Chirped-pulse phase-sensitive reflectometry: hearing behind the walls with high fidelity
Author(s):
M. Gonzalez-Herraez;
J. Pastor-Graells;
A. García-Ruiz;
M. R. R. Fernández-Ruiz;
H. F. Martins;
S. Martin-Lopez
Show Abstract
We review our recent work on chirped-pulse phase-sensitive optical time-domain reflectometry along optical fibers and its application in the measurement of true nanostrain variations in the kHz frequency range over km-long fibers. We also show how this technique can be used to perform distributed photothermal measurements of gas presence in suitable microstructured fibers
Numerical modelling of distributed vibration sensor based on phase-sensitive OTDR
Author(s):
A. Masoudi;
T. P. Newson
Show Abstract
A Distributed Vibration Sensor Based on Phase-Sensitive OTDR is numerically modeled. The advantage of modeling the building blocks of the sensor individually and combining the blocks to analyse the behavior of the sensing system is discussed. It is shown that the numerical model can accurately imitate the response of the experimental setup to dynamic perturbations a signal processing procedure similar to that used to extract the phase information from sensing setup.
Simplified and fast acquirable BOTDA with frequency-swept probe pulse
Author(s):
Chihiro Kito;
Hiroshi Takahashi;
Kunihiro Toge;
Tetsuya Manabe
Show Abstract
We propose a novel BOTDA that can measure a BFS change appearing on a time axis with a single-shot measurement by using a frequency-swept probe pulse. The proposed method employs a very simple laser control and detection system, without precise test light frequency control, and with an oscilloscope. We demonstrate a fast BFS distribution measurement completed within 0.33 s with 1.8 MHz BFS accuracy for a 10 km range, and discuss its advantages compared with conventional BOTDA.
Long period fiber gratings for bio-sensing: an improved design methodology
Author(s):
Somnath Bandyopadhyay;
Ignacio Del Villar;
Sankhyabrata Bandyopadhyay;
Palas Biswas;
Nandini Basumallick;
Tanoy Kumar Dey
Show Abstract
Long period fiber grating (LPFG) has been actively researched in bio-sensing applications owing to its ability to sense refractive index (RI) of the surrounding medium. We investigate on the adequacy of the present state of the art to quantify adsorption of bio-molecules on the surface of the fiber confined within few tens of nanometers and possible improvements in the design of sensors suitable for bio-sensing applications.
Nano-structured optical fiber bundles for remote SPR detection: a first step toward in vivo biomolecular analysis
Author(s):
Karim Vindas;
Elodie Engel;
Patrick Garrigue;
Thierry Livache;
Stéphane Arbault;
Neso Sojic;
Loic Leroy
Show Abstract
This work presents the proof of concept of the detection of global and surface optical index variations by surface plasmon resonance (SPR) thanks to optical fiber bundles. This work is the first necessary step for the future design of a lab-on-fiber tool dedicated to molecular analysis for endoscopic diagnosis. Our approach is based on nanostructured optical fiber bundles comprising several thousands of individual optical fibers. These nanostructures were coated by a thin gold layer in order to gain interesting optical properties such like SPR. The sensitivity and resolution of the bundle to global optical index changes were measured in retro-reflection. We performed numerical simulations in order to optimize the fiber tip geometry, gold coating thickness and finally enhance their analytical performances. We achieved a resolution of 10-4 refractive index unit, which is fully compatible with the detection of biological interactions involving large proteins or bacteria. Finally, we proved that our sensor was sensitive to surface optical index variations and able to detect the adsorption of a thin self-assembled molecular layer.
Multi-parameter fiber optic sensors based on fiber random grating
Author(s):
Yanping Xu;
Mingjiang Zhang;
Ping Lu;
Stephen Mihailov;
Xiaoyi Bao
Show Abstract
Two novel configurations of multi-parameter fiber-optic sensing systems based on the fiber random grating are reported. The fiber random grating is fabricated through femtosecond laser induced refractive index modification over a 10cm standard telecom single mode fiber. In one configuration, the reflective spectrum of the fiber random grating is directly detected and a wavelength-division spectral cross-correlation algorithm is adopted to extract the spectral shifts for simultaneous measurement of temperature, axial strain, and surrounding refractive index. In the other configuration, a random fiber ring laser is constructed by incorporating the random feedback from the random grating. Numerous polarization-dependent spectral filters are formed along the random grating and superimposed to provide multiple lasing lines with high signal-to-noise ratio up to 40dB, which enables a high-fidelity multi-parameter sensing scheme by monitoring the spectral shifts of the lasing lines. Without the need of phase mask for fabrication and with the high physical strength, the random grating based sensors are much simpler and more compact, which could be potentially an excellent alternative for liquid medical sample sensing in biomedical and biochemical applications.
