precision of 2.4 nm and a spatial resolution of 1.5 mm. The temperature changes calculated from this
displacement were measured with precision of 0.001 C with an effective sensor gauge length of 12 cm. These results
demonstrate that the method employed of continuously tracking the phase change along the length of the fiber sensor
enables high resolution distributed measurements that can be used to detect very small displacements, temperature
changes, or strains.
Ultra high dynamic range coherent optical time domain reflectometry employing frequency division multiplexing
Show abstract
We present coherent OTDR employing frequency division multiplexing and frequency demultiplexing by software
processing. We improved a 5-dB dynamic range against conventional coherent OTDR, and achieved a 100-dB dynamic
range with 218 measurements at a 1-km spatial resolution.
Vibration monitoring with high frequency response based on coherent phase-sensitive OTDR method
Show abstract
A coherent phase-sensitive OTDR system to detect distributed weak vibration is reported via heterodyne detection
combined with moving averaging and moving differential signal processing. The location and high frequency response
of weak vibration signal, such as pencil-break vibration which would match the characteristics of crack as a source of an
acoustic emission signals, are easily monitored. Our experimental results show that spatial resolution of vibration is
about 5m with 50 ns pump pulses, and the signal to noise ratio could be up to 6.5 dB. Also the frequency response could
be up to 1 KHz. Both consecutive multiple events at the same location and multiple simultaneous events at different
location with frequency components are identified which means our vibration testing system could be used for
distributed multiple vibration events detection.
New Fibers
Fibre lasers for photo-acoustic gas spectroscopy
Show abstract
We report here on the use of fiber lasers for recovery of gas absorption line shapes by photo-acoustic spectroscopy. We
demonstrate the principle of operation using an erbium-doped fiber, stabilized using a length of un-pumped doped fibre
as a saturable absorber. Intensity modulation of the laser output for phase sensitive detection is performed by modulation
of the pump current while the wavelength is scanned through the absorption line by a PZT on a fibre Bragg grating. This
avoids the distortions that arise in recovered signals due to simultaneous wavelength and intensity modulation, as is the
case with conventional DFB diode lasers. Furthermore, the near zero off-line signals with photo-acoustic spectroscopy
means that high modulation indices can be used with simple intensity modulation of the fiber laser output. The
modulation frequency is set to the acoustic resonance frequency of the gas cell and measurements are made on the P17
absorption line of acetylene at 1535.39nm showing good agreement with the theoretical line-shape profile.
Improved time response for polymer fibre Bragg grating based humidity sensors
Show abstract
In this work we experimentally investigate the response time of humidity sensors based on polymer optical fibre (POF)
Bragg gratings. By the use of etching with acetone we can control the diameter of POF based on poly (methyl
methacrylate) in order to reduce the diffusion time of water into the polymer and hence speed up the relative wavelength
change caused by humidity variations. A much improved response time of 11 minutes has been achieved by using a POF
FBG with a reduced diameter of 135 microns.
Two-photon excited fluorescence in praseodymium doped fibre and its application in distributed optical fibre sensing of temperature
Show abstract
Distributed temperature sensing based on time-correlated two-photon excited fluorescence (TPF) in doped fibre is
described. Counter-propagating laser pulses generate a TPF flash at the position of overlap which is scanned along the
fibre by a variable relative time delay. The flash is detected and analysed at one end. With the fluorescence power
being completely independent of excitation pulse duration and temporal profile, the sensor does not require ultrashort
excitation pulses for operation. There is potential for high spatial resolution as the length of the sensed region depends
only on pulse duration. TPF is reported in bulk glass doped with rare earths and in doped single-mode fibre. The
suitability of fluorescence transitions for sensing is discussed taking into account the temperature dependence of the
decay times, the location of the terminating energy level relative to the ground state, and the option of non-degenerate
TPF.
Poster Session: Microstructural Fiber, Novel Concepts, etc.
Very high polarimetric sensitivity to strain of second order mode of highly birefringent microstructured fibre
Show abstract
Microstructured fibres (MSF) or photonic crystal fibres (PCF) possess a number of unique properties enabling a wide
range of novel applications either in the telecommunication or in the sensing domain.
In this paper we show that highly birefringent (HB) MSF with a dedicated design that allows inscribing fibre Bragg
gratings in the MSF core can serve as pressure or stress transducers with extremely large sensitivity of second order
mode, while exhibiting a low sensitivity to temperature drifts. Therefore, Bragg gratings inscribed in such MSF may
offer a viable alternative to traditional optical fibre sensors of much lower stress sensitivity that require temperature
compensation mechanisms and that are not intrinsically capable of distinguishing stress and temperature.
Low cost pressure sensor system based on polarization-maintaining photonic crystal fiber operating at 850 nm with CCD interrogator
Show abstract
The use of polarization-maintaining photonic crystal fiber in a Sagnac interferometer configuration operating at 850 nm
shows large response to applied pressure. The sensor demonstrates a 300% improvement in sensitivity than when
operating at 1550 nm. Using wavelengths at the 850 nm window enable the use of low-cost CCD-interrogator which
also provides a much higher spectrum scanning speed than the much more expensive optical spectrum analyzers.
Single-mode 7-cell core hollow core photonic crystal fiber with increased bandwidth
Show abstract
We present two low-loss 7-cell core hollow-core photonic crystal fibers (HC-PCF) with intrinsic single mode properties
around 1550 nm. By reducing the number of surface modes within the bandgap these fibers can be operated close to the
short wavelength bandgap edge. It is well known that by omitting a core tube in HC-PCF fabrication of a surface mode
free bandgap can be achieved. We found by experimental as well as numerical, investigation that using a core tube with
a wall thickness reduced to between 60-70 % is sufficient to have a surface mode free short wavelength bandgap edge.
The transmission and mode properties of the fabricated fibers are examined experimentally and compared to numerical
calculations.
Side-hole polarization-maintaining photonic crystal fiber for hydrostatic pressure sensing
Show abstract
We propose a side-hole polarization-maintaining photonic crystal fiber (PM-PCF) with ultrahigh polarimetric sensitivity
to hydrostatic pressure. Modal birefringence B as large as 2.34×10-3 and polarimetric pressure sensitivity dB/dp as high
as -2.28×10-5 MPa-1 were achieved at 1.55 μm for the proposed fiber. Combining the advantages of both side-hole fibers
and PM-PCFs, the proposed fiber is an ideal candidate for future applications of pressure sensing.
Phase sensitivity to axial strain of microstrustured optical silica fibers
Show abstract
We compare, thanks to a Sagnac interferometer, the phase sensitivity to strain of different microstructured
optical silica fibers (MSF) that we design and fabricate. Our results show that when a same elongation is applied
to different MSF, the induced phase change is equal or lower than the one obtained for a standard fiber, showing
no advantage on this parameter for sensing applications.
A photonic crystal fiber temperature sensor based on forward stimulated fluorescence emission
Show abstract
In this paper, we present a novel optical fiber fluorescent temperature sensor based on photonic crystal fiber(PCF) and its
theory of forward stimulated fluorescence emission in PCF. It is realized by liquid filling in hollow-core PCF, the liquid
is of higher temperature coefficient of refractive index than that of silicon, and is mixed with fluorescent material.
Stimulating light and fluorescence propagating in the fiber are in the same direction. Because the band gaps of PCF are
modulated by temperature, besides the sensitivity of fluorescence, the stimulating light passing through the photonic
crystal fiber is also sensitive to temperature. Experiment results and theory modulation show that when PCF length is
shorter than an optimum length, stimulating light in fiber will increase and fluorescence will decline gradually with the
increase of temperature.
High-sensitive temperature sensor based on alcohol-filled highly birefringent photonic crystal fiber loop mirror
Show abstract
A novel compact temperature sensor based on a fiber loop mirror (FLM) combined with an alcohol-filled highlybirefringent
photonic crystal fiber (HiBi-PCF) is proposed and experimentally demonstrated. The output of the FLM is
an interference spectrum with many dips, of which the resonant wavelengths are quite sensitive to temperature because
the interference of the FLM is sensitive to the optical path difference due to the refractive index change of the filled
alcohol. Experimental results show that the temperature sensitivity reaches up to 5.42nm/°C for a 6.3cm long alcoholfilled
PCF used in the FLM.
Transversal-force sensor based on supercontinuum generation in photonic crystal fibers
Show abstract
A fiber optic force sensor system based on supercontinuum radiation is developed. Short pulse (175fs) generated from
mode-locked Erbium-doped fiber (EDF) laser was broaden and extended from 1300 to 1700nm after passing through
Photonic Crystal Fiber (PCF). The spectrum shift of this broadband continuum has a strong function to the change of
PCF birefringence induced by external force on PCF and exhibits a good sensitivity of 0.53604 nm/N and an excellent
repeatability. Thus, the proposed system is proven to be a novel instrumentation for the transverse force measurement
with many potential applications in smart structure.
Potential glucose monitoring of blood plasma using hollow core photonic crystal fibre
Show abstract
The ratio (ζ) of surface tension to viscosity of liquids can be determined using hollow core photonic crystal fibres (HCPCF),
and we show here techniques to determine ζ of glucose levels within fluids, of nano-litre quantities. We
demonstrate an optically integrated micro-capillary viscometer, to determine the concentrations of nano-litre solutions
based on properties of their flow within HC-PCF. The filling of the fibres with liquids within a given range of refractive
index will induce a shift in the photonic band gap of the fibre, allowing guidance of light at wavelengths that were
originally outside the bandgap of the HC-PCF.
Fabrication of polarization-maintaining photonic crystal fiber couplers using CO2 laser irradiation technique
Hirohisa Yokota,
Yusuke Ito,
Hiroki Kawashiri,
et al.
Show abstract
Polarization-maintaining photonic crystal fiber couplers (PM-PCFCs) are fabricated using CO2 laser irradiation
technique. We could successfully control the states of air holes in the tapered region of coupler by appropriately
adjusting the laser power in the elongation process of coupler fabrication. It was demonstrated that the air hole remaining
PM-PCFC exhibited polarization-splitting characteristics in which one of the polarization modes was transmitted to the
straight port and the other was transmitted to the cross port. It was also shown that the air hole collapsed PM-PCFC had
polarization insensitive coupling characteristics, where the polarizations of the transmitted lights at the output ports were
maintained.
A hollow-core photonic bandgap fiber polarization controller
Show abstract
A hollow-core photonic bandgap fiber polarization controller was made by applying
lateral pressures to three segments along the fiber. The applied lateral pressures result in variable
birefringence along the fiber, which modifies the state of the polarization. This approach may be
applicable to a hollow-core photonic bandgap fiber with little or no inherent birefringence.
Sensing characteristics of birefringent microstructured polymer optical fiber
Show abstract
We experimentally studied several sensing characteristics of a birefringent microstructured polymer optical fiber. The
fiber exhibits a birefringence of the order 2×10-5 at 1.3 μm because of two small holes adjacent to the core. In this fiber,
we measured spectral dependence of phase and group modal birefringence, bending losses, polarimetric sensitivity to
strain and temperature. The sensitivity to strain was also examined for intermodal interference observed in the spectral
range below 0.8 μm. Finally, we showed that the material transmission windows shift as function of the applied strain.
This shift has an exponential character and saturates for greater strain.
Thermo-optic effect of an index guiding photonic crystal fiber with elastomer inclusions
Show abstract
In this work, we demonstrate numerically and experimentally the temperature dependence of a photonic crystal fiber
(PCF) infiltrated with PDMS elastomer. We investigated the guiding properties of the PDMS-filled PCF and we present
the variation of the effective index and effective modal areas of the fundamental guiding mode at 633 and 1550 nm, for a
range of temperatures from 20°C to 75°C. Experimental measurements have shown an up to ~6% power recovery of the
bend-induced loss for a 6-cm long PDMS-filled PCF at 4 cm bend diameter.
Liquid crystal orientation control in photonic liquid crystal fibers
Show abstract
Similarly to liquid crystal displays technology in photonic liquid crystal fibers (PLCFs) a molecular orientation control
is a crucial issue that influences proper operation of PLCF-based devices. The paper presents two distinct
configurations: planar and radial escaped orientation of the LC molecules inside capillaries as well as methods of their
application to photonic liquid crystal fibers. Possibilities of LC orientation control influence both: attenuation and
transmitting spectra of the PLCF
The orienting method is based on creation of an additional orienting layer on the inner surface of the capillary or air
hole of the photonic liquid crystal fiber. Aligning materials used in the experiment are commercially available
polyimides SE1211 and SE130 which induce liquid crystal homeotropic and planar anchoring conditions. The orienting
layer increase an order parameter of the liquid crystal improving propagation properties and stability of photonic liquid
crystal fiber-based devices.
Index guiding photonic liquid crystal fibers for application in fiber optic sensing setups
Show abstract
Photonic liquid crystal fibers (PLCFs) can be categorized in two principal groups: index guiding PLCFs and photonic
bandgap PLCFs. In this paper we focus on index guiding PLCFs in which effective refractive index of the
micro-structured cladding filled with liquid crystal is lower than refractive index of the fiber core. In such fibers
broadband propagation of light is observed and also effective tuning of guiding properties is possible (i.e. birefringence,
polarization dependent losses or attenuation tuning). Such fibers could be used for dynamic control of light in various
fiber optics systems, including optical fiber sensing setups.
Photonic crystal fiber integrated microfluidic chip for highly sensitive real-time chemical sensing
Show abstract
Photonic crystal fibers (PCFs), although a highly effective platform for sensing, encounter difficulties with coupling as
well as infiltration and evacuation. A PCF integrated microfluidic chip has therefore been fabricated to demonstrate
improved coupling for real-time chemical sensing. Furthermore, an extremely sensitive dip-shifting analysis was
employed for the detection regime. Results eventually demonstrated its notable sensitivity and a refractive index
resolution of 10-7 RIU, rendering it suitable for utilization in highly sensitive sensing applications.
Photonic crystal fiber couplers based on large mode area fibers
Show abstract
The comparison of two types of photonic crystal fiber coupler (PCFC) based on LMA8 and LMA10 fibers are presented
in this paper. The couplers preparation process based on biconical fiber technique without air-holes collapsing. The same
parameters of elongation process have given slightly different results. The LMA10-PCFC has stronger polarization
dependence and many points with 50x50 coupling ratio in range 800 - 1600nm. The LMA8-PCFC has less polarization
sensitivity and better spectral characteristic in range 1500 - 1600nm as well as lower losses. It is observed that 50x50
coupling regions appear in second and third telecommunication windows.
Enhancing the sensitivity of liquid refractive index sensor based on slow light photonic crystal waveguide
Yong Zhao,
He Huang,
Qi Wang
Show abstract
This paper designed a high sensitivity refractive index sensor based on two-dimensional square-lattice slow light
photonic crystal waveguide. This structure based on Mach-Zehnder interferometer (MZI) which can be widely used in
measuring the refractive index of liquid. The resolution of this sample structure can reach 7×10-7 RIU. This kind of
sensor can be integrated with electronic systems to measure the refractive index of gas or fluid.
Hybrid photonic crystal fiber sensing of high hydrostatic pressure
Marcos A. R. Franco,
Valdir A. Serrão,
Tânia R. Pitarello,
et al.
Show abstract
The opto-mechanical response of Hybrid Photonic Crystal Fiber (HPCF) with Ge-doped inclusions is numerically
modeled for high hydrostatic pressure sensing purpose. A typical photonic crystal fiber (PCF) consists of a silica solidcore
and a cladding with a hexagonal lattice of air-holes. The HPCF is similar to the regular PCF, but a horizontal line of
air-holes is substituted by solid high index rods of Ge-doped silica. The optical guidance in HPCFs is supported
combining two physical effects: the modified total internal reflection and the photonic bandgap. In such fibers, the Gedoped
inclusions induce residual birefringence. In our analysis, we evaluate the susceptibility of the phase modal
birefringence and group birefringence to hydrostatic pressure. The analyses were performed at a photonic bandgap with
central wavelength near to 1350 nm. The polarimetric pressure sensitivity is about 10 rad/MPa x m at λ = 1175 nm.
Intensity modulated temperature sensor based on the photonic crystal fibers filled with magnetic fluid
Show abstract
We propose a photonic crystal fiber (PCF) temperature sensor that is based on intensity modulation by
magnetic fluid (MF) filling of air holes with index-guiding PCF. Temperature characteristic of MF-filled PCF is
investigated without magnetic field and with weak magnetic field. The results show that light is still guided by
total internal reflection (TIR) in this device because MF has a smaller refractive index than the material in the
fiber core; the transmission power of the MF-filled PCF is used as the sensor signal to investigate its
temperature properties. The temperature sensitivity of transmission power was experimentally determined to
be 0.06dBm/oC for a 10cm-long PCF without applying magnetic field.
Colloidal photonic crystals self-assembled onto the optical fiber substrates
Show abstract
We report the experimental demonstration of colloidal crystal deposited on the end face of fiber, as well as the side
cladding. The colloidal photonic crystals were fabricated through isothermal heating evaporation-induced self-assembly.
The resulted samples were characterized structurally by scanning electronic microscope (SEM) and optically by
transmission spectra analyzer. A moderately transmission dip at 1543 nm and 1546 nm wavelength coincides with the
photonic band gap expected for the 710 nm silica microspheres.
Bending effect on fiber optic evanescent absorption sensor for sensitivity enhancement in hetero-core structured fiber optic
Show abstract
Hetero-core structured fiber optic was applied to evanescent field absorption spectroscopy. The sensing part of the fiber
optic was immersed in a dye solution, then the bending was applied to the fiber optic probe, and propagating loss spectra
were measured. The effects of refractive index of the dye solution and the degree of the bending to the sensor part were
studied. According to increasing of the degree of bending, the peak strength of the spectra of the dye increased. This is
because that the increasing of the bending degree changes the angle of incidence in the propagating ray following the
evanescent wave is generated effectively, hence the number of the dye molecules that can interact with the evanescent
wave increases. As a result, the sensitivity enhancement of the peak strength was performed. In addition, the increase of
the refractive index of the dye solution enhanced the peak intensity in the absorption spectra. It has been shown that the
sensitivity enhancement of the fiber optic sensor would be performed by physical shape control and physical property of
the solution such as refractive index.
Multimodal interference based on large-core air-clad photonic crystal fibres for simultaneous measurement of multiparameters
Show abstract
This work describes a large-core air-clad photonic crystal fibre-based sensing structure that is sensitive to refractive
index, temperature and strain. The sensing head is based on multimodal interference, and relies on a single mode - largecore
air-clad photonic crystal fibre - single mode fibre configuration. Using two distinct large-core air-clad PCF
geometries it is possible to obtain an optical spectrum with two dominant loss bands, at wavelengths that have different
sensitivities to physical parameters. This characteristic is explored to demonstrate a sensing head that permits the straintemperature
discrimination functionality. It is also shown the large-core air-clad photonic crystal fibre can be applied to
implement a sensing head sensitive to the water refractive index changes induced by temperature variations.
Wearable motion capturing with the flexing and turning based on a hetero-core fiber optic stretching sensor
Show abstract
In recent years, motion capturing technologies have been applied to the service of the rehabilitation for the physically
challenged people and practicing sports in human daily life. In these application fields, it is important that a measurement
system does not prevent human from doing natural activity for unrestricted motion capture in daily-life. The hetero-core
optic fiber sensor that we developed is suited for the unconstrained motion capturing because of optical intensity-based
measurement with excellent stability and repeatability using single-mode transmission fibers and needless of any
compensation. In this paper, we propose the development of wearable sensor enables unconstrained motion capture
systems using the hetero-core fiber optic stretching sensor in real time, which satisfy user's requirements of comfort and
ubiquitous. The experiments of motion capturing were demonstrated by setting the hetero-core fiber optic stretching sensor
on the elbow, the back of the body and the waist. As a result, the hetero-core fiber optic stretching sensor was able to detect
the displacement of expansion and contraction in the optical loss by flexion motion of the arm and the trunk motion. The
optical loss performance of the hetero-core fiber optic stretching sensor reveals monotonic characteristics with the
displacement. The optical loss changes at the full scale of motion were 1.45dB for the motion of anteflexion and 1.99 dB
for the motion of turn. The real-time motion capturing was demonstrated by means of the proposed hetero-core fiber optic
stretching sensor without restricting natural human behavior.