Magnetic field sensor based on multi-port microcoil resonator
Author(s):
W. Talataisong;
R. Ismaeel;
A. Masoudi;
M. Beresna;
G. Brambilla
Show Abstract
A multi-port microcoil resonator magnetic field sensor based on a microfiber coupler coil resonator (MMCR) is presented. The microfiber coupler coil is fabricated by coiling a four-port microfiber coupler with a uniform waist region around a low index support rod. The MMCR is embedded in a low refractive index polymer to increase the robustness and operation stability. The enhanced sensor response to the magnetic field is ascribed to the diverse MMCR response to the light polarization state. The MMCR magnetic field sensor is compact and low cost, and exhibits a magnetic field sensitivity of 37.09 dB/T with an estimated minimum detection limit (DL) of ~ 27 μT.
High finesse hollow-core fiber resonating cavity for high sensitivity gas sensing application
Author(s):
Yanzhen Tan;
Wei Jin;
Fan Yang;
Hoi Lut Ho
Show Abstract
We present all-fiber resonating Fabry-Perot gas cells made with a piece of hollow-core photonic bandgap fiber (HCPBF) sandwiched by two single mode fibers with mirrored ends. A HC-PBF cavity made of 6.75-cm-long HC-1550-06 fiber achieved a cavity finesse of 128, corresponding to an effective optical path length of 5.5 m. Such HC-PBF cavities can be used as absorption cells for high sensitivity gas detection with fast response. Preliminary experiment with a 9.4-cm-long resonating gas cell with a finesse of 68 demonstrated a detection limit better than 7.5 p.p.m. acetylene.
Compact multichannel MEMS based spectrometer for FBG sensing
Author(s):
D. Ganziy;
B. Rose;
O. Bang
Show Abstract
We propose a novel type of compact multichannel MEMS based spectrometer, where we replace the linear detector with a Digital Micromirror Device (DMD). The DMD is typically cheaper and has better pixel sampling than an InGaAs detector used in the 1550 nm range, which leads to cost reduction and better performance. Moreover, the DMD is a 2D array, which means that multichannel systems can be implemented without any additional optical components in the spectrometer. This makes the proposed interrogator highly cost-effective. The digital nature of the DMD also provides opportunities for advanced programmable spectroscopy.
Compact relative humidity sensor based on an Agarose hydrogel coated silica microsphere resonator
Author(s):
Arun Kumar Mallik;
Dejun Liu;
Vishnu Kavungal;
Xiaokang Lian;
Gerald Farrell;
Qiang Wu;
Yuliya Semenova
Show Abstract
In this paper, we propose a novel approach to measurements of low relative humidity (RH) levels based on the whispering gallery modes (WGMs) phenomenon in a silica microsphere resonator coated with Agarose. The spectral dips of the WGM resonances excited in the proposed sensor depend strongly on the changes in the refractive index (RI) of the coating material as well as the surrounding RI. A study of the humidity-induced RI changes in a thin Agarose layer, applied to the surface of a 162 μm-diameter silica microsphere was carried out by correlating the experimental results and numerical simulations performed using the perturbation theory. We experimentally demonstrate a linear sensing characteristic in a low-humidity range from 10% to 45% RH. The estimated quality factor of the micro-resonator is 2.82×106 and detection limit for the sensor is 0.057 %RH, corresponding to the RI resolution of 8.4×10-7 RIU.
Fiber Bragg grating sensor interrogators on chip: challenges and opportunities
Author(s):
Yisbel Marin;
Tiziano Nannipieri;
Claudio J. Oton;
Fabrizio Di Pasquale
Show Abstract
In this paper we present an overview of the current efforts towards integration of Fiber Bragg Grating (FBG) sensor interrogators. Different photonic integration platforms will be discussed, including monolithic planar lightwave circuit technology, silicon on insulator (SOI), indium phosphide (InP) and gallium arsenide (GaAs) material platforms. Also various possible techniques for wavelength metering and methods for FBG multiplexing will be discussed and compared in terms of resolution, dynamic performance, multiplexing capabilities and reliability. The use of linear filters, array waveguide gratings (AWG) as multiple linear filters and AWG based centroid signal processing techniques will be addressed as well as interrogation techniques based on tunable micro-ring resonators and Mach-Zehnder interferometers (MZI) for phase sensitive detection. The paper will also discuss the challenges and perspectives of photonic integration to address the increasing requirements of several industrial applications.
Mechanisms of signal coupling to optical fiber for FBG sensor detection of Lamb waves
Author(s):
Junghyun Wee;
Drew Hackney;
Philip Bradford;
Kara Peters
Show Abstract
One of the major challenges when using fiber Bragg grating sensors (FBGs) to detect Lamb wave or acoustic emission signals in structures is the low sensitivity of these sensors to surface waves propagating in the structure. The authors have previously demonstrated that remote bonding of the optical fiber away from the FBG can increase the measured signal amplitude. In this paper we investigate the potential mechanisms for this increase through finite element simulations and demonstrate that the shear lag effect through the adhesive is the major source of the signal amplitude difference between the direct and remote bonding cases.
Photodetector with photothermal cascaded Fabry-Perot etalons
Author(s):
George Y. Chen;
Xuan Wu;
Xiaokong Liu;
David G. Lancaster;
Tanya M. Monro;
Haolan Xu
Show Abstract
A new type of photodetector with an optical sensor is presented, which enables it to operate even in the presence of strong electro-magnetic interference. The optical sensor head consists of cascaded Fabry-Perot etalons coated with a new type of photo-thermal coating comprising of hydrogel-embedded copper-oxide micro-particles. For white-light irradiation, the photodetector exhibits a power sensitivity of 760 pm/mW, a detection limit of 16.4 μW, and an optical damage threshold of ∼100 mW or ∼800 mW/cm2. The response and recovery times are 3.0 s (∼90% of change within 100 ms) and 16.0 s.
Characterization of bovine cartilage by fiber Bragg grating-based stress relaxation measurements
Author(s):
V. Baier;
G. Marchi;
P. Foehr;
R. Burgkart;
J. Roths
Show Abstract
A fiber-based device for testing mechanical properties of cartilage is presented within this study. The measurement principle is based on stepwise indentation into the tissue and observing of corresponding relaxation of the stress. The indenter tip is constituted of a cleaved optical fiber that includes a fiber Bragg grating which is used as the force sensor. Stress relaxation measurements at 25 different positions on a healthy bovine cartilage sample were performed to assess the behavior of healthy cartilage. For each indentation step a good agreement was found with a viscoelastic model that included two time constants. The model parameters showed low variability and a clear dependence with indentation depth. The parameters can be used as reference values for discriminating healthy and degenerated cartilage.
Distributed acoustic sensing: how to make the best out of the Rayleigh-backscattered energy?
Author(s):
A. Eyal;
H. Gabai;
I. Shpatz
Show Abstract
Coherent fading noise (also known as speckle noise) affects the SNR and sensitivity of Distributed Acoustic Sensing (DAS) systems and makes them random processes of position and time. As in speckle noise, the statistical distribution of DAS SNR is particularly wide and its standard deviation (STD) roughly equals its mean (σSNR/⟨SNR⟩ ≈ 0.89). Trading resolution for SNR may improve the mean SNR but not necessarily narrow its distribution. Here a new approach to achieve both SNR improvement (by sacrificing resolution) and narrowing of the distribution is introduced. The method is based on acquiring high resolution complex backscatter profiles of the sensing fiber, using them to compute complex power profiles of the fiber which retain phase variation information and filtering of the power profiles. The approach is tested via a computer simulation and demonstrates distribution narrowing up to σSNR/⟨SNR⟩ < 0.2.
Condition monitoring of industrial infrastructures using distributed fibre optic acoustic sensors
Author(s):
Konstantin Hicke;
Maria-Teresa Hussels;
René Eisermann;
Sebastian Chruscicki;
Katerina Krebber
Show Abstract
Distributed fibre optic acoustic sensing (DAS) can serve as an excellent tool for real-time condition monitoring of a variety of industrial and civil infrastructures. In this paper, we portray a subset of our current research activities investigating the usability of DAS based on coherent optical time-domain reflectometry (C-OTDR) for innovative and demanding condition monitoring applications. Specifically, our application-oriented research presented here aims at acoustic and vibrational condition monitoring of pipelines and piping systems, of rollers in industrial heavy-duty conveyor belt systems and of extensive submarine power cable installations, respectively.