A hetero-core fiber optic smart mat sensor for discrimination between a moving human and object on temporal loss peaks
Show abstract
In this paper, we propose discrimination method between a moving human and object by means of a hetero-core fiber
smart mat sensor which induces the optical loss change in time. In addition to several advantages such as flexibility, thin
size and resistance to electro-magnetic interference for a fiber optic sensor, a hetero-core fiber optic sensor is sensitive to
bending action of the sensor portion and independent of temperature fluctuations. Therefore, the hetero-core fiber thin
mat sensor can have a fewer sensing portions than the conventional floor pressure sensors, furthermore, can detect the
wide area covering the length of strides. The experimental results for human walking tests showed that the mat sensors
were reproducibly working in real-time under limiting locations the foot passed in the mat sensor. Focusing on the
temporal peak numbers in the optical loss, human walking and wheeled platform moving action induced the peak
numbers in the range of 1 - 3 and 5 - 7, respectively, for the 10 persons including 9 male and 1 female. As a result, we
conclude that the hetero-core fiber mat sensor is capable of discriminating between the moving human and object such as
a wheeled platform focusing on the peak numbers in the temporal optical loss.
Detection of soil gravity water with hetero-core optical fiber sensor
Norikazu Kumekawa,
Kazuhiro Watanabe
Show abstract
It is well known that soil water at a farm land seriously affects on growth and quality of crops. Therefore, although
several methods for monitoring of soil water have been developed. We developed a hetero-core structured optical fiber
Surface Plasmon Resonance (SPR) sensor coated with gold thick layer for sensing a drop of soil gravity water. We set
the sensor at 5 cm in depth from the top of soil and connected it to both a LED light source and a power meter. As the
result, the loss in light going through inside of the optical fibers became from 0.06dB to 1.21dB in 10-60 seconds after
watering, and the gain in light became from 0.03dB to 0.17dB in a matter of time after detection. According to the
result, it was proved that to detect soil gravity water is possible and in soils the detection ability of the sensor can return
which is caused by evaporating of water on the surface of the sensor by air in a soil.
Effect of doping swelling polymer cladding with phthalocyanine dye in plastic optical fiber humidity sensors
Show abstract
We have developed and tested plastic optical fiber (POF)-type humidity sensors, which consist of a dye-doped
swelling polymer cladding. POF-type humidity sensors consist of a hydroxyethyl cellulose or polyvinylpyrrolidone
(PVP) cladding layer that surrounds a poly(methyl methacrylate) core. The operation of these sensors is based on the
change in refractive index caused by swelling of the cladding layer. To improve the sensitivity of the humidity sensor,
we have investigated the effect of doping the cladding polymer with phthalocyanine dye. The results indicate that the
POF-type humidity sensor using PVP is three times more sensitive for relative humidities above 80% when the dyedoped
swelling-polymer cladding is used.
Low-cost, non-contact displacement sensor based on plastic fiber bundle
Show abstract
The article presents the state-of-the-art realization of a low-cost, non-contact displacement sensor based on plastic optical
fibers. The sensor head makes use of 7 fibers, arranged in a bundle configuration, to detect small displacements on a
moving target; the sensing systems can compensate variations to target reflectivity. Two advanced features have been
implemented: an optimization of the fiber bundle enables to improve the accuracy up to 2.7 times, and a Monte Carlo
simulation provides a detailed description of the system and enables surface mapping. Experimental result show an
accuracy of 7.5 μm on a range of 2.5 mm with reflectivity compensation, and of 2.4 μm on a range of 5 mm without
compensation.
Self-repairing polymer optical fiber sensor
Show abstract
This article presents experimental demonstrations of a self-repairing strain sensor waveguide created by self-writing in a
photopolymerizable resin system. The sensor fabricates between two multi-mode optical fibers via lightwaves in the
ultraviolet (UV) wavelength range and operates as a sensor through interrogation of the power transmitted through the
waveguide in the infrared (IR) wavelength range. After failure of the sensor occurs due to loading, the waveguide rebridges
the gap between the two optical fibers through the UV resin. The response of the original sensor and the selfrepaired
sensor to strain are measured and show similar behaviors.
Twisted optical microfiber for refractive index sensing
Show abstract
In this paper, a simple, compact and robust refractive index sensor has been developed, which is constructed by
twisting a pair of silica microfiber to form a coupling device. The transmission spectrum of the device is highly sensitive
to the surrounding refractive index and the highest sensitivity of -1665nm/RIU (refractive index unit) can be obtained at
the refractive index value of 1.3605 for the fibers with diameter of 2.1μm. The developed sensor device is easy to
construct, of low cost and compatible with optical fiber system.
Bend sensors based on periodically tapered soft glass fibers
Yiping Wang,
David Richardson,
Gilberto Brambilla,
et al.
Show abstract
We demonstrate a technique for tapering periodically an all-solid soft glass fiber consisting of two types of lead
silicate glasses by the use of a CO2 laser and investigate the bend sensing applications of the periodically-tapered
soft glass fiber. Such a soft glass fiber with periodic microtapers could be used to develop a promising bend sensor
with a sensitivity of -27.75 μW/m-1 by means of measuring the bend-induced change of light intensity. The proposed
bend sensor exhibits a very low measurement error of down to ± 1%.
Effects of aluminum doping concentrations on radiation sensitivity of erbium-doped fibers
Show abstract
The dependence of radiation induced attenuation (RIA) on Al concentrations was investigated for
γ-irradiated EDFs doped with different Er, Al and Ge concentrations. The dependence of RIA on dose was
found well fitted by power law, and linear dependence of adjusted α on Al concentrations was verified. When
the Al concentration was as low as 0.11%, an unknown RIA band with absorption peak around 800 nm was
observed, which might be related to Erbium ions.
Endoscopic optical coherence elastography using acoustic radiation force and bending vibration of optical Fiber
Show abstract
We investigate endoscopic optical coherence elastography with micro-scale resolution using acoustic radiation force. The
endoscopic optical scanner has vibration of an optical fiber for scanning the measurement light from an optical coherence
tomography (OCT) system to sample tissue. The optical fiber with the length of mechanical resonance condition is vibrated
in the bending mode using a cylindrical piezoelectric actuator driven by the phase-shifted voltages, and the output light
from the optical fiber end is collimated by a small lens. The prototype of the scanner probe is 1 mm in diameter and
20 mm in length. Stress in the tissue is caused due to acoustic radiation force which is induced by the difference of acoustic
energy density at the interface of the propagating media using a focused transducer. The deformation of the tissue sample
is measured by the swept source OCT with the depth-scanning rate of 20 kHz and the depth resolution of 9 μm. The
displacement and the strain are calculated with the cross-correlation detection using the images before and after applying
the force. The strain is slowly relaxed after removal of the force, and the time-varying curve is theoretically modeled. We
demonstrated the measurement and the imaging of strain distribution with frame rate of 50 fps.
Fiber-optic confocal microscopy using a miniaturized needle-compatible imaging probe
Show abstract
We report on the design and implementation of a 350 μm-diameter confocal imaging probe based on gradient-index
(GRIN) optics and a fiber-based scanning arrangement. The form factor of the probe is such that it can potentially be
inserted into a 22-gauge hypodermic needle to perform high-resolution confocal fluorescence imaging in solid tissues.
We introduce a simple scanning arrangement based on lensed fiber, which eliminates off-axis aberrations induced by
conventional scanning optics and is suitable for integration into a compact hand-held unit. We present the details of the
optical design and experimental verification of the performance of the optical system. The measured lateral resolution of
~700 nm is in agreement with the optical design and is the highest resolution reported for a confocal fluorescence
imaging probe of this size. Further, we demonstrate the imaging capability of the probe by obtaining high-resolution
images of fluorescently labeled muscle fibers.
Temperature monitoring of superconducting wire for quench detection
Show abstract
Multipoint temperature measurement of the superconducting wire was demonstrated to detect quench behavior utilizing a
multiplexed fiber Bragg gratings sensor. The sensor was directly attached on the wire to measure actual wire temperature
during the quenching. Quench propagation was successfully detected by measuring delay time of temperature increase
on each grating.
Ferrule-top cantilever optical fiber sensor for velocity measurements of low speed air flows
A. Cipullo,
G. Gruca,
K. Heeck,
et al.
Show abstract
We present the application of a ferrule-top cantilever optical fiber sensor to measure the velocity of low speed air flows.
The sensor is statically characterized against a Pitot tube in a small wind-tunnel and both probes are facing the flow in its
laminar region. The ferrule-top sensor is equipped with a single-wavelength interferometric readout and it shows good
sensitivity and short-term repeatability, despite the fact that the geometry and the read-out are not optimized.
In-situ monitoring of carbon dioxide emissions from a diesel engine using a mid-infrared optical fibre sensor
Show abstract
A robust optical fibre based CO2 exhaust gas sensor operating in the mid infrared spectral range is described. It is
capable of detecting on board carbon dioxide (CO2) emissions from both diesel and petrol engines. The optical fibre
sensor is not cross sensitive to other gaseous species in the exhaust such as water vapour (H2O), carbon monoxide (CO),
oxides of nitrogen (NOx) or oxides of sulphur (SOx).The response of the sensor to carbon dioxide present in the exhaust
of Fiat Croma diesel engine are presented.
Low concentration fluorescence sensing in suspended-core fibers
Show abstract
We present improvements to fluorescence sensing in microstructured optical fibers that result in significantly
improved sensitivity relative to previously published results. Concentrations of CdSe quantum dots down to 10 pM
levels have been demonstrated. We show that the primary limitation to the sensitivity of these systems is the
intrinsic fluorescence of the glass itself. We investigate alternative architectures for improved sensitivity by
separating the excitation and capture in to separate cores within a single fiber
Modeling of polarization mode coupling involved in a capillary optical fibre sensor
Show abstract
Theoretical and experimental work is reported on a distributed polarimetric fibre optic sensor designed for application in
capillary gas chromatography. Emphasis is on the improvement of the modeling of the polarization mode coupling
mechanism so as to get not only qualitative (vapor identification), but also quantitative (vapor concentration)
information from the analysis of a time-modulated signal transmitted through a polarizer at the end of a custom capillary
fibre.
Magnetic field sensing using D-fiber coupled Bi:RIG slab
Show abstract
Ultra small magnetic field sensors are created using magneto-optic slab waveguides coupled to optical fiber. The
magneto-optic material used is bismuth-doped rare earth iron garnet (Bi:RIG). By etching close to the core of D-type
optical fiber and attaching a magneto-optic material, light transfers from the fiber to the slab waveguide at specific
wavelengths. The wavelengths that couple depend on the refractive index of the slab that changes in the presence of a
magnetic field. When a field is applied, the wavelength coupling shifts and a resulting change in power can be detected.
The sensors reported in this paper detect magnetic fields as low as 11 A/m.
Biosensor application of resonance coupling to thin film planar waveguides on side-polished optical fiber
Show abstract
Optical resonance coupling between a side-polished fiber and thin film waveguides has been investigated in the presence
of biochemical adsorbates. The shift of the resonance wavelengths was found to be highly sensitive to the capture of
target DNA recognition elements with Au nanoparticle markers, allowing for a sensitivity limit of 10 particles on the
side-polished fiber core area (2000 μm²) during on-line measurements using a polychromator spectrometer.
Distance displacement measurement with two-photon absorption process in Si-APD and high-speed optical millimeter wave scanner
Show abstract
A high-speed optical millimeter wave scanner has been developed and introduced into the distance
displacement measurement based on two-photon absorption (TPA) process in a Si-APD. The TPA-based
distance displacement measurement can measure the displacement of an object at 10 mm to 10 km away in
principle. The measurement for the long distance of 10 m to 10 km was already realized by using intensity
modulated light with a modulation frequency range of 10 GHz in the last study. The high-speed optical
millimeter wave scanner developed in this study scanned over 100 GHz in 10 ms at its highest speed. We have
successfully measured the short distance of 10 mm with a data acquisition time of 1 s and an accuracy of
6.34×10-3 .
Stress monitoring in a maxilla model and dentition
Show abstract
Fiber Bragg gratings were used to measure stress caused by the orthodontic appliance in an experimental model
reproducing the maxilla and dentition. This study brings light to the understanding of the way forces are dissipated on the
dentition and propagate to the adjacent bone. Results show deformations on the order of 4 με and a linear relationship
between strain and the applied load in the incisor, canine and molar teeth.
Development of an integrated fibre optic sensing network for a composite rudder
Show abstract
This paper outlines the various steps considered in the design, development and application of a network of 294 optical
fibre based strain sensors on a glass fibre reinforced rudder for a mine counter measures vessel. The sensing array is
designed for use together with a vibration-based analysis tool to be implemented as an in-service structural health
assessment system.
Fibre optic sensors for high speed hypervelocity impact studies and low velocity drop tests
Show abstract
The initial aim of this project was to develop a non-contact fibre optic based displacement sensor to operate in the harsh
environment of a 'Light Gas Gun' (LGG), which can 'fire' small particles at velocities ranging from 1-8.4 km/s. The
LGG is used extensively for research in aerospace to analyze the effects of high speed impacts on materials. Ideally the
measurement should be made close to the centre of the impact to minimise corruption of the data from edge effects and
survive the impact. A further requirement is that it should operate at a stand-off distance of ~ 8cm. For these reasons we
chose to develop a pseudo con-focal intensity sensor, which demonstrated resolution comparable with conventional
PVDF sensors combined with high survivability and low cost. A second sensor was developed based on 'Fibre Bragg
Gratings' (FBG) which although requiring contact with the target the low weight and very small contact area had
minimal effect on the dynamics of the target. The FBG was mounted either on the surface of the target or tangentially
between a fixed location. The output signals from the FBG were interrogated in time by a new method. Measurements
were made on composite and aluminium plates in the LGG and on low speed drop tests. The particle momentum for the
drop tests was chosen to be similar to that of the particles used in the LGG.
Evanescent-wave fiber-optic sensor: on power transfer from core-cladding interface to fiber end-face
Show abstract
In this paper, the enhancement of collection efficiency in fiber-optic evanescent-wave (EW) sensors is studied. Both
theory and experimental results are presented. The theory is based primarily on ray optics, but for the sake of simplicity
and accuracy, wave optics is also considered. Fluorescent light is coupled into the core of a partly unclad multimode
fiber via EW. Most power is carried to the unclad end-face by tunneling modes. Reflection from this rough end-face,
which is modeled as a diffuse source, mixes the initial modes. Bound rays also play an important role, carrying the
power to the other end-face. The amount of output power of the bound rays there is calculated. We also study the output
power when the end-face is smooth. The comparison of these two cases of output power shows that the rough end-face
enhances the collection of coupled evanescent waves.
Influence of the lamination process on the strain sensitivity of the fiber sensors embedded in composite materials
Show abstract
Fiber-optic sensors based on highly birefringent (HB) polarization-maintaining (PM) fibers represent a promising
generation of sensing devices also known as polarimetric fiber sensors. They utilize polarization (phase) modulation
within fibers to sense external perturbations [1]. HB polarimetric sensors can be made temperature insensitive but to
measure strain they require means for setting a zero strain reference. Composite structures are made from two or more
constituent materials with significantly different physical or chemical properties and they remain separate and distinct in
a macroscopic level within the finished structure. This feature allows for the introduction of an optical fiber sensors
matrix into the composite material. In this paper we present experimental evidence that the interactions between the
composite material and optical fibers during manufacturing process are very significant. The lamination process can
dramatically change the strain sensitivity of the highly birefringent (HB) fibers.
Numerical modelling of imaging fibre bundles and their application in optical coherence tomography
Show abstract
Imaging fibre bundles are widely used in image transmission systems in the visible spectral range1. Their image
transmission capabilities and flexibility make them interesting for OCT endoscopy2. However, cross-talk occurring
between individual fibres and multimode transmission cause deterioration of the images obtained with OCT systems.
In this study, a model of light propagation in a fibre bundle is developed using the Finite Difference - Time Domain
(FDTD) method in order to quantify these effects. The simulated bundle output power density distribution is
compared to experimental images.
A dynamic fiber optic strain and power change sensor
Show abstract
A dynamic and quasi-distributed sensor principle for simultaneous measurement of length changes and optical power
changes between reflection points in an optical fiber is presented. The technique is based on the incoherent optical
frequency domain reflectometry (I-OFDR). Length change resolutions < 1 μm and measurement repetition rates up to 2
kHz can be achieved using standard single-mode and multi-mode optical fibers. Simultaneous length change and
refractive index measurement as well as field test results showing the deformation of a masonry building under seismic
load are presented. Promising fields of application for this technique are the structural health monitoring sector and
chemical process control.
Highly sensitive fiber optic inclinometer: easy to transport and easy to install
Show abstract
We present the status of our work on a tube shaped 3D deformation sensor based on continuously distributed fiber
optic sensing. A sensor tube of very large diameter is used to ensure high sensitivity while the transportability
and applicability are still comfortable due to our application strategy. The setup is designed to use different
measurement techniques in the applied optical fibers including Brillouin based measurements and interferometric
optical frequency domain measurements using an OBR 4400 from Luna Technologies.
Linear-core-array optical fiber based laser beam shape convertor
Show abstract
Based on the specialty designed linear-core-array fiber, a laser beam shape convertor has been
proposed and demonstrated. The experimental and theoretical results shown that a multi beam with the peak
power distributed in a linear array have been obtained at the end of the linear-core-array fiber and the output
beam shape depend on the coupling condition and the supermodes propagation distance along the
linear-core-array fiber. This device transfers the laser shape from a Gaussian beam to a controlled linear array
beam. It could be used in industry for manufacturing or medicine applications.
Launching the excitation light to a taper externally: comprehensive performance improvement of fiber-optic evanescent-wave sensor
Show abstract
A taper at one end of the fiber serving as the sensing element is widely used to enhance the performance of evanescentwave
(EW) fiber-optic sensors. However, almost all sensors of this type launch the excitation light into the core at the
opposite end and the entire taper has to be immersed into the bulky sample volume. This paper introduces a new way of
injecting excitation light: from the outside of the taper perpendicularly. As a result, several desirable features are
achieved simultaneously, including a dramatic increase of collectable EW signal, elimination of stray excitation light,
easy system construction and reduction of the sample volume to mere microliters.
An improved radiometric wavelength measurement system incorporating fibre comb filters fabricated by CO2 laser irradiation
Show abstract
An improved ratiometric wavelength measurement system incorporating two fibre comb filters is presented, which
performs both rough and fine wavelength measurements simultaneously. The resolution of the system is significantly
improved, compared to a single edge filter system, to better than 5 pm while maintaining the potential for high
measurement speed and wide measurable wavelength range.
Turbidity sensor for determination of concentration, ash presence and particle diameter of sediment suspensions
Show abstract
The present work addresses the need for low-cost turbidity sensors felt in the context of an ongoing research project on
enhanced soil erosion following wildfire in Portugal. To this end, a system based on plastic optical fibre was developed
and tested, including against a commercially-available system. The performance of the sensor was tested using
artificially-created samples with a wide range of concentration of three types of very distinct materials, six particle size
classes of ashes and real runoff samples collected at the slope and catchment scale in a recently burned area.
Fiber ringdown breathing rate sensor
Show abstract
We describe a new sensor for patient's breathing measurement by using fiber loop ringdown spectroscopy. The sensing
system consists of a typical single mode fiber-loop ring-down spectroscopy and a sensor mat which is used to introduce
breathing related optical loss. The sensor mat could be put in the chair or embedded in the bed. It is non invasive
measurement. The breathing rate sensor is demonstrated with an accuracy of +/-2 breaths per minute and stable sensor
output.
Optical fiber ferrule-top sensor for humidity measurements
Grzegorz Gruca,
Jan Rector,
Kier Heeck,
et al.