Image and video denoising for distributed optical fibre sensors
Author(s):
Marcelo A. Soto;
Jaime A. Ramírez;
Luc Thévenaz
Show Abstract
A technique based on a multi-dimensional signal processing approach is here described for performance enhancement of distributed optical fibre sensors. In particular, the main features of linear and nonlinear image denoising techniques are described for signal-to-noise ratio enhancement in Brillouin optical time-domain analysers. Experimental results demonstrate the possibility to enhance the performance of distributed Brillouin sensors by more than 13 dB using a nonlinear image denoising approach, while more than 20 dB enhancement can be obtained with video denoising.
New improvements for Brillouin optical time-domain reflectometry
Author(s):
Sébastien Le Floch;
Florian Sauser
Show Abstract
This paper presents new techniques designed to improve the performances of a BOTDR. The first one introduces a second pump to the sensor, thus doubling the Brillouin signal on the receiver. The second one uses image processing with a two-dimensional Gaussian filter whose parameters are defined. The last technique explores the possibilities offered by colour codes. The benefits of each, in terms of signal-to-noise ratio, is presented by comparing measurements over a distance range of 50km with a spatial resolution of 5m. These techniques can easily be combined and the global improvement is estimated at 10dB, compared to conventional sensors.
Characterization of depolarized GAWBS for optomechanical sensing of liquids outside standard fibers
Author(s):
Neisei Hayashi;
Yosuke Mizuno;
Kentaro Nakamura;
Sze Yun Set;
Shinji Yamashita
Show Abstract
We report an experimental study on the spectral dependence of depolarized guided acoustic-wave Brillouin scattering (GAWBS) in a silica single-mode fiber (SMF) on acoustic impedance of external materials. The GAWBS spectrum was measured when the acoustic impedance was changed from 1.51 to 2.35 kg/s⋅mm2. With increasing acoustic impedance, the linewidth increased; the dependence was almost linear in the range up to ∼2.0 kg/s⋅mm2 with an acoustic impedance dependence coefficient of 0.16 MHz/kg/s⋅mm2, which is directly applicable to acoustic impedance sensing. Meanwhile, with increasing acoustic impedance, the central frequency nonlinearly decreased, which probably originates from the change in the effective outer diameter of the silica SMF.
Discrimination of temperature and strain by combined refractive index and birefringence measurements using coherent Rayleigh sensing
Author(s):
Xin Lu;
Marcelo A. Soto;
Luc Thévenaz
Show Abstract
Temperature and strain discrimination is experimentally demonstrated in an elliptical-core polarization-maintaining fiber by making use of Rayleigh-based distributed birefringence measurements and the frequency shift of the correlation peak obtained by standard coherent optical time-domain reflectometry. The high sensitivity of coherent Rayleigh sensing and the very distinct behavior of birefringence makes the two quantities clearly discriminated, resulting in temperature and strain accuracies of ~ 40 mK and ~ 0.5 με, respectively, for distributed measurements with a 2 m spatial resolution.
Pulse compression phase sensitive optical time domain reflectometer with sub-meter resolution
Author(s):
Bin Lu;
Zhaoyong Wang;
Hanrong Zheng;
Qing Ye;
Ronghui Qu;
Howell Zhao;
Haiwen Cai
Show Abstract
We propose and experimentally demonstrate a pulse compression phase sensitive optical time domain reflectometer (φ- OTDR) with sub-meter resolution. Principle and theoretical analysis on the spatial resolution, the feasibility to obtain the phase information are provided. This technique can break the tradeoff between spatial resolution and measurement range in the traditional φ-OTDR. As example, our verifying experiment achieves 30cm spatial resolution and 20km measurement range, and the signal to noise ratio (SNR) reaches 10dB. To our knowledge, this is the first time that such a high spatial resolution over such a long sensing range is reported in φ-OTDR-based distributed vibration sensing.