Show abstract
We present an optical fiber ferrule-top sensor for humidity measurements. Changes in water content in a gaseous
environment are detected by monitoring the resonant frequency and the quality factor of a cantilever fabricated on top of
a ferruled optical fiber. Our experimental data demonstrate that the device offers high resolution and high repeatability.
Micro fluidic channel actuator using optical force induced by evanescent field material coupling
Show abstract
A hollow optical fiber (HOF) has an unique modal distribution of a central evanescent field due to its structure.
The HOF consists of a central air hole, a Ge-doped ring core placed at the inmost layer, and silica cladding,
which induces the weak evanescent field at the central hole. By the structure with geometric symmetry, it is
possible to inject a refractive fluid into the hole and to modify the modal distribution. When a refractive index of
the fluid is same with or higher than the core's, guiding of light becomes dominant at the center and the ringshaped
field turns into a LP01 mode. During the process, optical force is induced and the net momentum of the
fluid is changed. The direction of optical force is opposite to that of light propagation, and the fluid come to be
dragged along the central channel in the HOF. In order to further investigate the phenomenon, we have changed
the refractive index of the fluid and measured resultant optical force. The direction and strength of the optical
force was dependent on the refractive index of the central fluid, which shows ample potential of the HOF as a
refractive index sensor.
Hydrazine concentration fiber optic reversible sensor
Show abstract
This paper reports the development of a reversible fiber optic leak sensor capable of detecting the presence and the
concentration of traces of hydrazine. The sensor operates in the lowest attenuation wavelength range of commercial
silica fibers. The sensing material utilized in this sensor is a mix of organic compounds that contains
pentacenediquinone (PDQ) as an active sensing element. The index of refraction of this mix is adjusted to closely match
that of fiber's silica core. In the absence of hydrazine this mix exhibits a weak absorption in the near-infrared. When the
PDQ reacts with hydrazine, oxygen atoms from the PDQ are replaced by a molecule of hydrazine resulting in water as a
by-product. This replacement significantly increases the absorption of the mix specifically at wavelength between 1310
and 1430 nm. This absorption was found to be proportional to hydrazine gas concentration. The reaction however is a
self-reversible i.e. in the presence of water; the by-products of the reverse reaction would be PDQ and hydrazine.
A modified cladding fiber sensor was fabricated by replacing part of cladding with the PDQ sensing mix. Due to
evanescence-wave absorption by the modified sensing cladding, the optical signal passing through this sensor exhibited
a reversible intensity change in the presence hydrazine at different concentrations. Sensor's percentage response
magnitude and response time were found to be proportional to HZ gas concentration. Hence, in addition to low loss
operating wavelength advantage, this sensor is capable not only to detect HZ presence of but also its concentration.
Composite cavity fiber laser sensor based on feedback modulation
Show abstract
We proposed a novel intensity modulation based composite cavity optical fiber laser (CCFL) sensor, which is
suitable for the vibration measurement. The intensity modulation of the CCFL is caused by the modulation of the
weak feedback of the CCFL. The weak feedback of the CCFL is based on the end face reflection and the Rayleigh
scattering of optical fiber. An acoustic measurement of the CCFL sensor in anechoic water pool is demonstrated to
prove that the simple sensing scheme is feasible.
Highly sensitive refractive index sensor based on cladding mode interference in microtapered SMF
Show abstract
A novel, highly sensitive refractive index sensor based on the modal interference in a microtapered telecom grade SMF
is presented. The considered structure consists of a uniformly thinned region in between the tapered regions where the
original core is virtually absent and the modes are supported by the cladding-ambient region index difference. The core
mode evolution within the tapered region and its coupling to the cladding modes has been obtained using the localnormal-
mode-matching. The proposed device has extremely high sensitivity ~ 2.6 μm/RIU for biological samples (nse ~
1.33) and hence should be useful for precision bio/chemical sensing applications.
Structural bending sensor with temperature insensitivity based on a single polarization fiber
Show abstract
We propose the temperature-insensitive bending sensor based on a hole-assisted single polarization fiber (SPF). Without
fiber grating structures, the SPF-based sensing probe can provide the sensing technique to measure the bending change.
If bending is applied to the SPF, two cutoff wavelengths are shifted to shorter wavelengths and the transmission power is
diminished because the structural deformation of the SPF induced by bending changes birefringence depending on
principle axes of the SPF. However, the applied temperature variation has no effect on the birefringence change severely
and two cutoff wavelengths are not shifted by changing temperature. Therefore, the proposed SPF-based sensing probe
with temperature insensitivity can measure the bending change effectively.
High-speed focusing of a liquid microlens using acoustic radiation force
Show abstract
A compact, high-speed variable-focus liquid lens using acoustic radiation force is proposed. The lens consists of an annular
piezoelectric ultrasound transducer and an aluminum cell (height: 3 mm; diameter: 6 mm) filled with degassed water and
silicone oil. The profile of the oil-water interface can be rapidly varied by applying acoustic radiation force from the
transducer, allowing the liquid lens to be operated as a variable-focus lens. A theoretical model based on a spring-mass-dashpot
model is proposed for the vibration of the lens. The fastest response time of 6.7 ms was obtained with silicone oil
with a kinematic viscosity of 100 cSt.
Refractive index measurement by using multimode interference
Show abstract
A fiber-optic refractometer based on the multimode interference in the singlemode-multimode-singlemode
fiber structure is demonstrated. The refractive index dependence of the shift of re-imaging resonant wavelength of the
proposed sensor is investigated. It shows that the proposed sensor has a measurement resolution of 5.4×10-5 refractive
index unit (RIU) for the changes of refractive indices from 1.336 to 1.372. The proposed sensor has a great potential for
biological and chemical applications.
The use of a bent singlemode-multimode-singlemode (SMS) fiber structure for vibration sensing
Show abstract
A bent singlemode-multimode-singlemode (SMS) fiber structure based vibration sensor is proposed and developed.
This sensor configuration is very simple and employs a bent SMS fiber structure and a narrow band optical source such
as a laser. The vibration applied to the bent SMS fiber structure will change the bend radius and hence the intensity of the
transmitted optical power will also vary. Experimental results show that the sensor can detect vibration frequencies over
a broad range with good sensitivity, from hertz to a few kHz.
Investigation of single mode polarization-maintaining fibres for directional transverse force measurement
Show abstract
Direct measurement of transverse force has been investigated in this work by using two specialist single mode
Polarisation-Maintaining (PM) side-hole(s) fibres. Variations in the pressure sensitivity of side-hole fibres with different
rotation angles and magnitudes of the applied external force have been investigated both theoretically and experimentally
and it was confirmed that they are dependent upon the force direction, with reference to the fast or slow axis of the
fibres. The experimental results obtained have shown good agreement with theoretical predictions when appropriate
cross-comparisons were made. Thus these fibres have shown potential to be used as optical fibre sensors for the
measurement of pressure, force and mass of an object, applied in different directions, over a wide range and in real time.
Measurement of sucrose and ethanol concentrations in process streams and effluents of sugarcane bioethanol industry by optical fiber sensor
Show abstract
The measurement of process streams and effluents from sugar-ethanol industry by using optical fiber sensor based on
Fresnel reflection principle is reported. Firstly, binary sucrose-water and ethanol-water solutions were measured in order
to determine the calibration curves. Secondly, the co-products from various processing stages were analyzed in order to
identify the sucrose or ethanol concentration. The absolute error was calculated by comparison between the nominal
concentration values obtained by plant laboratory analysis and the sensor response, yielding errors ≤ 5 wt% and ≤ 5 vol%
for sucrose and ethanol content, respectively. The fiber sensor provided reliable results even for samples with more
complex compositions than pure sucrose or ethanol solutions, with perspectives of application on the several stages of
the plant facility.
Ultra fast all-optical fiber pressure sensor for blast event evaluation
Show abstract
Traumatic brain injury (TBI) is a great potential threat to soldiers who are exposed to explosions or athletes who receive
cranial impacts. Protecting people from TBI has recently attracted a significant amount of attention due to recent military
operations in the Middle East. Recording pressure transient data in a blast event is very critical to the understanding of the
effects of blast events on TBI. However, due to the fast change of the pressure during blast events, very few sensors have
the capability to effectively track the dynamic pressure transients. This paper reports an ultra fast, miniature and all-optical
fiber pressure sensor which could be mounted at different locations of a helmet to measure the fast changing pressure
simultaneously. The sensor is based on Fabry-Perot (FP) principle. The end face of the fiber is wet etched. A well
controlled thickness silicon dioxide diaphragm is thermal bonded on the end face to form an FP cavity. A shock tube test
was conducted at Natick Soldier Research Development and Engineering Center, where the sensors were mounted in a
shock tube side by side with a reference sensor to measure the rapidly changing pressure. The results of the test
demonstrated that the sensor developed had an improved rise time (shorter than 0.4 μs) when compared to a commercially
available reference sensor.
Fibre optic pressure sensor system for high temperature exhaust gas flows
Show abstract
Sensing the pressure of gasses in the exhaust manifold of an internal combustion engine is a challenging application. The
exhaust gasses themselves are rapidly changing with temperatures involved that can be in the region of 800°C. This
paper presents a Fibre Optic Pressure Sensor (FOPS) system designed specifically for this application. The FOPS system
consists of an Extrinsic Fabry Perot Interferometer / Fibre Bragg Grating hybrid sensor, which is able to measure
pressure and temperature simultaneously at the point of measurement, and a feedback controlled single wavelength
interrogation technique. The combination of both allows the acquisition of fast pressure fluctuations in high temperature
environments.
Design of a polarization-insensitive optical fiber probe based on effective parameters
Show abstract
By inserting a polarization controller, a polarization-insensitive optical fiber probe is first proposed. In order to
design a fiber probe acting as a free-space media, the five effective parameters of an optical fiber are extracted by an
analytical technique based on the Mueller matrix and the Stokes parameters. The feasibility of the common-path
interferometer with a polarization-insensitive optical fiber probe for remote measurements is demonstrated by absolutely
extracting the linear birefringence and linear diattenuation properties of a quarter-wave plate and a polarizer, respectively.
A polarization-insensitive fiber probe is crucial for optical fiber applications in a polarization-sensitive near-field
scanning optical microscopy and the remote sensing.
Enabling low-cost, high-performance vapor-phase TNT detection by optimizing multimode fiber sensing platform
Show abstract
Identification of trace-vapor TNT explosive emanating from mines or IEDs is in urgent demand due to today's mounting
terrorist threat. Amplifying fluorescent polymer (AFP) based on quenching offers an opportunity for progress in this
regard. Maximizing the performance of this material and meeting the requirements of real-life situations, however, pose
challenges to the sensing platform design. We address these challenges by establishing a multimode fiber-optic sensing
platform with a millimeter-scale sensing element and our alternative TNT sensory polymer to AFP. Theoretical
calculation is given, demonstrating the highly efficient use of the excitation power, which allows for the sensing head to
be as miniature as 0.8×0.8×1.6 mm. The exposure of our sensor to the TNT vapor gives a fast response, at the level of
30% power quenching occurring within 10 seconds. Another major advantage of our solution is that the mechanism of
stray excitation light is eliminated naturally due to the design of the platform architecture.
Remote ice detection system for on-board applications based on fiber optics
Show abstract
In this paper we describe a fiber-based remote sensing device for the detection of liquid water and ice on the road surface
suitable for on-board applications. The system is based on the different optical responses of water and ice to three near
infrared wavelengths from low-cost semiconductor laser sources. The design of the sensor is divided in three main parts:
The optical fiber-based illumination and collection optics, the optoelectronic system composed by the emitters/detector
and the modulation/demodulation electronics and, finally, the data acquisition and digital processing system. The flexible
optical design allows both the use of the sensor attached to a post by the road for static measurements, or to be
incorporated into a road maintenance vehicle.
Fiber-optic rotational seismic system for investigation of the rotational events
Show abstract
The paper presents a new telemetric system for direct measurement and investigation the rotational components exist in
seismic events. The FORS - fiber optic rotational seismometer and seismographs constructed on the base of the Sagnac
interferometer are the elements of the system. The special construction of the system protects their elements remote
control in real time via internet utilize the GSP/GSM connections. The first results according application autonomous
FORS (AFORS) with accuracy in the range 4.9·10-9 - 6.1·10-8 rad/s in detection bandpass 1.66 - 212.30 Hz located in
Ksiαz and Warsaw, as well as older one FORS-II (mounted in Ojców) are reported.
Three-component all polarization-maintaining optical fiber vector hydrophone
Show abstract
This paper reports a new-style all polarization maintaining optical fiber vector hydrophone which is orthogonal and
unitized in three components. The signal fading caused by random phase-shift in the interferometer is eliminated by
phase generated carrier (PGC) technology. The sensitivity and frequency band of the sensor is increased by optimizing
the structure. Experimental results indicate that the acceleration sensitivity reaches 33dB and the fluctuation is less than
1dB over the frequency range of 20~2000Hz. The phase sensitivity is -155dB at 1000Hz. The optical vector hydrophone
has an excellent directivity. The maximum asymmetric index is less than 0.4dB, while the directivity index is greater
than 45dB.
Improving optical fiber current sensor accuracy using artificial neural networks to compensate temperature and minor non-ideal effects
Antonio C Zimmermann,
Marcio Besen,
Leonardo S. Encinas,
et al.
Show abstract
This article presents a practical signal processing methodology, based on Artificial Neural Networks - ANN, to process
the measurement signals of typical Fiber Optic Current Sensors - FOCS, achieving higher accuracy from temperature
and non-linearity compensation. The proposed idea resolve FOCS primary problems, mainly when it is difficult to
determine all errors sources present in the physical phenomenon or the measurement equation becomes too nonlinear to
be applied in a wide measurement range. The great benefit of ANN is to get a transfer function for the measurement
system taking in account all unknowns, even those from unwanted and unknowing effects, providing a compensated
output after the ANN training session. Then, the ANN training is treated like a black box, based on experimental data,
where the transfer function of the measurement system, its unknowns and non-idealities are processed and compensated
at once, given a fast and robust alternative to the FOCS theoretical method. A real FOCS system was built and the
signals acquired from the photo-detectors are processed by the Faraday's Laws formulas and the ANN method, giving
measurement results for both signal processing strategies. The coil temperature measurements are also included in the
ANN signal processing. To compare these results, a current measuring instrument standard is used together with a
metrological calibration procedure. Preliminary results from a variable temperature experiment shows the higher
accuracy, better them 0.2% of maximum error, of the ANN methodology, resulting in a quick and robust method to
hands with FOCS difficulties on of non-idealities compensation.
Long-gauge strain sensors for underwater and deep-water applications
Show abstract
The evaluation of the structural performance of marine structures, such as ship hulls, off-shore platforms and risers
requires the monitoring of the static and dynamic strain levels undergone during the whole lifetime. In these
environments, the use of passive fiber optic sensors presents advantages in terms of reliability and multiplexing ability.
Frequently used structural materials, such as steel and composites, exhibit local defects or discontinuities, such as welds,
thickness / diameter variations, marine growths and cracks, introducing discontinuities in the mechanical properties of
the material at a local level. Yet, the properties of the material at a global level are more indicative for structural
behavior. Therefore, for structural monitoring purposes, it is necessary to use sensors that are insensitive to local
material discontinuities. A long-gauge strain or deformation sensor, by definition, is a sensor with a gauge-length several
times larger than the maximal distance between discontinuities or the maximal diameter of defects in the monitored
material. In this paper we will present the design, testing and applications of a long-gauge fiber optics strain sensor for
underwater applications.
Characterization of tapered polymer optical fibers under side illumination for fluorescence sensing applications
C. Pulido,
Ó. Esteban
Show abstract
In this work we present the fabrication and characterization of tapered polymer fibers used as fluorescence based sensors
with a side-illumination arrangement. The fabrication method consists of a travelling-heater that gives a tight control of
the tapered fibers parameters, namely the taper waist and the profile of the transition length between the unaltered fiber
and the taper waist. Furthermore, a different approach for using fluorophores in fluorescence based sensors has been
developed. With our method, we can locally introduce a fluorescent dye inside the taper region, which could lead to the
generation of cuasi-distributed sensors for lengths of hundred of meters.
Optical characterisation of RF sputter coated palladium thin films for hydrogen sensing
Show abstract
We investigate the optical properties of Pd thin films of the thickness 20-100nm deposited on Si wafer via RF sputter
coating. The Pd samples are characterised using white light interfermometry for thickness and ellipsometry for
refractive index. We demonstrate the independence of refractive index on film thickness above 20nm. Considerable
discrepancy is found between our measurement and previously published complex refractive indices for both bulk and
RF sputter coated Pd, indicating a high degree of dependence on deposition technique.
Design and optimization of an optical refractometer for remote measurements via fiber-optic cables
S. Khotiaintsev,
C. E. García-Guerra,
J. E. Morales-Farah,
et al.
Show abstract
This paper presents a fiber-optic refractometer which can operate via long fiber-optic cables. We address the relationship
between the span and the linearity of the small micro-optical evanescent-field transducer with spherical working surface
used in the sensor, under different parameter combinations. We designed the transducer for the range of 1.333<n<1.358,
which is of main practical interest in measurements of water salinity. Another version of virtually the same transducer
was designed for the range of 1.333<n<1.380, which corresponds to concentrations of sodium chloride in water from
zero to saturation. We also addressed the effect of the unstable optical source and loss in the connecting fiber-optic
cables, on the readings of the refractometer. We significantly reduced these negative effects by implementing the
refractometer in an optical bridge configuration followed by an analogue optoelectronic signal processing unit. This
made the refractometer almost insensitive to the parasitic variation of optical source and loss in the fiber-optic cables
which connects the optical probe with the optoelectronic unit. Due to these measures, this refractometer can successfully
operate via long fiber-optic cables. It can have applications such as in the food industry, where salt-brine solutions of
various concentrations are widely used.
Stripping and splicing polyimide-coated fibers
Douglas Duke,
Yoshiharu Kanda,
Kenyo Tobita,
et al.
Show abstract
Polyimide is often used as a coating material for optical fibers used in high temperature environments such as aerospace
or oil and gas sensor applications. Unfortunately, polyimide coating is very difficult to strip by conventional mechanical
stripping methods. The glass fiber is easily damaged if the stripping process is not extremely well controlled. Stripping
the polyimide coating by heating with a flame or arc typically results in a significant reduction in fiber strength. Strength
may be maintained by using hot acid stripping, however the use of the strong hot acid presents safety hazards and also
requires controlled and safe waste disposal. Another issue with polyimide coating is variability of the coating diameter
from various manufacturers or due to different polyimide coating processes. This not only complicates the polyimide
stripping issue, but also presents problems with precise clamping and alignment during splicing, especially when it is
necessary to splice with a short cleave length.
In this paper, we present new polyimide coating stripping technology. The significant feature of this stripping technology
is achievement of good strength while avoiding the use of hot acid or heating. We also developed a new specialty fiber
fusion splicer that enables precise alignment and splicing regardless of the variability of polyimide coating diameter,
even when clamping on the coating.
Mode field analysis of eccentric optical fibers by conformal mapping
Show abstract
The mode field characteristics of eccentric optical fibers are investigated theoretically. The eccentric optical fiber is
converted to be a concentric three-layered optical fiber through the conformal representation and the corresponding field
distribution is given by solving eigenvalue equation of a general three-layered optical fiber waveguide. The method
should be proved a simple solution for optimizing the configurations of special optical fibers.
Twin-half hollow elliptical core polarization-maintaining fiber for polarization state selective sensing
Show abstract
We propose and fabricate a twin-half hollow elliptical core polarization maintaining fiber. The shape of the core in the
polarization maintaining fiber is designed to be elliptical for generating a geometry birefringence. In the cladding, two
half-hollows are symmetrically distributed with respect to the elliptical core for producing a stress birefringence.
Therefore, the birefringence in such a polarization maintaining fiber is the mixed effect of the geometry and stress
birefringence. The birefringence generating mechanism is analyzed in detail and a theoretical formula depicting the
birefringence is built up. The simulation results for the twin-half hollow elliptical core fiber at different structural
parameters are obtained by using finite element method. Through adjusting the structural parameters of the fiber, the
relationships between the birefringence and the core diameter as well as the width of the core bridge are discussed.
A compact fiber optic accelerator
Show abstract
A compact fiber optic Michelson interferometer based accelerometer is proposed and demonstrated. In this sensing
system, two optical fibers have been used as the differential sensing element. By way of demodulating the different
optical phase, we can obtain the acceleration which proportional to the initial force applied on the central position
of the two fibers. A simple model has been built to calculate the sensitivity and resonant frequency. The
experimental results show that such an accelerometer has a sensitivity of 0.42rad/g at the resonant frequency
600Hz.
In-fiber integrated accelerator
Show abstract
A compact in-fiber integrated fiber-optic Michelson interferometer based accelerometer is proposed and investigated. In
this sensing system, the sensing element consists of a twin-core fiber acting as a bending simple supported beam. By
way of demodulating the optical phase shift, we can obtain the acceleration which proportional to the initial force
applied on the central position of the twin-core fiber. A simple model has been established to calculate the sensitivity and
resonant frequency. The experimental results show that such an accelerometer has a sensitivity of 0.09rad/g at the
resonant frequency of 700Hz.
Optical path correlator for low-coherence multiplexing fiber optic sensor
Show abstract
Based on a cavity length tunable fiber loop resonator, a multi-beam optical path difference is generated. It can
be used to match and correlate the reflective signals from the partial reflective ends of each sensing fiber
gauge. The correlation signals corresponding to the sensing gauge lengths. And the shift of the correlation
peak related with the fiber sensing gauge elongation caused by strain or temperature. Therefore, it can be used
to measure distributed strain or deformation for smart structural monitoring.
Highly sensitive optical fiber oxygen sensor based on dye entrapped core-shell silica nanoparticles
Show abstract
This paper presents a highly-sensitive oxygen sensor that comprises an optical fiber coated at one end with platinum
(II) meso-tetrakis (pentrafluorophenyl)porphine (PtTFPP) and PtTFPP entrapped core-shell silica nanaparticles
embedded in an n-octyltriethoxysilane (Octyl-triEOS)/tetraethylorthosilane (TEOS) composite xerogel. The sensitivity of
the optical oxygen sensor is quantified in terms of the ratio I0/I100, where I0 and I100 represent the detected fluorescence
intensities in pure nitrogen and pure oxygen environments, respectively. The experimental results reveal that the oxygen
sensor has a sensitivity of 166. The response time was 1.3 s when switching from pure nitrogen to pure oxygen, and 18.6
s when switching in the reverse direction.
Characteristics of hydrogen gas sensor based on a wavelength division multiplexing fiber coupler
Show abstract
A fiber optic sensor based on the wavelength division multiplexer coated with a palladium (Pd) thin film is designed for
hydrogen gas detection. The sensing mechanism of this sensor is measuring the wavelength shift that is induced by the
evanescent field interaction with the refractive index change of Pd film when it absorbs hydrogen.
Fiber optic sensors for monitoring a concrete beam high strain bending test
M. Bravo,
J. Sáenz,
M. Bravo-Navas,
et al.
Show abstract
In this work the development of "eight-shape" fiberoptic sensors for high strain sensing applications is shown. A
concrete beam bending test has been performed to compare a FBG with our low-cost intensity bending sensor when
used for high strain monitoring.
Radiation-resistance technology for broadband fiber-optic source
Show abstract
The effect of gamma ray radiation on the performance of a compact Er-doped super-fluorescent fiber source was
investigated experimentally. It was found that the output power and spectrum of the source vary significantly with
radiation dosage and probably the induced background loss for the pump would play a significant role in the observed
variations. A double-pass backward source configuration with an output edge filter was implemented experimentally, and
with proper feedback control pump driving circuitry, such a configuration demonstrated good resistance to gamma ray
radiation.
Construction optimization of the sensors used in point fluorescence investigation of cancer-changed tissues
Show abstract
Fluorescence is a known phenomenon used in different fields of research. For the purpose of this study, different types
of fiber optic sensors were used to investigate cancerous tissues with one photon fluorescence. Several probes were
tested in terms of their sensitivity and efficiency of resulting measurements. The obtained fluorescence spectral
characteristics, with intensity peaks typically falling in 480-520nm range, outlined clearly pathologically changed areas.
The intensity of detected fluorescence determines the evaluation of disease advancement.
CO[sub]2[/sub] phase study using an optical fiber refractometer
Show abstract
A refractive index sensor based on the Fresnel reflection at the tip of a single mode optical fiber is used to study phase
changes of CO2 when cooled down from room to -50° C. The sensor system is compact and can be readily integrated into
other optical and electronic systems. The refractive index measurements present good agreement with the literature. The
use of the refractometer as a tool to determine the CO2 phase in oil fields is envisaged.
Low loss arc splicing of silica microfibers
Show abstract
We demonstrated the splicing of 2 μm diameter microfibers by using a modified arc discharge device. Two microfibers
were aligned with the help of van der Waals forces before fusing them together by arc discharging. Most splicing losses
were below 1 dB, and the lowest was 0.16 dB. A spliced microfiber did not induce undesired wavelength selection
because arc splicing was a complete joining technique which is different from evanescent coupling. Simulation results
show splicing coupling has better averaged coupling efficiencies than evanescent one over various overlapping lengths,
and the measured results show consistency.
Performance characterization of an intensity-modulated fiber optic displacement sensor
Show abstract
A testbed simulating an intensity-modulated fiber optic displacement sensor is experimentally characterized, and the
implications regarding sensor design are discussed. Of interest are the intensity distribution of the transmitted optical
signal and the relationships between sensor architecture and performance. Particularly, an intensity-modulated sensor's
sensitivity, linearity, displacement range, and resolution are functions of the relative positioning of its transmitting and
receiving fibers. In this paper, sensor architectures with various combinations of these performance metrics are
discussed. A sensor capable of micrometer resolution is reported, and it is concluded that this work could lead to an
improved methodology for sensor design. This paper has been approved by Los Alamos National Laboratory for
unlimited public distribution (LA-UR 10-06637).
Fiber optic hydrogen sensor resisting temperature interference
Show abstract
The principle of an extrinsic Fabry-Perot interferometric (EFPI) optical fiber hydrogen sensor is introduced in the paper.
In order to carry out the mathematic model of the relationship between the change of Fabry-Perot gap length and
hydrogen concentration, the stress transfer model of the sensor is analyzed. Two channels temperature compensation
method is used to avoid the interference caused by the variation of the environmental temperature, so the stability of the
system is enhanced. The validity of theory has been proved by means of investigating the responsibility of the sensor in a
function of the hydrogen concentration, and the analytic data was close to the experiment results.The feasibility of the
sensor has been validated by the temperature experiment.
Light scattering measurements for quantifying biological cell concentration: an optimization of opto-geometric parameters
Show abstract
An experimental study was carried out, aimed at optimizing the optical/geometrical configuration for measuring the
concentration of biological cells by means of static light scattering measurements. A LED-based optoelectronic setup
making use of optical fibers was experimented, as the precursor of a low-cost device to be integrated in instrumentation
for cytometry. Two biological sample types were considered as test samples of the most popular analyses - cervical
cells and urine, respectively. The most suitable wavelengths and detecting angles were identified, and calibration curves
were calculated.
High pressure measurement by nonadiabatic tapered optical fiber sensor for downhole application
Show abstract
We report fabrication of a high pressure nonadiabatic tapered optical fiber (NATOF) for downhole applications by using a
mechanical transducer. The mechanical transducer has been used for increasing the pressure sensitivity and possibility of
installation the sensor in downhole. The NATOF is fabricated by heat pulling method, utilizing a CO2 laser. The limit of
detection of the NATOF was 15 psi.
Nonadiabatic tapered optical fiber sensor for measuring interaction nicotine with DNA
Show abstract
A nonadiabatic tapered optical fiber sensor was utilized for studying of bimolecular interactions including DNA-DNA
and DNA-Drug interaction. This work presents a simple evanescent wave sensing system based on an interferometric
approach, suitable to meet the requirements of lable-free sensor systems for detecting biomolecular interactions. We have
demonstrated the measuring refractive index and the real time detection of interactions between biomolecules.
Furthermore basic experiments were carried out, for detecting the hybridization of 25-mer DNA with an immobilized
counterpart on the surface. The overall shift after the successful DNA hybridization was 9.5 nm. In this work, a new
approach for studying DNA-drug interactions was successfully tested. Nicotine as a carcinogenic compound in cigarette
smoke plays an important role in interaction with DNA. Different concentrations of nicotine were applied to observe the
Longmuir interaction with DNA.
Spectral intensities and phase distributions of supercontinuum pulses generated in low-dispersion fibers
H. Sone,
D. Yoshitomi,
X. Zhou,
et al.
Show abstract
It was reported recently that optical pulses propagating through a tapered fiber (TF) immersed in heavy water (D2O) or
photonic crystal fiber (PCF) of special design yield a broad and flat supercontinuum (SC) spectrum because the fiber
dispersion characteristics are of low dispersion: around 1000 nm. This work was undertaken to investigate spectral
intensities and phase distributions of SC pulses generated in low-dispersion fibers. Results show that PCF with group
velocity dispersion (GVD) distributions having an extremum value of zero dispersion can be used at short fiber length
for applications where the phase distribution is a concern.
Optical fibers and sensors for biomedical applications: bend effects
Show abstract
Optical fibers are finding increased usage in biomedical applications, during which the fibers are often subjected to
bending. Bending optical fibers can affect transmission properties and increase the likelihood of failure. In this paper the
bending of fibers is discussed in relation to biomedical and sensing applications.
Measurement of the velocities in the transient acceleration process using all-fiber photonic Doppler velocimetry
Show abstract
Based on analysis of basic photonic Doppler velocimetry (PDV), a formula to measure velocity variation in a single
cycle is put forward. PDV has been improved in three aspects, namely, the laser, the detector and the data processing. A
measurement system for velocity of the initial stage of a shock motion has been demonstrated. Instantaneous velocity
measurements have been performed. The experimental results have a good agreement with the values obtained from the
accelerometer. Compared with the traditional fringe method, the proposed method in this paper can identify
instantaneous velocity variation. So it is particularly suitable for measuring the velocity in the transient acceleration
process of shock waves and detonation waves.
Two-beam fiber laser Doppler velocimeter enabling velocity distribution measurement of liquid flow
Show abstract
By using 2-beam fiber laser Doppler velocimeter (LDV), velocity measurement can be conducted by using the offset angle between laser beams. Another unique feature in velocity measurement using 2-beam LDV is the appearance of the third spectrum that can be observed when 2 laser beams irradiate to the same spot on the measurement target. We demonstrated the application of third spectrum frequency to obtain moving object velocity within velocity distribution of liquid flow.
Induction heating assisted optical fiber bonding and sealing technique
Pawel Niewczas,
Grzegorz Fusiek
Show abstract
A novel technique for providing hermetic sealing within an optical fiber feed-through or high-performance fiber
attachment to a metal part is presented. The system utilizes a specially designed heat concentrator surrounding the metal
part and metal coated fiber that is heated to above 800°C using an induction heating method to achieve melting of a hightemperature
brazing material used to join the two parts. The strength of the bond and sealing between the fiber and metal
part is evaluated by constructing a simple extrinsic Fabry-Perot pressure transducer subjected to temperature and
pressure variations in the range of 20-350°C and 0-15,000 psi, demonstrating the expected spectral responses from the
transducer.
PCF Sensors
DNA probe detection within 3D hydrogel matrix in a hollow core photonic crystal fibre
Show abstract
In this paper, we report for the first time the detection of a Cy5-labelled DNA probe immobilised within a 3D hydrogel
matrix formed, inside a hollow core Photonic Crystal Fibre (HC-PCF). We show both the sensitivity of fluorescence
detection inside the HC-PCF using a supercontinuum light source and of the variation of the luminescence intensity with
the concentration DNA probe within the hydrogel. The 3D hydrogel matrix is a network of polymer chains, which is
expected to provide highly sensitive detection and selection of bio-molecules, in comparison with 2D coverage. The
biocompatibility of hydrogel in the HC-PCF suggests numerous applications associated with immobilised DNA probe
detection for point-of-care or remote systems.
Introduction of birefringence into photonic crystal fibers
Show abstract
Selective opening and closing of air-holes in photonic crystal fibers (PCFs) are realized by using a femtosecond infrared
laser and a CO2 laser. By heating/tapering the PCFs while pressurizing those opened holes, the birefringent properties of
the PCFs can be modified. High birefringence of 3.6×10-4 and 1.5×10-3 were obtained by post-processing commercial
LMA-10 and HC-1550-02 fibers.
High performance interrogation of long period fiber grating sensor with wavelength scanning and Fourier analysis
Show abstract
A long-period fiber grating (LPG) sensor is interrogated with the wavelength-to-time mapping scheme. Highspeed
scanning of the laser light source wavelength generates a train of optical dark pulses in the transmitted
light through the LPG whose peak position is modulated according to the wavelength change caused by the
environmental influence. The generated dark pulses are Fourier-analyzed and the information on the wavelength
shift is retrieved. The result in the temperature sensing shows the linearity of the sensor system and the validity
of the interrogation scheme is verified. The scheme can be also applied to the sensing of the dynamic influence.
With 20 kHz scanning frequency, dynamic influence of up to 10 kHz is expected to be interrogated. Utilizing
the characteristic advantage that a LPG can be tailored to be of higher or less sensitivity to the influence, the
proposed method can be expected to yield high performance operation of a LPG sensor.
Liquid crystal long-period fiber grating as a sensing element for electric field and temperature measurements
Show abstract
The main goal of the presented work is to integrate a long-period fiber grating (LPFG) and liquid crystal
(LC) material into a hybrid structure, called an LC-LPFG, in order to develop innovative devices for sensing physical
quantities. For this purpose we used specially designed low-birefringence LC mixtures whose ordinary refractive index
is lower than that of silica in a certain range of temperatures. This combination allowed us to dynamically change the
propagation properties of the cladding modes in the LC-LPFGs by varying the temperature and the electric field. This
design of LC-LPFGs exhibits extraordinary sensing properties.
FBG Sensors
Regenerated draw tower grating (DTG) temperature sensors
Show abstract
The idea of Bragg gratings, generated during the drawing process of a fiber dated back almost
20 years ago. The technical improvement of the DTG process results today in high reliable
and cost effective Bragg gratings for versatile application in the optical fiber sensor market.
Due to the single pulse exposure of the fiber, the gratings behave typically like type I gratings
with respect to their temperature stability. This means that such gratings only work up to
temperatures lower than 300 °C. To increase temperature stability we combined DTG arrays
with hydrogen loading and a thermal regeneration process which enables their use in high
temperature environment. The regenerated draw tower gratings are suitable for temperatures
up to 900°C.
Femtosecond laser inscribed Bragg sensor in Terfenol-D coated optical fibre with ablated microslot for the detection of static magnetic fields
Show abstract
A novel device for the detection and characterisation of static magnetic fields is presented. It consists of a femtosecond
laser inscribed fibre Bragg grating (FBG) that is incorporated into an optical fibre with a femtosecond laser micromachined
slot. The symmetry of the fibre is broken by the micro-slot, producing non-uniform strain across the fibre cross
section. The sensing region is coated with Terfenol-D making the device sensitive to static magnetic fields, whereas the
symmetry breaking results in a vectorial sensor for the detection of magnetic fields as low as 0.046 mT with a resolution
of ±0.3mT in transmission and ±0.7mT in reflection. The sensor output is directly wavelength encoded from the FBG
filtering, leading to simple demodulation through the monitoring of wavelength shifts that result as the fibre structure
changes shape in response to the external magnetic field. The use of a femtosecond laser to both inscribe the FBG and
micro-machine the slot in a single stage, prior to coating the device, significantly simplifies the sensor fabrication.
Transverse load sensing with a tilted fiber Bragg grating compressed between conforming elastomers
Show abstract
A novel fiber optic transverse load sensor is experimentally demonstrated by using a 10° tilted fiber Bragg grating
(TFBG) compressed between two conforming elastomer layers, which has a high refractive index and low Young's
modulus. The applied transverse loads increase the contact angle of optical fiber and conforming elastomers, which
suppress the cladding modes coupling and introduce a broadband loss in the spectrum of the TFBG. Using fast Fourier
transform (FFT) analysis on a selected bandwidth of the transmission spectrum, it is found that the peak amplitude of the
dominant spectral fringes decreases with the increasing transverse load with an near-linear sensitivity of 125 arbitrary
unit/N (in the range of 0~6N). Finally, the temperature effect on the response of sensor has been investigated at a
constant load of 3.8 N. The results show that the sensor is independent to temperature, with a maximum error of 2%
from 25 °C to 75 °C.
Experimental validation of a numerically determined multi-axial strain transfer from CFRP-laminates to embedded Bragg sensors
Show abstract
Embedded optical fibre sensors are considered in numerous applications for structural health monitoring purposes. Since
the optical fibre and the host material in which it is embedded, have different material properties, strain in both materials
will not be equal when external load is applied. In this paper, an experimental evaluation of the response of uni-axial
fibre Bragg grating sensors embedded in small cross-ply composite laminates subjected to out-of-plane transverse
loading is discussed.
Numerical modeling of complex femtosecond laser inscribed fiber gratings: comparison with experiment
Show abstract
We present experimental studies and numerical modeling based on a combination of the Bidirectional Beam Propagation
Method and Finite Element Modeling that completely describes the wavelength spectra of point by point femtosecond
laser inscribed fiber Bragg gratings, showing excellent agreement with experiment. We have investigated the dependence
of different spectral parameters such as insertion loss, all dominant cladding and ghost modes and their shape relative to
the position of the fiber Bragg grating in the core of the fiber. Our model is validated by comparing model predictions
with experimental data and allows for predictive modeling of the gratings. We expand our analysis to more complicated
structures, where we introduce symmetry breaking; this highlights the importance of centered gratings and how
maintaining symmetry contributes to the overall spectral quality of the inscribed Bragg gratings. Finally, the numerical
modeling is applied to superstructure gratings and a comparison with experimental results reveals a capability for dealing
with complex grating structures that can be designed with particular wavelength characteristics.
Regenerated fibre Bragg gratings used to map internal reaction temperatures of a modified chemical vapour deposition (MCVD) optical fibre preform lathe
Show abstract
The temperature profile of the reaction zone inside the substrate tube of a modified chemical vapour deposition
(MCVD) optical fibre perform lathe has been characterised using thermal chirp compensated ultra-high
temperature stable regenerated optical fibre Bragg gratings (FBGs). Results indicate significant differences in
measured internal temperatures than those predicted theoretically or measured externally.
Multimode Effects
The use of fibre optic sensors to compare the internal strains and pressures produced by different Lamb wave modes
Show abstract
Lamb waves are a type of guided ultrasound wave that propagate in plate material and have found applications in the
fields of structural health monitoring and material properties evaluation. They have modal properties and are divided into
two categories, symmetric and antisymmetric. Normally they are measured through detection of surface movement;
however analysis shows that the greatest difference in particle motion between the modes is at the centre of the plate. In
this paper the use of fibre Bragg gratings and polarimeters, embedded at different locations within the plate, to detect the
differences in strain and pressure these ultrasound modes produce by is described.
Utilisation of thermal annealing to record multiplexed FBG sensors in multimode microstructured polymer optical fibre
Show abstract
Fibre Bragg gratings have been UV inscribed in multimode microstructured polymer optical fibre in both the 1550nm and
800nm spectral regions. Thermally annealing the fibre at 80°C has been shown to shrink the fibre length and as a result a
permanent negative Bragg wavelength shift is observed. The blue shift can be tuned between 0-16nm in the 1550nm spectral
region and 0-6nm in the 800nm spectral region, depending on the duration the heat is applied before a saturation level is
reached and the fibre stops shrinking in the region of 2 hours. Exploiting this, wavelength division multiplexed sensors have
been UV inscribed in both the 1550nm and 800nm regions using a single phase mask for each wavelength region. The
800nm sensor takes advantage of the lower attenuation of poly (methyl methacrylate) of 2dB/m compared to 100dB/m at
1550nm.