Fast Sinusoidal Frequency Scan OFDR for Long Distance Distributed Acoustic Sensing
Author(s):
Lihi Shiloh;
Avishay Eyal
Show Abstract
Implementation of Optical Frequency Domain Reflectometry (OFDR) requires a source whose instantaneous frequency can be accurately scanned over a sufficiently wide frequency range. Achieving high repetition rates of accurate linear frequency sweeps can be rather challenging. In contrast, fast and accurate Sinusoidal Frequency Scan (SFS-OFDR) can be easily implemented via direct or external optical frequency modulation. While enabling high spatial resolution measurements of a sensing fiber at high scan rates, SFS-OFDR requires a special processing algorithm to convert the detector output to fiber profiles. Previous implementation of the algorithm involved O(N2) complexity and prohibited real time operation. In this work a novel algorithm for processing SFS-OFDR raw data is introduced. Based on two consecutive FFT operations, the algorithm produces the fiber profile with O(NlogN) operations and lends itself for real time applications. The new method was tested via simulation and experiment. It enabled static detection with high resolution (~3m) at 64km and highly sensitive dynamic detection (stretching amplitude of 70nm) near the end of a 64km sensing fiber with spatial resolution <10m and with 400Hz scan repetition rate.
Brillouin optical time-domain analyzer for extended sensing range using probe dithering and cyclic coding
Author(s):
Haritz Iribas;
Alayn Loayssa;
Florian Sauser;
Miguel Llera;
Sébastien Le Floch
Show Abstract
We present an enhanced performance Brillouin optical time-domain analysis sensor that uses dual probes waves with optical frequency modulation and cyclic coding. The frequency modulation serves to increase the probe power that can be injected in the fiber before the onset of non-local effects and noise generated by spontaneous Brillouin scattering. This leads to higher detected signal-to-noise ratio (SNR), which is further increased by the coding gain. The enhanced SNR translates to extended range for the sensor, with experiments demonstrating 1-m spatial resolution over a 164 km fiber loop with a 3-MHz Brillouin frequency shift measurement precision at the worst contrast position. In addition, we introduce a study of the power limits that can be injected in the fiber with cyclic coding before the appearance of distortions in the decoded signal.
20 dB SNR enhancement in phase-sensitive OTDR using pulse stretching and recompression
Author(s):
Juan Pastor-Graells;
Luis Romero Cortés;
Hugo F. Martins;
María R. Fernández-Ruiz;
José Azaña;
Sonia Martin-Lopez;
Miguel Gonzalez-Herraez
Show Abstract
This work shows the possibility of using chirped pulse amplification concepts in order to increase the signal-to-noise ratio (SNR) of phase sensitive optical time domain reflectometry (ΦOTDR) sensors. This method allows to increase the SNR of a ΦOTDR sensor without sacrificing spatial resolution. Here, we report a ΦOTDR sensor with a spatial resolution of 3 mm (limited only by the available detection equipment) and an SNR increase of 20 dB over the traditional architecture. To our knowledge, this is the highest-resolution ΦOTDR sensor reported to date.
OTDR based on Brillouin dynamic grating in an e-core two-mode fiber for simultaneous measurement of strain and temperature distribution
Author(s):
Yong Hyun Kim;
Kwang Yong Song
Show Abstract
Discriminative measurement of strain and temperature distribution is experimentally demonstrated by optical time-domain reflectometry of Brillouin dynamic grating (BDG-OTDR) in an elliptical core two-mode fiber (e-core TMF). The acoustic waves generated by the amplified spontaneous Brillouin scattering of LP01 mode in x-polarization are used to reflect the LP11 mode in x- and y-polarizations. Distribution maps of intermodal birefringence between the LP01 and LP11 modes with two different polarizations are measured to separate strain and temperature induced spectral shift of the BDG in a 95 m ecore TMF with 2.0 m spatial resolution. The strain and temperature sensitivities are measured to be ‒0.082 MHz/με and 6.8 MHz/°C for the pair of LP01 y-LP11 x modes, and ‒0.095 MHz/με and 3.9 MHz/°C for the pair of LP01 x-LP11 x modes, respectively.
Towards ultra-long-distance distributed fiber optic sensing
Author(s):
Zinan Wang;
Xinhong Jia;
Huijuan Wu;
Fei Peng;
Yun Fu;
Yunjiang Rao
Show Abstract
Distributed fiber-optic sensing (DFOS) has drawn great attention in both academic research and industrial applications due to its unique advantages. Recent progress at University of Electronic Science and Technology of China (UESTC) in DFOS, mainly on ultra-long-distance Brillouin optical time-domain analysis (BOTDA) and phase-sensitive optical timedomain reflectometry (Φ-OTDR), is discussed in this paper, including research progress and real-life applications.
Integration of fiber-tip cavities in single-ion traps for quantum sensing
Author(s):
Peter Horak;
Nina Podoliak;
Hiroki Takahashi;
Matthias Keller
Show Abstract
We investigate geometries for efficient coupling of single ions to fiber-coupled light fields for applications in quantum sensing, quantum metrology, and quantum information processing. Specifically, we discuss the integration of fiber-tip microcavities into radio-frequency ion traps. The distortions of the trapping fields induced by the presence of the optical fibers are simulated for a range of ion trap geometries and the most promising arrangements are identified. Finally, we investigate the use of fiber-tip microcavities with non-spherical mirrors for enhanced ion-light coupling at the center of the trap by appropriate shaping of the cavity modes.
Coherent Pound-Drever-Hall technique for high resolution fiber optic strain sensor at very low light power
Author(s):
Mengxin Wu;
Qingwen Liu;
Jiageng Chen;
Zuyuan He
Show Abstract
Pound-Drever-Hall (PDH) technique has been widely adopted for ultrahigh resolution fiber-optic sensors, but its performance degenerates seriously as the light power drops. To solve this problem, we developed a coherent PDH technique for weak optical signal detection, with which the signal-to-noise ratio (SNR) of demodulated PDH signal is dramatically improved. In the demonstrational experiments, a high resolution fiber-optic sensor using the proposed technique is realized, and n"-order strain resolution at a low light power down to -43 dBm is achieved, which is about 15 dB lower compared with classical PDH technique. The proposed coherent PDH technique has great potentials in longer distance and larger scale sensor networks.
Photonic sensors: from horse racing to horse power
Author(s):
Cicero Martelli;
Jean Carlos Cardozo da Silva;
Daniel Pipa;
Marco José da Silva;
Carlos R. Zamarreño;
John Canning;
Pedro E. Schaphauser;
Guilherme Dutra;
Rafael Daciuk;
José R. Galvão;
Felipe Mezzadri;
Andre B. Renzo;
Uilian Dreyer;
Guilherme Weber;
Cesar Janeczko;
Otoniel G. da Rocha
Show Abstract
The use of photonic sensors to monitor horses is presented and reviewed. Results are very promising and can be used in other areas to monitor animals, machines or industrial processes.
A portable device for cancer margin assessment using a pH sensitive optical fibre probe
Author(s):
Erik P. Schartner;
Matthew R. Henderson;
Malcolm Purdey;
Tanya M. Monro;
P. Grantley Gill;
David F. Callen
Show Abstract
We report the development of an optical fibre probe which could find use as an aid for margin detection during surgery. A fluorophore doped polymer is coated on an optical fibre tip, allowing for pH values of unknown tissue to be measured and compared to healthy tissue, to discriminate between healthy and cancerous tissue.
This probe is integrated within a portable system, requiring no alignment or access to specialised vibration damped optical tables. A miniature spectrometer allows for measurements to be performed on-site, opening up the potential for use of these probes within the operating theatre for in-vivo measurements.
Biomolecular detection with an interferometric microfiber-capillary optofluidic sensor
Author(s):
Lili Liang;
Long Jin;
Bai-Ou Guan
Show Abstract
We have developed a chip-scale optofluidic sensor for biomolecular detection, by tapering laterally aligned silica microfiber and capillary to form a modal interferometer. With the pre-immobilization of DNA probes, the sensor is capable of selectively detecting single-stranded microRNA-let7a (molecular weight: 6.5 k) by measuring the spectral shift of the interferometric spectrum. A log-linear response from 2 nM to 20 μM and a minimum detectable concentration of 212 pM (1.43 ng/mL) have been achieved. The sensor is promising for future diagnosis applications due to its high sensitivity, resistance to environmental perturbations, improved portability, and intrinsic connection to fiber optic measurement.