Target delivery to sensors by using generated uniform three fiber pseudo Bessel beams from one source
Show abstract
A new and flexible method to deliver target particle to sensor through optical trapping with pseudo Bessel
beam is presented. Pseudo Bessel beam generator was based upon a Fourier optical system. Single mode fiber
(SMF) delivered a fundamental mode without loss. SMF was spliced with Hollow optical fiber (HOF) which
served as an annular aperture. A light wave with ring shape was propagated in Coreless Silica Fiber (CSF) and
simultaneously transformed a Bessel shape. A Bessel shape with central peak profile will be maintained by a
tiny polymer lens on the end of CSF. Delicate control of particle position was enabled by 3 pseudo Bessel beam
sources which can be controlled individually. Unique characteristic of Bessel beam allows target particle to have
few hundred micrometer tolerance in propagation length and sudden change of propagating direction was
achieved by applying another Bessel beam source from other direction. Experimental results on Polystyrene
beads which have 4 um diameter are shown. Also, living cell such as Jurkat cell was tested to check practicality.
Development of a FBG vortex flow sensor for high-temperature applications
Show abstract
A robust fibre optic flow sensor has been developed to measure liquid or gas flows at ambient temperatures up to 300 ºC
and pressures up to 100 bar. While such environmental conditions are typical in pressurized steam systems in the oil and
gas industry (downhole and surface), wider applications are envisaged. The flow sensor uses a specially-designed bluff
body to generate vortex-induced pressure fluctuations as a function of flow. The pressure fluctuations result in
mechanical strain fluctuations in the sensor plate which is attached to the bluff-body. This is detected by means of a
Fibre Bragg Grating (FBG). The frequency of the pressure fluctuations is proportional to the flow velocity and is
measured by analyzing the spectrum of the FBG sensor signal. Flow velocity measurements ranging from ~1 m/s to ~25
m/s have been demonstrated. Special mechanical design, gluing and packaging processes have been developed to enable
applications at high temperatures and high pressures (HPHT). Although the working principle is the same as for
conventional vortex flow meters, this flow sensor does not require electronics, which is a great advantage at high
temperatures.
Biomedical Applications
3D visualization of tissue microstructures using optical coherence tomography needle probes
Rodney W. Kirk,
Robert A. McLaughlin,
Bryden C. Quirk,
et al.
Show abstract
Optical coherence tomography (OCT) needle probes use miniaturized focusing optics encased in a hypodermic needle.
Needle probes can scan areas of the body that are too deep to be imaged by other OCT systems. This paper presents an
OCT needle probe-based system that is capable of acquiring three-dimensional scans of tissue structures. The needle can
be guided to a target area and scans acquired by rotating and pulling-back the probe. The system is demonstrated using
ex vivo human lymph node and sheep lung samples. Multiplanar reconstructions are shown of both samples, as well as
the first published 3D volume rendering of lung tissue acquired with an OCT needle probe.
Fiber-based broadband ultrasound detector for photoacoustic imaging
Show abstract
Photoacoustic Imaging is an emerging imaging technology mainly for biology and medicine which combines
the advantages of diffuse optical imaging (high contrast) and ultrasonic imaging (high spatial resolution). A
short laser pulse excites the sample. The absorbed energy causes thermoelastic expansion and thereby launches
broadband ultrasonic waves. For collecting these waves we introduced integrating line detectors which integrate
the pressure along one direction. A fiber-based approach was realized using an interferometer integrated either
in glass fibers or polymer fibers. In this work we present the proof of principle of this approach.
A novel optical-fiber based surface plasmon resonance sensing architecture and its application to gastric cancer diagnostics
Show abstract
The management of threats such as pandemics and explosives, and of health and the environment requires the rapid
deployment of highly sensitive detection tools. Sensors based on Surface Plasmon Resonance (SPR) allow rapid, labelfree,
highly sensitive detection, and indeed this phenomenon underpins the only label-free optical biosensing technology
that is available commercially. In these sensors, the existence of surface plasmons is inferred indirectly from absorption
features that correspond to the coupling of light to the surface plasmon. Although SPR is not intrinsically a radiative
process, under certain conditions the surface plasmon can itself couple to the local photon states, and emit light. Here we
show for the first time that by collecting and characterising this re-emitted light, it is possible to realise new SPR sensing
architectures that are more compact, versatile and robust than existing approaches. It is applicable to a range of SPR
geometries, including optical fibres. As an example, this approach has been used to demonstrate the detection of a
protein identified as a being a biomarker for cancer.
Miniature temperature insensitive fiber optic sensors for minimally invasive surgical devices
Show abstract
This paper presents the concept of implementing miniature temperature insensitive optical fiber sensors into minimally
invasive surgical devices such as graspers, staplers and scissors. The lack of temperature insensitive and accurate force
feedback end effectors make the current minimally invasive surgeries (MIS) less effective especially in the area of
electrosurgery. The failure to provide accurate force feedback information reduces the user's sense of immersion in the
operating procedure. In this paper we present fiber sensors based on photonic crystal fibers (PCF) for force feedback
from the end effectors. Two types of miniature temperature insensitive PCF sensors can be implemented for MIS
applications; a Fabry-Perot interferometric sensor based on hollow core PCF and a tapered modal interferometric sensor
based on a solid core PCF. A concept for interrogating these sensors effectively at minimal cost is also presented. The
integration of sensors onto the end effectors is also important as one has to find an optimum position for maximum
strain/force transfer to the fiber sensor without interfering with the operation of the surgical tool. We have also presented
the methodology for incorporating the sensors into surgical end-effectors in this paper.
High sensitivity interferometric polymer optical fiber ultrasound sensors for optoacoustic imaging and biomedical application
Show abstract
The use of ultra wide-band ultrasonic fiber optic sensors in biomedical ultrasonic and optoacoustic applications is an
open alternative to conventional piezoelectric transducers. As they are non-metallic and non-electric sensors, they can be
combined with MRI in a multimodal imaging technique and can be made from biocompatible materials opening the
possibility for the fabrication of an optoacoustic endoscope. The acoustic sensitivity of the intrinsic fiber optic
interferometric sensors depends strongly of the material which is composed of. In this work we characterize and compare
experimentally the intrinsic ultrasonic sensitivities of three optical fibers: a single-mode silica optical fiber, a singlemode
polymer optical fiber and a multimode graded-index perfluorinated polymer optical fiber. All these optical fibers
can be used to construct an intrinsic interferometric optical fiber sensor for ultrasonic and optoacoustic applications with
frequencies in the range from 100kHz to 10MHz.
Dynamic analysis for mental sweating of a group of eccrin sweat glands on a human fingertip by optical coherence tomography
Show abstract
OCT is highly potential for in vivo observation of human sweating dynamics which affects activity of the
sympathetic nerve. In this paper, we demonstrate dynamic OCT analysis of mental sweating of a group of
eccrin sweat glands. The sweating dynamics is tracked simultaneously for nineteen sweat glands by
time-sequential piled-up en-face OCT images with the frame spacing of 3.3 sec. Strong non-uniformity is
observed in mental sweating where the amount of excess sweat is different for each sweat gland although the
sweat glands are adjacent to each other. The non-uniformity should be necessary to adjust as precisely the
total amount of excess sweat as possible through the sympathetic nerve in response to strength of the stress.
Poster Session: Bragg Gratings, Long Period Gratings, Specialized Gratings
Fiber Bragg grating sensor system using single-mode wavelength swept light source
Show abstract
This paper reports a high-performance FBG sensor system using a novel single-mode wavelength swept light source that
can sweep wavelengths with a spectrum line width of 1 pm, a sweep range of 135 nm, and a sweep frequency of 160 Hz.
This system can measure an FBG spectrum with 1-pm resolution and an FBG wavelength with 0.2-pm repeatability with
a measurement frequency of 160 Hz.
Fiber Bragg grating transverse load sensors using suspended core fibers for directional dependent strain measurement
Show abstract
This paper presents simulation and experimental results of orientation-dependent transverse load fiber sensors using fiber
Bragg gratings written in four-hole suspended core fibers. Resonant peak shifts and splitting of fiber Bragg gratings were
studied as functions of the applied transverse load and its orientation. Both simulation and experimental results revealed
that response of fiber Bragg grating in suspended core fibers are sensitive to both orientation and magnitude of transverse
strains.
Fibre Bragg gratings subject to high strain at high frequencies
Show abstract
A simple optical interrogation scheme based on an erbium doped fibre super-fluorescent source and a high Finesse Fabry
Perot driven at effective frequencies of 20 kHz over ~ 60nm range is used to recover the output signals from Fibre Bragg
Gratings (FBG) that can be deployed in a serial array. The FBG were modulated at frequencies up to 10 kHz and strains
up to ~4000μstrain. These signals were recovered in the time domain with a very high bandwidth digital scope using a
two dimensional waterfall display consisting of a number of segments where the time between segments is equal to the
inverse of the system scanning frequency; essentially the sequential 'x' axis tick markers in a conventional x-y graph
format. The amplitude induced changes in the wavelength of the FBG are converted to different times and observed as
sequential horizontal scans along the time axis of the waterfall, correspond to the variations in the wavelength of the
FBG (y axis). Signals from serial FBG arrays appear at different time slices on the time axis enabling near simultaneous
determination of the induced strain of each grating.
Displacement monitoring of switch track and its slab on a bridge of high speed railway by FBG
Show abstract
In a 350km/h high speed railway line, there is a seamless switch with ballastless slabs built on a bridge. 54 Fiber Bragg
Grating detecting cells are employed to monitor the displacement of track and slab. The cell is of extending function of
measurement range, up to 50mm displacement, and is of good linearity. Protecting methods for cells and fiber are
adopted to keep them surviving from the harsh conditions. The results show that in 75 days, the displacement of the track
and sleeper slab was 8-9mm, and the displacement is of high correlation with daily environmental temperature change.
Single coherence peak extraction among synthesized periodical peaks by different beat frequencies for elongation of measurement range in multiplexed long-length distributed FBG sensors
Show abstract
A scheme to extract only one coherence peak among multiple peaks synthesized in synthesis of optical coherence
function (SOCF) technique is proposed, and elongation of measurement range of multiplexed distributed long-length
FBG sensors is demonstrated. In the SOCF systems, distributed measurement is carried out by sweeping the position of a
coherence peak synthesized with optical frequency modulation of a laser source. Since, only one coherence peak is
allowed to exist in the measurement range for the distributed measurement, the measurement range was limited within
the interval of the peaks. In the proposed scheme, only one peak can be extracted among the multiple coherence peaks by
using different heterodyne beat frequency caused in each peak when the laser center frequency is swept in high speed for
shaping the FBG reflection spectrum. Extracted single peak is successfully swept over the conventional measurement
range in our multiplexed distributed long-length FBG sensor system.
Fiber Bragg grating interrogator for demonstration of spaceborne applications
Show abstract
Today's spacecraft employ hundreds of sensors. With spacecraft becoming increasingly complex, there is the need
for spaceborne measurement systems that are of low mass and volume, yet of high reliability and lifetime in the
harsh space environment. Targeted towards future applications in telecommunication satellites, the presented
FOSAT project aimes at a corresponding fiber-optic measurement system demonstrator. This goal particularly
calls for a vast number of sensors being multiplexed, enabling systems with a minuscle per-sensor mass, volume
and power share. To achieve this, several multiplexing techniques are jointly applied in the presented project to
form hybrid multiplexing. Furthermore, an interrogation technique which allows a dynamically adaptable tradeoff
between the number of sampled sensors and the sampling rate is employed to increase operational flexibility.
The design and the implementation of this unit are presented and a test result is summarized.
Magnetic field sensor based on magnetic fluid with side-polished fiber Bragg grating
Show abstract
A novel optical fiber magnetic sensor based on magnetic fluid is proposed in this paper. Stable nano-particle CoFe2O4magnetic fluid was synthesized firstly; the CoFe2O4 magnetic fluid was injected in capillaries containing side-polished
fiber Bragg grating (SPFBG) as sensing element. The reflected Bragg wavelength was changed by varying the magnetic
field which is perpendicular to the axial of SPFBG. Magnetic field sensing experiment show that 35pm of wavelength
shift at a magnetic field intensity of 16mT.
Static and dynamic strain fiber Bragg grating sensor interrogation using a monolithically integrated echelle diffractive grating
Show abstract
We report a miniaturized wavelength interrogator for the static and dynamic strain fiber Bragg grating sensors. The
developed interrogator is based on a monolithically integrated echelle diffractive grating and works in two independent
modes, one for the static strain measurement and the other for dynamic strain measurement. The proposed interrogator is
evaluated by measureing a static strain of 400 με and a dynamic strain of 200 Hz with a peak-to-peak amplitude of 200
με. Initial results are excellent and show that these two interrogation modes can be potentially performed
simultaneously.
Temperature-independent strain sensor based on four-wave mixing using Raman FBG laser sensor with cooperative Rayleigh scattering
Show abstract
A Temperature-independent strain sensor based on Four-Wave Mixing (FWM) using Raman fiber Bragg
grating (FBG) laser sensor with cooperative Rayleigh scattering is proposed. Two FBG were used to form
two linear cavities laser sensors based on Raman amplification combined with cooperative Rayleigh
scattering. Due to the low dispersion coefficient of the fiber, it is possible to obtain the FWM using the
two Raman FBG laser sensors. This configuration allows the operation as a temperature-independent
strain sensor where both sensors are sensitive to temperature but only one of the FBG is sensitive to
strain. The FWM efficiency is thus dependent on the applied strain but independent to the temperature.
Remotely tuneable optical filter based on polymer fibre Bragg grating
Show abstract
We propose a remotely tuneable optical Bragg grating filter written in polymer optical fibre (POF). Fibre optical
pumping in the fibre's absorption bands increases the fibre temperature, which causes a negative wavelength change of
the POF Bragg grating. By choosing a proper pumping wavelength remote tuning of the optical filter can be readily
realized without changing the gain of the optical signal.
Free water in fuel sensor using fiber long period grating
Show abstract
A fiber optic free water in fuel (WIF) sensor is proposed by utilizing a long period fiber grating (LPFG). The existence
of free water in fuel is indicated by the appearance of a characteristic loss band. The free water level in fuel can be
determined by measuring the transmissions of two characteristic loss bands.
Hydrogen detection in high pressure gas mixtures using a twin hole fibre Bragg grating
Show abstract
A sensor for detecting high-pressure hydrogen gas is presented that is based on Bragg gratings inscribed in a
microstructured twin hole optical fibre with femtosecond pulse duration 800 nm radiation and a phase mask. Utilising
the well-known variation of refractive index of silica upon exposure to hydrogen gas, the presence of hydrogen results in
a shift of the Bragg resonance. The use of a microstructured fibre design allows for more rapid diffusion of H2 into and
out of the fibre core resulting in faster detection of hydrogen gas compared to standard optical fibre. Grating inscription
with the femtosecond laser technique allows for sensor operation at high temperatures.
Probing of sapphire fiber Bragg gratings using intrinsic black-body radiation
Show abstract
Thermal radiation that is present when sapphire fiber Bragg grating sensors are operated at high temperatures (> 1000
°C) is used to obtain a spectral response of the grating without the use of an external optical source to probe the sensor.
Depending on the localization of the heat source, transmission or reflection type grating spectra can be obtained.
Benchmark for standard and computationally intelligent peak detection algorithms for fiber Bragg grating sensors
Show abstract
Implementation and comparison of peak detection algorithms for fiber Bragg gratings spectra have been implemented
and made publicly available. Benchmark experiments were performed by measuring accuracy, precision
and efficiency of currently used algorithms, namely the centroid, least squares gaussian and polynomial fitting,
and computational intelligence techniques using particle swarm optimization and perceptron neural network.
Considering noisy apodized and uniform FBG spectra in the detection, it is shown that there is no general
optimal algorithm for fast peak determination with high accuracy and precision, but it would be easier to choose
quasi-optimal algorithms with the more general guidelines presented.
Optimal design and implementation of a temperature and strain optical transducer using FBGs and fiber taper hybrid structure
Show abstract
A temperature and strain optical fiber transducer and its optimal design are presented. The hybrid structure is composed
of two Fiber Bragg Gratings (FBG) in a fused taper. Using the same phase mask one of the FBG is written outside of the
taper, and the other one in the middle of the taper, in the area with constant diameter. The taper diameter and the
structure length play a key role on the transducer behaviour. Useful results to optimize the transducer structure design,
from a theoretical and experimental investigation, are reported in this paper.
Application of simultaneous strain and temperature measurement technique using polarization maintaining fiber Bragg grating for distributed sensing based on OFDR
Show abstract
We have developed fiber-optic distributed sensors based on optical frequency domain reflectometry (OFDR). This
sensing system utilizes long-length fiber Bragg gratings (FBGs) and is able to measure strain or temperature distributions
with the high spatial resolution along FBGs. In this paper we inscribe a long-length FBG into Polarization-maintaining
AND Absorption-reducing fiber (PANDA-FBG) for simultaneous strain and temperature measurements. Applying
PANDA-FBG to OFDR system, we perform both simultaneous measurements and distributed sensing with a single
PANDA-FBG. In experiments we bonded the PANDA-FBG on a stainless beam and applied several steps of temperature
changes and four-point bending loads. We performed simultaneous measurements over the local area of the beam. Based
on the results, we compensated the temperature changes and calculated the strain distribution along the whole part of the
beam. The experimental results showed the applicability of this method.
Fiber Bragg grating interrogation technique for remote sensing (100km) using a hybrid Brillouin-Raman fiber laser
Show abstract
We propose and demonstrate the feasibility of a novel Fiber Bragg Grating interrogation technique for remote sensing
based on the use of a hybrid Raman-Brillouin fiber laser configuration. The laser comprises 100 km of standard singlemode
fiber (SMF) in a linear cavity configuration with four Fiber Bragg Gratings (FBGs) arranged in series. The FBGs
are used both for the sensing function and for the selection of the lasing wavelengths. A wavelength-swept laser pumps
Brillouin gain in the fiber cavity, which is previously set just under lasing threshold by the Raman gain. Furthermore, the
sensor signal is detected in the radio frequency domain instead of the optical domain so as to avoid signal to noise ratio
limitations produced by Rayleigh scattering. Experimental results demonstrate that the shift of the Bragg wavelength of
the FBG sensors can be precisely measured with good signal to noise ration when the FBG are used for temperature
sensing.
Polarization-switching FBG interrogator for wavelength-encoded polarization-sensitive measurements
Show abstract
We present an FBG interrogation system incorporating a fast polarization selection mechanism that enables the
independent detection of sensor responses to orthogonal polarizations. By configuring the polarization-switching
subsystem in two example schemes - switching between either orthogonal linearly or circularly polarized FBG
reflections - we demonstrate the system's capability to interrogate single transducers for both fiber bend and longitudinal
strain, or for both magnetic field strength and temperature. With each embodiment the capability for serial multiplexing
of sensors is retained. The technique allows magnetic field or bend to be measured using intrinsic multiplexable
wavelength-encoded sensors, and will be applicable to a number of other polarization-dependent measurements such as
electric field or transverse strain.
Microfiber Bragg grating for liquid-level variation sensing
Show abstract
We report a liquid-level variation sensor based on a fiber Bragg grating (FBG) inscribed in a 6.5-μmdiameter
microfiber. The proposed microfiber Bragg grating (MFBG) in air has two separated reflection
peaks, which are caused by the fundamental mode reflection and the higher-order mode reflection. Each of
the two peaks will split into another two adjacent peaks when a fraction of the MFBG sensor immerses into
liquid. By measuring the reflectivity difference between the two original peaks and their respective adjacent
liquid-induced peaks, the liquid-level variation can be determined.
Highly birefringent photonic bandgap Bragg fiber loop mirror for sensing applications
Show abstract
A highly-birefringent photonic bandgap Bragg fiber loop mirror sensor is proposed. Thanks to the Bragg
fiber geometry, one can observe the group birefringence and the bandgap fiber in the transfer function.
The sensing head presented different sensitivities for strain and temperature measurements. Using the
matrix method, both the physical parameters can be discriminated. It is important to highlight that this
Bragg fiber presents sensitivity to temperature of ~5.75 nm/ºC, for the group birefringence measurand.
Fibre Bragg grating vibration transducer based on novel mechanical sensing element for monitoring applications
Show abstract
We present a fibre optical accelerometer based on a balanced double cantilever design that offers improved performance
in terms of sensitivity, frequency range and reliability in general. Within a three year project funded by the Danish
National Advanced Technology Foundation, we have developed a rugged prototype with a wavelength sensitivity of
20 pm/g within ±1dB over a frequency range from DC to 1 kHz. These units are currently undergoing field tests in
monitoring applications, e.g. for wind turbines, energy services, aerospace etc. In particular, we consider sensitive and
reliable accelerometers essential for future condition monitoring and structural health monitoring applications.
Dual-polarization distributed Bragg reflector fiber lasers for hydrostatic pressure measurement
Show abstract
In this paper we report on polarimetric distributed Bragg reflector fiber laser sensor for hydrostatic pressure. Three
different types of active fibers were used to fabricate dual-polarization distributed-Bragg-reflector fiber lasers and their
responses to hydrostatic pressure were characterized. Three fibers shown different beat frequency response to hydrostatic
pressure and a maximum pressure sensitivity of 2.28 MHz/Mpa was obtained. By detecting the double frequency signal,
the sensitivity can be further increased to 4.56 MHz/MPa. We also tested the long term stability of the sensor at 300oC.
RF-frequency-division multiplexing of polarimetric fiber grating laser sensors
Show abstract
We demonstrated a method to trim the beat frequency of dual-polarization fiber grating lasers by exposing the laser
cavity to uniform UV beam. The UV-side-illumination induces an additional birefringence of the cavity fiber and
therefore permanently changes the beat frequency of the laser. The beat frequency can be trimmed to longer or shorter
frequency range in a large frequency range. A 6-channel RF-frequency division multiplexed polarimetric fiber grating
laser sensor array was demonstrated.
Realization of nano-order static strain resolution in FBG sensors using narrow linewidth tunable laser sources: theoretical analysis
Show abstract
The resolution of FBG static strain sensor interrogated with a narrow linewidth tunable laser is theoretically
analyzed. The main noise sources of the sensor are analyzed. The expression of the resolution is deduced with crosscorrelation
algorithm. The calculated resolution agrees well with previous experimental result, and the analysis is further
validated by numerical simulation. Based on the deduced expression of resolution, the guidelines to optimize the sensor
for realization of high resolution are given in detail. It is shown that with properly designed FBG and interrogation
system, nano-order static strain resolution can be realized as we demonstrated in experiment recently.
High-speed full-spectrum fiber Bragg gratings interrogator system and testing
Show abstract
This paper presents a high repetition rate fiber Bragg grating (FBG) interrogation system that is able to capture the entire
reflection spectrum at a rate of up to 300 kHz. The system uses a high speed MEMS based tunable optical filter that is
driven with a sinusoidal voltage. The time varying FBG reflection spectrum in transmitted through the tunable filter.
The time varying signal is then mapped into time varying reflection spectra. This interrogation system is used during
two dynamic strain tests, in which the reflection spectra are measured at a repetition rate of 100 kHz. The first test is the
impact of a woven carbon composite and the second test is on an electromagnetic railgun.
A novel FBG-based fence with high sensitivity and low nuisance alarm rate
Show abstract
A quasi-distributed FBG-based fiber-optic fence is investigated in this paper. A novel intrusion detection method is
proposed based on the autocorrelation characteristics of the signal with and without disturbances, which is very effective
to detect extremely weak signals even from nonequivalent sensor nodes in a large sensor network. When analyzing the
intrusion signal's characteristics and excluding the false alarm sources, such as environmental interferences and others,
Nuisance Alarm Rate (NAR) is well controlled while extremely high Probability of Detection (PD) is assured. The
experimental results show that the PD of the fiber fence using these methods for detecting the single and multiple events
can be both higher than 99.5%, while the NAR can be controlled well below 0.5%.
A fast response tilted fiber Bragg grating fluid refractometer using an exposed-hole microstructured optical fiber
Show abstract
A fast response tilted fiber Bragg grating fluid refractometer using an exposed-hole microstructured optical fiber is
proposed and analyzed. The theoretical and simulation results show that a sensitivity of 5.40×10-5 r.i.u within a diffusion
limited response time of 6 s could be achieved. This exposed-hole configuration can be used to construct a fluid
refractometer for achieving a fast response, high sensitive distributed detection.
A fast response suspended core fiber optical gas sensor with side-opening and micro-holes configurations
Show abstract
A fast response suspended core fiber optical gas sensor configuration using side-opening hole and micro-holes array
structure on the thin layers is proposed. The side-opening-hole structure enables a fast filling speed of gases into the
opening-up-hole region, while the micro-holes array on the thin layers ensures that gases could further diffuse into
the other holes columns quickly. Meanwhile, its sensitivity could be tripled in contrast to the previous structures.
Simulation results show that a diffusion limited response time of 12 s could be realized and thus move a step further
toward real-time sensing applications.
FBG-based vibration measurement of rotating structure using optical fiber rotary joint
Show abstract
We construct an intensity-based FBG sensor for a vibration measurement of a rotating structure by using an optical
fiber rotary joint (OFRJ) which enables free rotation of fiber while maintaining low-loss coupling efficiency. Although
a number of FBG sensors have been proposed for use in various applications, they have not yet been applied to a
rotating structure especially for dynamical measurement. In the proposed sensor system, an SOA-based dualwavelength
fiber laser is employed as an optical source and an additional reference FBG sensor is multiplexed with the
intensity-based FBG sensor by use of a wavelength division multiplexing (WDM) technique. The reference sensor
enables to compensate the insertion-loss variation due to the rotating OFRJ so that a real-time vibration measurement of
a rotating structure is achieved in the intensity-modulation scheme. In the experiment, the operation principle is
successfully confirmed, and the vibration measurements of a rotating cantilever beam and a propeller-like plastic blade
are demonstrated.
Linearly chirped and weakly tilted fiber Bragg grating edge filters for in-fiber sensor interrogation
Show abstract
Power-referenced in-fiber edge filters based on a linearly chirped and weakly tilted fiber Bragg gratings (TFBG) are
proposed and experimentally demonstrated. A strongly chirped TFBG with a polymer coating provides a smooth transfer
function with up to 0.7 dB/nm of discrimination over the C-band. The slope profile of UV-induced chirped TFBG can be
easily tailored by adjusting the tilt angle using only one chirped phase mask. Interrogators based on chirped TFBG can
provide temperature-self-compensated, broadband, robust and cost-effective in-fiber demodulation for FBG sensing
applications.
Fast wavelength-swept dispersion-tuned fiber laser over 500kHz using a wideband chirped fiber Bragg grating
Show abstract
We proposed a wide and fast wavelength-swept fiber lasers based on the dispersion tuning for the optical coherence
tomography (OCT) applications. So far, we have achieved the sweep rate of ~200kHz at the sweep bandwidth of
~180nm. The sweep rate is only limited by the photon lifetime, which is proportional to the cavity length. Since we used
a dispersion compensating fiber (DCF) as the dispersive medium, the long cavity length (~100m) was the limit of the
sweep rate. In this paper, we demonstrate faster sweep rate up to ~500kHz by using a wideband chirped fiber Bragg
grating (CFBG).
Etched fiber Bragg grating sensing system thermically assisted for analysis of water- ethanol mixtures
Show abstract
This work presents a sensing system based on an etched fiber Bragg grating, applied to the refractometric analysis of
water-ethanol mixtures. The system configuration employs one etched-FBG operating at two temperatures, (20.0 ± 0.5)
°C and (3.0 ± 0.5) °C. The sensing system performance in measuring the ethanol-water proportions is evaluated in the
concentration range between 0.0 and 100.0 % v/v of water in ethanol, resulting in uncertainties less than 3.9 % v/v. The
sensor capability to determine the ethanol concentration is shown, even for the range of concentrations where the
correlation between refractive index and ethanol proportion in the sample presents an ambiguous behavior.
Linear FBG interrogation with a wavelength-swept fiber laser and a volume phase grating spectrometer
Show abstract
We propose a novel FBG (fiber Bragg grating) sensor system that uses a tunable wavelength laser and a
volume phase grating spectrometer. The effect of nonlinear wavelength scanning and uneven power profile
of the fiber laser, which substantially degrades the measurement accuracy, is minimized by using a
spectrometer demodulation. The constructed sensor system showed linear output according to the Bragg
wavelength variation, and showed much higher signal-to-noise ratio compared to the conventional
spectrometer demodulation which used much dimmer broadband light sources.
Three parameters simultaneous measurement with a single TFBG
Show abstract
A sensor for simultaneous measurements of strain, temperature and refractive index (RI) is proposed. The device is based
on a single 8º tilted fiber Bragg grating (TFBG). Monitoring the core mode and ghost mode wavelength, it is possible to
discriminate strain and temperature. The RI measurement is obtained through computation of the transmission spectrum
area. Resolutions up to 4 με, 3.1 ºC and 5.7 x10-4 were achieved. The present sensor can be an important tool in the
sensing field.
Thermal characterization of FBG strain gauges for the monitoring of the cupola of Duomo di Milano
Show abstract
The incoming restoration works of Duomo di Milano main spire requires a continuous structural health monitoring of the
cupola supporting it. For reasons mainly connected to the lightning hazard, fiber optic sensors have been selected, based
on FBG technology. Strain of the lower part of the vaulting-rigs inside the octagonal cupola is the measurement of
interest. Being the expected signals very small and the thermal disturbances very important, a thermal characterization of
two types of commercial strain gauges was carried out in laboratory with a thermal chamber and a block of the same
marble used for the Duomo construction. This allowed to find a relationship later used to compensate any thermal
effects, leading to the extraction of the mechanical load contribution only. An uncertainty analysis gave a result of 5 to
10 μm/m in the tested temperature range -5 °C to +40 °C. The future work will expand the monitoring system to more
measurement points and it is expected this can provide an important diagnostic tool during restoration operations.
Performance of a high-temperature sensor based on regenerated fiber Bragg gratings
Show abstract
In this paper we have studied the performance of a high-temperature packaged sensor based on Regenerated
Fiber Bragg Gratings (RFBGs). The packaging consists of a two-bore ceramic tube and a 1.5 mm-thick metal
casing. The optical response of packaged and unpackaged RFBG sensors for temperature measurements up to
1100°C have been evaluated and compared to each other. Especial attention has been placed on possible
residual hysteresis in the thermo-optical response after several temperature cycling tests. The response and
recovery times of the packaged sensor has been also measured. The former has been found to be comparable
to that of commercial thermometers based on conventional thermocouples.
Strain monitoring in power cables of offshore wind energy plants with femtosecond laser inscribed fibre Bragg gratings
Show abstract
A fibre Bragg grating sensor system used for monitoring of strain being effective on the power cable of an offshore wind
turbine is presented. The Bragg grating structure was inscribed in coated non-photosensitive standard telecommunication
fibres using an infrared femtosecond laser and the point-by-point writing technique. Due to the presence of the protective
coating of the fibre, the mechanical stability of the resultant sensor device is better than that of a sensor consisting of a
bare fibre. A system containing this sensing element was successfully installed and tested in an offshore wind turbine
prototype (REpower 6M) in February 2010, near Ellhöft (Germany). The fabrication process of the fibre Bragg gratings,
a comparison between the sensor signal and a commonly used strain gauge and measurement results of the online
monitoring are presented.
Resonant hydrophones based on coated fiber Bragg gratings. Part II: experimental analysis
Show abstract
Here, we report on recent experimental results obtained with Fiber Bragg Grating (FBG) hydrophones for underwater
sound pressure detection. Investigated optical hydrophones consist of FBGs coated with ring shaped polymers of
different size. Coating material has been selected to provide mechanical amplification through a low elastic modulus
combined with acoustic impedance matching. Underwater acoustic measurements carried out in the range 4-35KHz
reveal a resonant behaviour depending on the coating size. This behaviour is consistent with numerical analysis
performed using finite element method and presented in part I. In addition, good linearity was observed versus local
sound pressure demonstrating a minimum detectable sound pressure of few Pascal.
Resonant hydrophones based on coated fiber Bragg gratings. Part I: numerical analysis
Show abstract
In this work, we report the first evidence of the resonant behavior of underwater acoustic sensors constituted by a Fiber
Bragg Grating (FBG) coated by a ring shaped overlay. The complex opto-acousto-mechanical interaction among an
incident acoustic wave travelling in water, the optical fiber surrounded by the ring shaped coating and the FBG inscribed
in an optical fiber is numerically analyzed by means of a commercial multiphysics software (COMSOLtm) implementing
the finite element method. The numerical analysis has been performed in the frequency range 0.5-30 kHz, typically used
in sonar applications. The retrieved numerical results, describing the opto-acoustic response of the optical hydrophone,
highlighted that the coating is able to notably improve the sensitivity of the hydrophone, in the whole investigated
frequency range, when compared to a FBG without coating. Furthermore, the hydrophone sensitivity versus the
frequency presents characteristic resonances, which strongly improve the hydrophone opto-acoustic sensitivity with
respect to the sensitivity background far from the resonances. As ascertained by means of a three-dimensional modal
analysis of the hydrophone, the composite cylindrical structure of the sensor acts as an acoustic resonator accorded to the
frequencies of the longitudinal vibration modes of the composite structure. In order to provide a full description of the
sensor performances, we carried out also a parametric analysis by varying the geometrical and mechanical properties of
the coating. The numerical results, besides outlining the resonant behavior of the coated FBG, also provided a tool for
the design and optimization of the sensor performances which in turn can be tailored for specific Sonar applications.
Impact of hydrogen-induced effects on optical fiber Bragg gratings
Show abstract
The effects induced by low and high pressure ingression of hydrogen on UV-written germanium doped silica optical
fiber Bragg gratings-at room and high temperature-are studied and discussed. Results show that at elevated
temperatures (>150 °C), an immediate and permanent shift of the peak grating reflectivity is induced and proportional to
the hydrogen concentration (10 pm/AtmH2), whilst at room temperature most of the grating spectrum changes are
transient and mostly reversible.
Miniature fiber Bragg grating strain rosette based on lossless tapers
Show abstract
A miniature fiber Bragg grating strain rosette is presented. The proposed design is made possible through
the development of low curvature radius lossless tapers, thus offering advantages in miniaturization of the
rosette configuration. We report on the experimental validation of the miniature rosette design,
demonstrating its effective operation.
Monitoring the hysteresis effects in the strain-stress curve of carbon fiber reinforced laminates by FBG technology
Show abstract
In this paper, we present a study of detecting the hysteresis effect in strain-stress curve of carbon fiber reinforced
materials by Fiber Bragg Grating technology. By calculating the dissipative energy density contoured by hysteresis
loops, this method can be further applied in detecting the cracks and fatigue of carbon fiber reinforced laminates. In
contrast to the traditional sensors, such FBG sensors have numerous merits, such as small size, immunity to
Electromagnetic Interference and easy installation into the carbon fiber reinforced laminates. This method can also be
extended into monitoring other materials which also exhibit hysteresis effects in their strain-stress curves.
Cognitive fiber Bragg grating sensors system based on fiber Fabry-Perot tunable filter technology
Show abstract
The wavelength demodulation based on a Fiber Fabry-Pérot Tunable Filter (FFP-TF) is a common method for
multiplexing Fiber Bragg Grating (FBG) sensors. But this method cannot be used to detect high frequency signals due to
the limitation by the highest scanning rate that the FFP-TF can achieve. To overcome this disadvantage, in this paper we
present a scheme of cognitive sensors network based on FFP-TF technology. By perceiving the sensing environment,
system can automatically switch into monitoring signals in two modes to obtain better measurement results: multi
measurement points, low frequency (<1 KHz) signal, and few measurement points but high frequency (~50 KHz) signals.
This cognitive sensors network can be realized in current technology and satisfy current most industrial requirements.
Response of some pi-phase-shifted Bragg gratings to elevated pressure
Show abstract
The effect of pressures up to 200 kPa on pi-phase-shifted Bragg gratings was investigated in several types of
fibers placed in a pressure chamber. Standard and alternative types of pi-phase shifted gratings were studied,
and changes in reflection spectra caused by pressure changes were monitored. The alternative pi-phase shifted
grating was fabricated using a phase mask with 536-nm pitch exhibiting features at twice the Bragg
wavelength near 1552 nm due to the interleaved refractive index modulations along the fiber core with the
periodicity of the phase mask. The three gratings studied exhibited quite different variation in Bragg
wavelength with increased pressure for the different fiber types, and the alternative pi-phase-shifted grating in
Corning HI 1060 FLEX fiber also suffered a significant change in the shape of the peaks.
Fiber Bragg grating microphone system for condition-based maintenance of industrial facilities
Show abstract
This paper presents a multipoint fiber Bragg grating (FBG) sensing system operating as a precision microphone. This
instrument aims to become the best performing technology for condition-based maintenance (CBM) of critical elements,
like ball bearings and cogwheels, embedded in industrial manufacturing machineries. The system architecture is based
on the simple matched-laser principle, leading to a low-cost and high-sensitivity system, operating in time and
wavelength multiplexing mode. Then, heavy signal processing is applied, providing an outstanding performance
improvement of 59 dB in terms of signal-to-noise ratio. A demonstration of condition-based maintenance operation has
been performed using standard models of ball bearing sound spectra. Compared to traditional microphones applied to
CBM, the signal processing-powered FBG system provides remarkable advantages in terms of sensitivity and rejection
of environment noise, providing an improvement of cost-effectiveness of CBM.
High speed, high-resolution fiber Bragg grating sensing system for monitoring of weigh-in-motion devices
Show abstract
We present a fast high-resolution fiber Bragg grating sensing system for weigh-in-motion (WIM) application. The
proposed system makes use of standard telecom photonics components operating at high speed and with insufficient
resolution; then, using signal processing we artificially improve the accuracy of the system down to 1 με. This way, the
proposed architecture overcomes the state of the art of optical systems for WIM, which cannot cope with both high
resolution and high frequency requirements. The developed system has been applied to a prototype weigh-in-motion
device, which consists of a road speed bump. Structural deformations of the bump when perturbed by a thin-footmark
load are well reproduced. Using multiple Bragg grating sensors, it is possible to unambiguously determine position and
weight of a moving load on the bump with accuracy of 0.2 - 1.2 kg.
Wheel flat detection in high-speed railway systems using fiber Bragg gratings
M. L. Filograno,
P. Corredera,
M. Gonzalez-Herraez,
et al.
Show abstract
Wheel "flats" are a major source of problems in railway systems since they cause strong wear both in the infrastructure
and in the train vehicles. In this work we present field tests concerning the application of Fiber Bragg Grating (FBG)
sensors for the detection of out-of-roundness in high-speed train wheels. Wheel flats are shown to cause high-energy
impacts on the rails which can be monitored using FBGs located in the rails. The results point out a great potential of this
technology for the development of wheel flat detection systems.
All-fibre twist sensor system based on 45° and 81° tilted fibre gratings
Show abstract
We experimentally demonstrated a highly sensitive twist sensor system based on a 45° and an 81° tilted fibre grating
(TFG). The 81°-TFG has a set of dual-peaks that are due to the birefringence induced by its extremely tilted structure.
When the 81°-TFG subjected to twist, the coupling to the two peaks would interchange from each other, providing a
mechanism to measure and monitor the twist. We have investigated the performance of the sensor system by three
interrogation methods (spectral, power-measurement and voltage-measurement). The experimental results clearly show
that the 81°-TFG and the 45°-TFG could be combined forming a full fibre twist sensor system capable of not just
measuring the magnitude but also recognising the direction of the applied twist.
Numerical comparison of peak detection algorithms for the response of FBG in non-homogeneous strain fields
Show abstract
The increasing use of Fiber Bragg Grating (FBG) in many fields, such as smart structures and structural health
monitoring, requires a detailed analysis of the measured values from the optical interrogators. While the peak detection
of each FBG reflection spectra is relatively simple if the strain profile is constant all over the FBG sensor, special care
must be paid when the strain profile is unknown, or non-homogeneous for sure. The objective of this work is to develop
a numerical model able to simulate the whole measurement process, from the strain profile to the measured peak
wavelength. The numerical simulation include a T-matrix model and some of the most used peak detection algorithms.
The results obtained with some of the tested strain profiles show that the measured errors can be important.
Nickel plating of FBG strain sensors for nuclear applications
Marcus Perry,
Pawel Niewczas,
Michael Johnston,
et al.
Show abstract
We present a method for plating FBG strain sensors with a strongly-bonded, hermetic nickel layer, without exposure of
the fiber to corrosive environments. A 1μm thick, highly adhesive chrome layer is deposited onto bare fibers via
evaporation. Addition of an inert and electrically conductive gold layer then allows the fiber to be electroplated with a
50-100μm nickel layer. Finite element models have confirmed that nickel plated FBG sensors can be brazed into steel
structures and used to monitor local strain and temperature. Embedding gratings that are temperature and radiation
resistant will be particularly applicable to the structural health monitoring of steel prestressing tendons used in the
concrete containments of nuclear power plants and other safety-significant structures.
Nonlinear-programming optimized fiber Bragg grating based force-torque-sensor with six degrees of freedom
Show abstract
Force-torque sensors are key elements in modern force feedback and robotic control applications. For special applications
resistance against electromagnetic interference, high amount of load cycles or chemical resistance are important. For these
applications, fiber-Bragg-grating based force torque sensors have been seen as possible solutions. Yet the implementation
of a force-torque-sensor with six degrees of freedom and well conditioned sensitivities is still lacking demonstration. In
this work, we demonstrate the design of a miniaturized fiber-Bragg-grating based force-torque sensor with six degrees
of freedom using a numerical nonlinear programming technique. We implement the optimized structure and show its
feasibility and sensitivity.
Pressure sensor using carbon fiber laminate tube and fiber Bragg grating
Show abstract
In this paper, a novel pressure sensor based on carbon fiber laminate tube (CFLT) and fiber Bragg grating is proposed.
Theoretical analysis and investigation are conducted. Experiment results indicate that the pressure sensitivity is
138pm/MPa. Pressure sensitivity is improved due to the hollow tube structure compared with solid structure of pressure
sensor that we proposed before.
Bragg wavelength-insensitive fiber Bragg grating ultrasound detection system based on a fiber ring laser
Show abstract
A fiber Bragg grating (FBG) ultrasound detection system incorporating a fiber ring laser was developed. In the
system, an FBG was used not only as a sensor but also as the ring cavity mirror. The fiber ring laser emitted
lasing light at the Bragg wavelength of the FBG sensor and the intensity of the lasing light varied with
ultrasonic vibration applied to the FBG sensor. The system proved to detect ultrasonic response consistent with
the characteristics of the ultrasound impinging on the FBG and to have ultrasound sensitivity enough to detect
acoustic emission. This system is quite simple configuration and small in size. Moreover, this system can work
irrespective of the Bragg wavelength of the FBG sensor.
Side polished fiber Bragg grating sensor for simultaneous measurement of refractive index and temperature
Show abstract
A fiber sensor to achieve simultaneous measurement of refractive index and temperature is proposed by using a side
polished fiber Bragg grating. The reflective wavelength of side polished fiber Bragg grating shifts with the ambient
refractive index and local temperature. By overlaying half of the polished surface of fiber Bragg grating with liquid
material, simultaneous discrimination of liquid refractive index and local temperature with dual reflective Bragg
wavelengths is demonstrated. The refractive index sensitivity is from 4.99nm/riu to 252.78nm/riu when refractive index
changes from 1.4098 to 1.4479, and the temperature sensitivity is 0.012nm/°C.
Fiber Bragg grating cantilever sensor system for fluid flow monitoring with temperature compensation
Show abstract
A fiber-optic sensor system based on fiber Bragg gratings (FBGs) is proposed and demonstrated to realize water flow
measurement with temperature compensation capability. For the FBG cantilever sensor as the key component of the
sensor system, a change in the water flow rate gives rise to a monotonic shift in the Bragg wavelength of the grating
while the flow direction results in either a redshift or blueshift in the Bragg wavelength due to a stretched or shrunk state
of the grating. The resolutions of the sensor system for the forward and backward flow measurement are 58.1 and 166.7
cm3/s, respectively.
Temperature-insensitive 2D tilt sensor with two chirped fiber Bragg gratings
Show abstract
A novel temperature-insensitive tilt sensor is proposed by embedding two chirped fiber Bragg gratings (CFBGs) into a
cylindrical cantilever-based pendulum in two orthogonal planes. Due to the tilt-induced nonuniform strain field applied
along the length of the CFBGs, their bandwidths of reflection spectra vary with the applied tilt angle. By measuring the
reflected optical powers of the two CFBGs illuminated by a flattened broadband light source, temperature-insensitive
measurement of both inclination angle and direction in two dimensions can be realized. Theoretical calculations and
preliminary experimental results verified the feasibility of the proposed sensor design. The measurement is in real-time
manner and the sensor is cost-efficient because it is an intensity-modulated sensor.
100-km long distance FBG vibration sensor based on matching filter demodulation
Show abstract
A 100-km long distance fiber Bragg Grating (FBG) vibration sensor system is demonstrated by using a Raman pump
laser source at 1395 nm and two segments of erbium doped fiber (EDF). The reflected spectrum of FBG has 30dB signal
noise ratio. By using a wavelength matched FBG to achieve wavelength demodulation, vibration frequencies from 1Hz to
1000Hz has been effectively detected in this 100km long distance vibration sensor system.
Hydrogen sensor based on side-polished fiber Bragg gratings coated with thin palladium film
Show abstract
A hydrogen sensor based on side-polished fiber Bragg grating (FBG) coated with Pd thin film by magnetron sputtering is
proposed. Hydrogen concentration is correlated with the shift of FBG central wavelength, since refractive index change
in hydrogen sensitive Pd coating deposited on side-polished FBG affects the effective refractive index of FBG, and
therefore Bragg wavelength is shifted. Experimental results demonstrate that FBG wavelength shifts to lower wavelength
as the hydrogen concentration increases. The proposed optical fiber hydrogen sensor shows 15pm wavelength shift in
0.01% volume percentage of hydrogen concentration, and totally 246pm offset exists in pure hydrogen environment.
Liquid core fibre Bragg grating based refractive index sensor formed by femtosecond assisted chemical etching technique
Show abstract
We report the fabrication of a refractive index (RI) sensor based on a liquid core fibre Bragg grating (FBG). A micro-slot
FBG was created in standard telecom optical fibre employing the tightly focused femtosecond laser inscription aided
chemical etching. A micro-slot with dimensions of 5.74(h) × 125(w) × 1388.72(l) μm was engraved across the whole fibre
and along 1mm long FBG which gives advantage of a relatively robust liquid core waveguide. The device performed the
refractive index sensitivity up to about 742.72 nm/RIU.
Monitoring the junction temperature of an IGBT through direct measurement using a fiber Bragg grating
João Paulo Bazzo,
Tiago Lukasievicz,
Marcio Vogt,
et al.
Show abstract
This paper proposes a new technique to monitor the junction temperature of an insulated gate bipolar transistor (IGBT)
through direct measurement using an optical fiber sensor mounted on the chip structure. Some features of the sensor such
as electromagnetic immunity, small size and fast response time allow the identification of temperature changes generated
by the energy loss during device operation. In addition to the online monitoring of the junction temperature, results show
the thermal characteristics of the IGBT, which can be used to develop an accurate model to simulate the heat generated
during the device conduction and switching processes.
Fiber Bragg grating sensors embedded in concrete samples for a normalized fire test
Show abstract
Optical fiber sensors based on Fiber Bragg Gratings (FBG) have been embedded in concrete samples for temperature
measurement. Three different types of gratings have been used in this experiment: FBGs inscribed in photosensitive
germanium-boron codoped fiber and Regenerated Fiber Bragg Gratings (RFBG) inscribed in germanium doped and in
germanium-boron codoped fiber. The concrete samples were placed inside a fire chamber where the temperature was
increased above 1000ºC as described in the Spanish/European standard UNE-EN 1363-1 temperature profile for concrete
resistance to real fire. The temperature was monitored in real time. We have compared the performance of the optical
sensors and electrical thermocouples. The RFBGs have shown a very good performance while the FBGs are able to
monitor high-temperatures until their disappearance.
Simulation of FBG sensing networks using CDM + SDM
Show abstract
To increase the multiplying density of FBG sensors, a novel FBG sensing network using CDM + SDM by coding
measuring points directly is proposed, which increases the multiplying density greatly and is easy to implement in
engineering for its simple structure. Simulation of an example using (25,3,1)-OOC code indicates that although the
system's multiplying density increased greatly, its measuring precision decreased.
FBG sensor system based on wavelength-swept active mode-locking laser with RSOA gain medium
Show abstract
We performed an experiment of wavelength-swept laser based on active mode-locking on reflective
semiconductor optical amplifier (RSOA). Since this laser does not have a wavelength-selecting filter, it can
achieve a high sweeping speed and reduce the component cost and size. Compared to the conventional SOA
gain medium, RSOA shows a merit of higher efficiency of cross gain modulation due to the twice propagation
of active gain region. We applied this laser to Fiber Bragg grating (FBG) strain sensor system which can have
faster data acquisition speed than conventional wavelength-swept laser method. The linear response of FBG
peak for the applied strain is monitored using the proposed laser source.
Cladding modes FBG curvature sensor based on a core misaligned splice
Show abstract
A novel fiber optic curvature sensor based on a core-offset single-mode fiber (SMF) and on a fiber Bragg grating (FBG)
is presented. The FBG cladding modes are efficiently excited by the large core misalignment. The curvature of the beam
can be obtained by the reflected power of the core mode and the recoupled cladding mode.
Simple CW correlation OTDR for interrogation of multiplexed low-reflectivity FBG sensors
Show abstract
We propose a very simple technique for multiplexing and interrogation of Fiber Bragg Gratings using a DFB diode
laser operating in CW mode. The technique is based on correlation detection of probe signals reflected by the fiber
Bragg gratings. Phase noise of the DFB diode laser converted into intensity noise was used as a probe signal.
Demultiplexing was performed by calculating the correlation between the probe signal and the signal reflected by the
fiber. The correlation function provide the reflectivity at the probe wavelength and position of each fiber Bragg gating.
Reflection spectra of FBGs can be obtained by tuning the diode laser wavelength with temperature and calculating the
correlation function for each probe wavelength. Results of experimental verification of the technique are presented.
Monitoring of vacuum assisted resin transfer moulding (VARTM) process with superimposed Fiber-Bragg-gratings
Show abstract
We report the instrumentation of a manufacturing composite process using an optical fiber sensor based on Bragg
gratings. The sensor is made of superimposed Long Period (LPG) and short period (FBG) Bragg gratings written in the
same fiber section. The monitoring of the process needs simultaneous measurements of temperature and strain. It has
been shown that these two solicitations can be determined and discriminated with a superimposed FBG/LPG sensor [1].
In this paper we present the device based on the dual superimposed gratings. The sensor is embedded in a composite
specimen manufactured by Vacuum Assisted Resin Transfer Moulding (VARTM) process for monitoring purpose.
870nm Bragg grating in single mode TOPAS microstructured polymer optical fibre
Show abstract
We report the fabrication and characterization of a fiber Bragg grating (FBG) with 870 nm resonance wavelength in a
single-mode TOPAS microstructured polymer optical fiber (mPOF). The grating has been UV-written with the phasemask
technique using a 325 nm HeCd laser. The static tensile strain sensitivity has been measured as 0.64 pm/μstrain,
and the temperature sensitivity was -60 pm/°C. This is the first 870nm FBG and the first demonstration of a negative
temperature response for the TOPAS FBG, for which earlier results have indicated a positive temperature response. The
relatively low material loss of the fiber at this wavelength compared to that at longer wavelengths will considerably
enhance the potential utility of the TOPAS FBG.
Acousto-optic control of the LPG spectrum for sensing applications
Show abstract
Experimental and numerical demonstration of the acousto-optic effect applied in long period grating by means of
flexural waves is presented. The interaction between acoustic and optical waves is modeled with help of the method of
assumed modes, which delivers the strain field inside the grating and the transfer matrix method, which, given the strain
field as input, calculate the resultant grating spectrum. The experimental and theoretical results are found to be in good
agreement. The main effect of the bends in the grating is the break of degeneracy of the circular cladding modes, leading
the attenuation band to be changed. Among all the applications of this methodology, it is important to mention the
possibility of use as a tunable filter, laser cavity gain controller, switching device and transducer in sensing systems.
Tapered long-period fiber gratings working in inverted mode through all-fiber ring shaped illumination
Show abstract
In this work we present the possibility to obtain long-period fiber gratings (LPFGs) working in inverted mode through
simple and cost effective all-fiber ring shaped illumination. Permanently and locally bent single-mode optical fibers are
used to provide a ring shaped illumination with core mode depletion depending on the bend features. When this kind of
illumination interacts with a tapered LPFG, light power transfer from input cladding modes towards the core mode
occurs depending on the grating characteristics. The final result is a transmission spectrum with zero transmission in the
whole spectral range except for the optical wavelengths corresponding to mode coupling. Two important aspects of the
proposed structure can be envisaged. The first one relies on the possibility to additionally obtain mode coupling
involving asymmetric cladding modes by modifying the illumination symmetry acting on the bend shape. The second
one is the possibility to tune the visibility of the peaks corresponding to the coupled cladding modes by changing the
surrounding medium on the straight fiber located after the bent region without involving the LPFG section. Here, both
aspects have been experimentally demonstrated and their effectiveness proved in sensing applications involving
refractive index measurements. The proposed approach thus opens up new sensing architectures as well as new fluidic
filters for communication applications.
Response of hydrogel coated cascaded long period gratings to relative humidity
Show abstract
The response of transmission spectrum of cascaded long period gratings with hydrogel coating to relative humidity is
investigated experimentally. Two configurations in terms of coated/not coated areas of the cascaded LPGs are explored
to gain a significant enhancement of RH sensitivity. For humidity level greater than 50%RH, the visibility of the
interference fringes is highly sensitive to relative humidity, showing a good linearity. The sensitivities of the two
proposed hydrogel coated cascaded LPGs devices are 7.71 × 10-3/%RH and 7.08 × 10-3/%RH, respectively. RH
accuracies of ± 0.45% and ± 0.32% are achieved, respectively.
Photonic-crystal-fiber-based surface long-period fiber grating for simultaneous measurement of temperature and ambient index
Show abstract
A simple scheme for discrimination of temperature and ambient index based on a D-shaped photonic crystal fiber
with surface long-period fiber gratings depending on input polarization state are proposed and experimentally
investigated.
Flow cell with hybrid LPG and FBG optical fibre sensor for refractometric measurements
Show abstract
The combination of a long period grating and a fiber Bragg grating written on the same fiber is described as method to
reduce noticeably the interferences caused by strain and temperature in the measurement of refractive index. The hybrid
LPG and FBG optical fiber sensor is manufactured and located in a small volume flow cell. The whole system with its
flow cell and the gratings fabrication are extensively described as well as both the acquisition and data processing. The
maximum sensor sensitivity and resolution are about 3120 nm/RIU and 2 x 10-5 RIU, respectively.
Femtosecond laser inscribed superstructure fibre gratings
Show abstract
We demonstrate the development of femtosecond laser inscribed superstructure fiber gratings (fsSFG) in silica optical
fibre. We utilise a single step process, to inscribe low loss and polarisation independent, sampled gratings in optical
fibres using the point by point femtosecond laser inscription method. Our approach results in a controlled modulated
index change with complete suppression of any overlapping LPG structure leading to highly symmetric superstructure
spectra, with the grating reflection well within the Fourier design limit. We also solve Maxwell's equations and calculate
the back reflection spectrum using the bidirectional beam propagation method (BiBPM). Experimental results validate
our numerical analysis and the estimation of inscription parameters such as ac index modulation, wavelength and the
relative peak strength. We also explore how changes in the grating's period influence the reflection spectrum.
Mechanical stress sensors using micromachined grating fibers
Hironori Kumazaki,
Munehiro Hiramatsu,
Hisakazu Oguri,
et al.
Show abstract
We discuss mechanical stress sensors based on fiber Bragg gratings (FBGs) micromachined by anisotropic
reactive ion etching (RIE) using CF4 plasma. Locally thinned FBGs have the potential to be used as sensitive strain
sensors whose sensitivities increase with decreasing measurement range. The center reflection wavelength shift rate of an
etched and thinned grating (thinned grating length: 2.0 mm; thinned diameter: 15 μm; total grating length: 10.0 mm) was
approximately 15 times greater than that of a conventional unprocessed FBG. The difference in the center reflection
wavelengths of thinned and unetched grating regions could be used to counteract changes in the surrounding temperature.
On the other hand, a single FBG with an asymmetrical cross section can detect the degree of curvature and the bending
direction. The center reflection wavelength shifted by 0.4 nm at 1550 nm on bending that imparted a radius of curvature
of ±127 mm.
Uncertainties evaluation in optical fiber grating sensor measurements
Show abstract
This paper describes an approach to identify, quantify and express uncertainties in optical fiber grating sensor
measurements, based on the International Standard Organization's Guide to the Expression of Uncertainty in
Measurement. The proposed approach was used to evaluate the uncertainties in the measurements performed with both a
fiber Bragg temperature sensor and a long period grating refractometric sensor.
Strain sensing using long period gratings in microstructured polymer optical fibres
Richard Lwin,
Alexander Argyros,
Sergio G. Leon-Saval,
et al.
Show abstract
We investigate the use of long period gratings inscribed in single-mode microstructured polymer optical fibres for strain
sensing. A simple inscription technique allows gratings to be inscribed with features at visible wavelengths, matching
the transmission window of PMMA. Tracking of the grating features allows strains from 0.05% to over 20% to be
detected, and the inscription of multiple gratings in the same fibre at different wavelengths allows for the possibility of
distributed sensing.
Fabrication and simulation of corrugated long period microfiber gratings
Show abstract
A corrugated long period microfiber grating (C-LPMFG) is fabricated by etching the corrugated LPFG down to tens of
micrometers in diameter with corrugated periodic structures made by using imprint lithography. It can be a grating
because of the periodic effective index difference caused by the corrugated structures without prestrain. During etching
of C-LPMFGs the in-situ monitoring of resonant wavelength shows that the wavelength shift varies rapidly with the
etching of fiber. The resonant dips are calculated and have similar trends compared with the experiment data. The
C-LPMFG is used as a temperature sensor with sensitivity of -146 pm/°C.
Pressure and temperature discrimination based on dual-FBG written in microstructured fiber and standard fiber
Show abstract
We experimentally demonstrate a novel fiber-optic pressure and temperature sensor using dual-FBG written in grapefruit
microstructured fiber (GMF) and standard single-mode fiber (SMF). The pressure sensitivity of FBG in GMF is much
larger than that of SMF because the large air holes in the cross section of GMF make it experience larger axial strain than
SMF in the presence of hydrostatic pressure. While the temperature responses of the two FBGs are almost the same due
to the similar material composition in the fiber cores. Hence, pressure and temperature can be simultaneously
determined.
Compact fiber bending sensor based on superimposed gratings
Show abstract
This work has presented a compact fiber bending sensor by superimposing a uniform fiber Bragg grating (FBG) in a
tilted fiber Bragg grating (TFBG). The band of light reflected by the FBG passes through the TFBG twice and is
modulated by its transmission, which is sensitive to fiber bending. The applied bending on the sensor can be determined
by monitoring the power changes of Bragg resonance of FBG. Experimental results show the proposed sensor is
insensitive to ambient temperature changes.
Refractive index sensitivity of fibre optic long period gratings with SiO2 nanoparticle based mesoporous coatings
Show abstract
A fibre optic long period grating (LPG) with an nano-assembled mesoporous coating of alternate layers of poly
(allylamine hydrochloride) (PAH) and SiO2 nanospheres was used for the development of a fibre-optic refractometer.
PAH/SiO2 films of different thickness have been deposited onto an LPG in order to study the effect of the film thickness
on sensor performance. The device showed a sensitivity of 1927 nm/RIU over a RI range of 1.3233-1.4906.
Simultaneous measurement of strain and temperature by using micro-tapered long-period fiber gratings
Show abstract
A new fabrication of micro-tapered long-period fiber grating based on a micro-tapering technique is proposed for
simultaneous measurement of strain and temperature. The transmission characteristics of the periodically tapered
long-period fiber gratings with variations in strain and temperature are measured.
Demodulation based on a long-period grating in photonic crystal fiber with differential processing for highly birefringent fiber loop mirror temperature sensor
Show abstract
Demodulation based on a long-period grating (LPG) in a photonic crystal fiber (PCF) with differential processing
was proposed to eliminate the noise of fiber sensors and raise the accuracy of the highly-birefringent fiber loop
mirror (HiBi-FLM) temperature sensor. Utilizing the property temperature insensitive and the filtering function of
the LPG in PCF, the intensities of two signals located respectively within the positive and negative linear region of
the LPG's transmission spectrum can be monitored simultaneously and accurately. The noise of fiber sensors is
eliminated effectively by the algorithm of two signals, since the two signals (also including the noise of fiber
sensors) transmit through the same way to the monitor. Experimental results show that the proposed demodulation
eliminates not only all of power fluctuations in the system, but also raises the accuracy of the sensor. The value of
the algorithm remains constant when the power of light source varies ±10% and the relative error between the
measured temperature change and the true change is only 0.34%. Compared with the sensing without the algorithm,
the accuracy increases from~90.5% to ~99.7%.
Novel fiber loop mirror pressure sensor using a LPG as demodulation device
Yong Zhao,
Hongke Wu,
Qi Wang
Show abstract
In order to cut short the size of fiber loop mirror (FLM) sensor and eliminate the environmental temperature influence on
it, polarization-maintaining photonic crystal fiber (PM-PCF) is used in the sensor structure and introduced in this paper.
Mathematical model of external pressure and birefringence is established and shifts of FLM transmission spectrum with
different pressures are simulated. The long period fiber gating (LPG) acts as a linear optical wavelength filter which
transformed wavelength shifts to optical power, thus sensitivity of system was improved due to the demodulation result
of difference of two adjacent peaks of transmission.
Pressure sensitivity of dual resonant long-period gratings written in boron co-doped optical fiber
Show abstract
The paper presents a pressure sensor based on a long-period grating (LPG) written in boron co-doped photosensitive
fiber and operating at the phase-matching turning point. It is shown that the pressure sensitivity can be tuned by varying
the UV exposure time during the LPG fabrication process. The achieved pressure sensitivity can reach over 1 nm•bar-1,
and is at least four times higher than for previously presented gratings working away from the double-resonance regime.
In terms of intensity-based measurement, the sensitivity at the turning point can reach 0.212 dB•bar-1.
Effective tuning of long-period grating refractive-index sensitivity by plasma-deposited diamond-like carbon nano-coatings
Show abstract
This work presents an application of radio-frequency plasma-assisted chemical-vapor-deposited (RF PACVD) diamondlike
carbon (DLC) nano-coatings for effective tuning of the refractive-index (RI) sensitivity of long-period gratings
(LPGs) over a wide range (nD from 1 to 1.47). The technique allows for an efficient deposition of good quality nanofilms
as required for optical sensors. The thin overlay effectively changes the distribution of the cladding modes and thus
tunes the device's RI sensitivity. We correlated the optical properties of the DLC films with the RI sensitivity of the
LPGs. For the developed deposition process parameters, the tuning can be realized simply by varying the length of time
taken to deposit the high-refractive-index (n>2 @ λ=1460 nm) DLC film. The advantage of this approach is its speed
(the deposition process takes at most 7 minutes) and precision in determining the RI sensitivity of the LPGs.
UV inscribed long period gratings with femtosecond ablated axial fibre slots for polarization control
Show abstract
We present data on the development a new type of optical fibre polariser and the characterisation of its wavelength
properties. The device is fashioned using a two step process. Firstly, a standard UV long period grating (LPG) with a
period of 330μm is inscribed into hydrogenated SMF-28, followed by femtosecond laser ablation of a groove parallel to
the fibre axis. The UV inscribed LPGs have inherently low birefringence. However, the removal of the cladding layer
parallel to the location of the LPG within the fibre core (as a result the ablation) modifies the cladding modes that couple
with the LPG. Furthermore, the groove breaks the fibre symmetry introducing a non-uniform stress profile across the
fibre cross section leading to significant birefringence. We show that increasing the depth of the groove increases the
birefringence, and this behaviour coupled with the ability to control the wavelength location of the LPGs attenuations
peaks results in a polariser able to operate at almost any wavelength and birefringence. The maximum birefringence
reported here as polarisation mode splitting was approximately 39±0.1nm with a polarisation loss of 10dB.
Highly refractive index sensitive femtosecond laser inscribed long period gratings
Show abstract
The distinct behaviour of femtosecond laser inscribed long period gratings, with a non-uniform index perturbation within
the optical fibre core, has been studied experimentally. The non-uniform laser-induced perturbation results in light
coupling from the core mode to a greater number of cladding modes than is the case with their UV laser inscribed
counterparts, and this is made evident from the surrounding refractive index (SRI) grating response. Femtosecond
inscribed long period gratings are shown to simultaneously couple to multiple sets of cladding modes. A 400μm LPG is
shown to result in attenuation peaks that have both blue and red wavelength shifts over a 1250nm to 1700nm wavelength
range. This gives rise to SRI sensitivities far greater than anything achievable by monitoring a single attenuation peak.
The maximum sensitivity produced by monitoring a single attenuation peak was 1106nm/RIU, whereas monitoring
opposing wavelength shifts resulted in a significantly improved sensitivity of 1680nm/RIU.
Multi long-period gratings in a fiber carved and written by using a CO[sub]2[/sub] laser for distributed sensing
Yutaka Katsuyama,
Yutaka Tokunaga,
Saburo Kasahara,
et al.
Show abstract
A multi long-period grating (multi-LPG) sensor has been proposed for distributed sensing. To fabricate the
multi-LPG sensor, a carved LPG has also been proposed for easy fabrication of the multi-LPGs with different resonant
wavelengths in a similar loss spectrum. The 2-LPG sensor was fabricated in a fiber successfully, containing carved and
uncarved LPGs. The resonant wavelength shift was 64 nm by the carving. The temperature dependence of the resonant
wavelength was 0.11 nm/deg, and the temperature distributed sensing was demonstrated to be possible by the 2-LPG
sensor.
Temperature characteristics of microfiber long-period-gratings fabricated by a femtosecond infrared laser
Show abstract
Temperature characteristics of long period gratings (LPGs) in microfibers are investigated. The LPGs are formed by
periodic structural perturbation by use of a femtosecond infrared laser. The sensitivity of resonant wavelength to
temperature was measured to be around 10 pm/ºC, an order of magnitude lower than a typical LPG in conventional
single mode fiber.
Bending sensitivity of long-period fiber gratings written in polarization-maintaining fiber by CO[sub]2[/sub] laser
Show abstract
We demonstrate the unique bending characteristics of the long-period fiber gratings (LPFGs) written in a panda
polarization-maintaining (PM) fiber using CO2 laser. The bending sensitivity of the grating is not only sensitive to the
direction of the fiber bending, but also dependent on the irradiation direction of the laser writing beam with respect to the
principal axes of the PM fiber. The high sensitivity directional bending effect can be attributed to the asymmetric index
distribution of the fiber cladding induced by both stress changes in the stress-applying parts of the PM fiber and high
absorption of the CO2 laser at the exposure side, which may find promising application in fiber grating based bending
sensors.
A spectrally and spatially multiplexed LPG sensor system using an InGaAs CCD linear array
Show abstract
In this paper we report our progress on the development of a spatially and spectrally multiplexed LPG-based
fiber-optic sensor that uses an InGaAs CCD linear array and a diffraction grating for the detection of spectral
changes. Three 1x2 fiber-optical switches are used to realize a system of spatial multiplexing of four sensing
channels. Up to three LPGs can be connected in series in each channel. The end grating of each channel has a
fiber reflector spliced to it and the reflected signals are directed to the detection unit via a circulator. To test the
system bending and external refractive index changes have been traced.
Highly sensitive refractive index sensor based on two cascaded long period gratings with rotary refractive index modulation
Show abstract
We present a refractive index (RI) sensor based on a fiber Mach-Zehnder interferometer, which is realized by two
cascaded special long period gratings with rotary refractive index modulation (C-RLPFG). The wavelength shift of the
refractometer behaves good linear response in a RI range of 1.3342 to 1.3362, and the sensitivity of 14.5pm/mm for
0.01SRI change has been obtained. The sensitivity is 4 times higher than that of M-Z interferometer formed by using
normal long period fiber gratings. Such kind of high sensitivity, easy fabrication and simple structure interferometer may
find applications in chemical or biochemical sensing field.
Long period grating for acoustic wave detection
Show abstract
In this work a long period grating (LPG)-based optical fibre sensor system has been specifically
configured and set up for the acoustic wave detection. In doing so a long period grating, placed
between two pillars, is exposed to acoustic waves generated by a loudspeaker placed at a certain
distance. With the variation of the magnitude and frequency of the acoustic signal, the long period
grating-based sensor system has been observed to be sensitive to some specific frequencies,
irrespective of the intensity variation of the acoustic signals generated. Further investigation has
shown that the distance between the pillars is able to tune these specific frequency ranges, allowing for
an optimized detection using a long period grating. The positive results obtained have shown the
potential for the LPG-based technique to be used for acoustic wave detection in various media, such as
fluids, and/or solids.
Asymmetrical twin-core fiber based long period fiber gratings
Show abstract
A twin-core fiber based long period fiber grating (LPFG) has been proposed and fabricated by using CO2 laser pulses
exposure approach. It makes two long period gratings in parallel and integrates the two fiber LPFG devices in one fiber.
It could be used in biological, chemical and environmental sensing system.
Strain sensitivity of long period gratings in hollow-core photonic bandgap fibers
Show abstract
We investigate the strain sensitivity of long period gratings (LPGs) fabricated in hollow-core photonic bandgap fibers
(HC-PBFs). The LPGs are fabricated by periodically deforming the air-holes along the PBFs by use of a CO2 laser.
Resonant couplings between the LP01 and LP11 core modes results in two highly polarization-dependant loss dips in the
transmission spectrum. The sensitivity of the resonant wavelength to strain was found to vary from -1.48 to -2.4 pm/με when the grating pitch was changed from 225 to 175 μm. Theoretical investigation suggests that the size and shape of the
core can have significant influence on the strain sensitivity.
Highly sensitive operation of LPG vibration sensor using bending-induced spectral change
Show abstract
Bending-characteristics of long period fiber gratings (LPGs) are investigated for use in LPG vibration sensors based on
an intensity modulation scheme, in which a tunable laser is used for an optical source with its wavelength tuned to a
transmission spectrum curve of an attenuation dip of an LPG and the partially transmitted light through the LPG is
modulated in intensity by applied vibrations. In the experiment, LPGs are fabricated by use of an UV irradiation
technique and their bending-induced spectral changes are examined in terms of the wavelength and transmittance of the
attenuation dip. In contrast to the axial strain, it is confirmed that the much larger spectral changes are obtained when
bending deformations are applied to the LPGs. The intensity-based vibration sensor is then demonstrated by adopting
the bending effects on a LPG spectrum and its highly sensitive operation is successfully performed.
Pd-Ag film coated cascaded long period gratings for hydrogen gas sensing
Show abstract
A Mach-Zehnder-like interferometer based on cascaded long period gratings with palladium silver (Pd-Ag) film coating
is developed for monitoring the hydrogen concentration. The visibility of fringes is measured using Fourier analysis. The
basic theory was given and preliminary experiment had been proved that this sensor can used to monitor the hydrogen
concentration. The sensor showed a good response.
Simultaneous measurement of temperature, hydrostatic pressure and acoustic signal using a single distributed Bragg reflector fiber laser
Show abstract
A fiber-optic sensor based on a dual polarization fiber grating laser for simultaneous measurement of temperature,
hydrostatic pressure and acoustic signal is proposed and experimentally demonstrated. The acoustic wave induces a
frequency modulation (FM) of the carrier in radio frequency (RF) range generated by the fiber laser and can be easily
extracted by using the FM demodulation technique. The temperature can be determined by the laser wavelength. The
hydrostatic pressure can be determined by monitoring the static shift of the carrier frequency and deducting the effect of
the temperature.
Sensor Characterization
High-birefringent fiber loop mirror with an output port probe for sensing applications
Show abstract
Two new configurations of high-birefringent fiber loop mirror with an output port probe are proposed. The two
configurations used two couplers spliced between them with unbalanced arms and one output port is used as the probe
sensor. The difference between them is that the section length of high-birefringent fiber is located between the two
couplers (first configuration) or spliced in the output port probe (second configuration). The first new configuration is
studied as an optical refractometer and the second configuration is analyzed when the strain and temperature are applied.
Distributed optical fiber temperature sensor using only anti-Stokes Raman scattering light in a loop configuration
Show abstract
In this paper we demonstrate distributed Raman temperature sensing (RDTS) in a loop scheme employing anti-Stokes
light intensity only. Using a single-channel receiver and anti-Stokes traces measured in loop configuration, we
implement RDTS with inherent compensation of fiber wavelength-dependent losses, as well as local external
perturbations. Experimental results show a signal-to-noise ratio enhancement with respect to a standard RDTS in loop
configuration, providing a robust and reliable high-performance sensor for long sensing ranges.
Impact of Raman scattering and modulation instability on the performances of Brillouin sensors
Show abstract
The impact of Raman scattering and modulation instability is studied in Brillouin time-domain analysis systems. It turns
out to be very detrimental for long-range sensing as a result of the extended interaction length combined to the high
pump peak pulse power. The conditions under which these effects limit the sensing range are determined and the
modeling is very well confirmed by experimental results.
Fiber-optic ultrasonic probe based on refractive-index modulation in water
Show abstract
We report on the measurement of sound pressure in water utilizing the modulation of the optical reflectivity at the end of
an optical fiber. First, we develop a new experimental setup comprising a low-coherent light source to suppress the
interference noise. Then, we formulate the relation between the sound pressure and the modulation in the reflected light
intensity, and theoretically analyze the performance of this method with emphasis on the directivity and the sensitivity.
Post Deadline Paper Session
High-repetition-rate distributed Brillouin sensor by correlation domain analysis with differential frequency modulation
Show abstract
A novel kind of high repetition-rate distributed Brillouin sensor is proposed and
experimentally demonstrated based on optical correlation-domain analysis with differential
frequency modulation, where the optical frequencies of the pump and the probe waves are
modulated at slightly different RF frequencies so that the temporal position of the
measurement is continuously and repeatedly swept along a fiber under test. A distribution
map of Brillouin frequency variation along a 100 m optical fiber is acquired at a repetition
rate of 20 Hz with an accuracy of ± 2.5 MHz and a spatial resolution of about 80 cm.
Near shot-noise limited performance of an open loop laser-driven interferometric fiber optic gyroscope
Show abstract
We report for the first time experimental evidence of near shot-noise limited performance for an open loop
interferometric fiber optic gyroscope interrogated with a narrowband laser instead of a broadband source. Using a highly
coherent laser source (▵f = 2.2 kHz), the measured gyroscope noise is 350 nrad/Hz for an average returning power of
20 μW, while the measured noise for the same gyro operated with a broadband source (▵λ ≈ 30 nm) was 850 nrad/√Hz.
This measured noise is only ~2 dB above the calculated shot noise for this power. This result was made possible by using
a very narrow linewidth, which greatly reduces the laser phase noise and thus the phase-noise-mitigated coherent
backscattering. This excellent noise performance has applications for future fiber gyroscope technologies as well as other
sensors utilizing a Sagnac interferometer. The bias drift of the laser-driven gyroscope was higher than anticipated but
could be reduced to roughly Earth-rate using a frequency sweeping technique. In addition to improved sensitivity, the
benefits of using a laser include much higher scale factor stability, lower power consumption, and lower component cost.
Multiplexed interferometric displacement sensing below the laser frequency noise limit
Show abstract
The resolution of fiber optic interferometry sensors is often limited by frequency noise in the laser. For this reason, prestabilization
techniques have been used to reduce laser frequency fluctuations and improve signal resolution. However,
for multi-element systems this becomes cumbersome and difficult to implement. In this paper, we demonstrate the use of
digitally-enhanced interferometry for the interrogation of a multi-element sensing system. Over 50 dB of cross-talk
rejection was found, with displacement resolutions of ~ 100 pm. Furthermore, using this technique, sub-frequency noise
displacement resolution was obtained without the need for high performance sensors.
Depletion in a distributed Brillouin fiber sensor: practical limitation and strategy to avoid it
Show abstract
Energy transfer between the interacting waves in a distributed Brillouin sensor can result in a distorted measurement of
the local Brillouin gain spectrum, leading to systematic error. We demonstrate here that this behavior can be fully and
precisely modeled, and an excellent quantitative agreement is found with experimental tests. Strict guidelines can be
enunciated from this description to make the impact of depletion negligible, for any type and any length of fiber.
Distributed fiber beat length, birefringence and differential group delay measurement using BOTDA technique
Show abstract
A novel method for distributed fiber beat length, birefringence and differential group delay (DGD) measurement based
on Brillouin optical time domain analysis (BOTDA) technique is proposed. The difference of local maximum and
minimum Brillouin gain is determined by scanning input state of polarization (SOP) of pulsed probe wave to recover
local beat length. The average beat length, birefringence and DGD measured on 100m SMF28 at 1550nm wavelength
with 1m spatial resolution is 11.8m, 1.4×10-7 and 0.21ps respectively.
An all polymer fibre optic sensor for measuring rapid change in oxygen partial pressure
Show abstract
A reliable, robust and low cost fibre optic oxygen sensor for measuring rapid changes in oxygen partial pressure has been
developed using a polymer optical fibre and a polymer sensing matrix which is biocompatible with human tissue. These
materials have been used in many medical and biomedical applications. The polymer fibre optic oxygen sensor is based
on the fluorescence quenching of a fluorophore by oxygen. The sensing matrix, containing immobilized Pt(II) complexes,
was coated at the end of the polymer optical fibre. The sensitivity and time response of the sensor were evaluated using
the method of luminescence intensity measurement. The polymer substrate influence on the sensor time response was
reduced by using a fibre taper design, and the response time of the optimized sensor was less than 200ms. This all
polymer fibre optic oxygen sensor is more suitable for clinical use in terms of safety, robustness, flexibility, and low
cost.
High-axial-resolution distributed lateral displacement measurement based on differential pulse-width pair BOTDA
Show abstract
We report for the first time to the best of our knowledge a distributed lateral displacement sensor through measuring
high-spatial-resolution axial strain based on differential pulse-width pair Brillouin optical time-domain analysis. With the
assumption of a sine-shape displacement caused by a small surface deformation, the relationship between the axial strain
and the lateral displacement of a flat plate is established, based on which a distributed lateral displacement measurement
is realized. In experiment, a periodic lateral displacement of a flat plate is constructed through a ripple spring by
applying side pressure on them, and the axial strain measurement with a 2-cm spatial resolution is performed by using a
differential pulse pair of 8/8.2 ns. Using two types of ripple springs, measurements of lateral displacements with periods
of 30 and 32.5 mm are demonstrated with a maximum displacement of 0.43 mm and a minimum measurable
displacement of ~40 μm.