Wide-field photoacoustic microscopy with a fiber laser ultrasound sensor
Author(s):
Yizhi Liang;
Long Jin;
Jun Ma;
Xue Bai;
Bai-Ou Guan
Show Abstract
A compact fiber grating laser has been exploited as an ultrasound sensor to probe optically induced spherical elastic waves, taking advantage of its response in beat-frequency variation of the laser output. Optical-resolution photoacoustic microscopy (PAM) is further implemented with such a sensor by raster scanning the excitation light with a 2-axis galvo scanner. A PAM image of mouse ear with a field width of 2 mm is demonstrated. The wide field-of-view of the sensor allows the implementation of fast-scanning PAMs which is attractive for in vivo imaging applications.
Enhancement of the sensitivity of ferrofluidic magneto-optical fiber sensor by non-adiabatic tapered Hi-Bi fiber in fiber loop mirror
Author(s):
Azam Layeghi;
Hamid Latifi
Show Abstract
A magnetic field fiber optic sensor based on Nano-magnetic fluid and Hi-Bi non-adiabatic tapered optical fiber in fiber loop mirror (HB-TFLM) is proposed and theoretically explained. As compared to the reported magnetic fluid (MF) based sensors, the achieved sensitivity of the proposed sensor is 255 pm/mT, which is enhanced by 3.6 times of magnitude relative to in line non-adiabatic tapered optical fiber sensor, used only 0.1% of the volume concentration of MF nanoparticles. Detection limit of the HB-TFLM to external magnetic field in range from 0 to 21 mT and 22 to 50 mT was 7.8 μT and 39.2 μT, respectively.
Specific detection of very low concentrations of DNA oligonucleotides with DNA-coated long-period grating biosensor
Author(s):
Karolina H. Czarnecka;
Magdalena Dominik;
Marta Janczuk-Richter;
Joanna Niedziółka-Jönsson;
Wojtek J. Bock;
Mateusz Śmietana
Show Abstract
Label-free biosensing using optical long-period gratings (LPGs) induced in optical fiber and coated with biological compound enables for detection and monitoring the kinetics of reactions taking places on the sensor’s surface. The labelfree detection effect for the LPG biosensor working near the dispersion turning point (DTP) of higher order cladding modes can be observed as resonance wavelength shift induced by binding of biomolecules to fiber surface. In this study we analyzed shift of the resonance wavelength for LPG after its functionalization with DNA layer and during DNA hybridization. It has seen found that the LPG is able to be functionalized with DNA oligonucleotide, acting as a probe and after the functionalization can selectively bind specific complementary DNA oligonucleotides in a very low concentration. DNA-coated LPG can be used as a probe capturing specific DNA sequences with wide ranges of concentrations from 0.1 to 10 pM. Hybridization of the DNA on the fiber surface has also been verified with Midorii Green florescent marker.
Refractive index sensing with Al2O3-nanocoated long-period gratings working at dispersion turning point: temperature cross-sensitivity
Author(s):
Mateusz Śmietana;
Magdalena Dominik;
Predrag Mikulic;
Wojtek J. Bock
Show Abstract
In this work is discussed an effect of nanocoating long-period grating (LPG) with an aluminum oxide (Al2O3) on its refractive index (RI) and temperature (T) sensitivity. For comparison two LPGs, namely one before and after the nanocoating process were optimized towards working at dispersion turning point (DTP) of higher order cladding modes. The DTP was reached with two methods, i.e., by wet etching of LPG’s cladding and by optimized deposition of Al2O3 thin overlay using atomic layer deposition (ALD) method. For both the cases we show significant increase in RI sensitivity at DTP. When Al2O3 is deposited the RI sensitivity reaches 9270 nm/RIU for traced only one resonance out of the pair and RI in range 1.33-1.34 RIU, what is over 4-fold higher than for the bare LPG. Moreover, T sensitivity for both the structures was compared and the one for Al2O3-coated sample was found to be only up to 12% higher than for the bare sample. Higher RI sensitivity and low temperature cross-sensitivity effects allow for more accurate RI measurements than in case of bare LPGs. The Al2O3-nanocoated LPGs can further find applications in label-free biosensing, due to their optimized sensitivity in RI in range close that of water.
Optical fiber sensor-based life cycling monitoring and quality assessment of carbon fiber reinforced polymer matrix composite structures
Author(s):
N. Takeda;
S. Minakuchi
Show Abstract
Optical fiber sensors are very useful to monitor the internal strain and temperature in composites during manufacturing and assembly as well as in practical operations. The authors have been using both multi-point and distributed strain monitoring techniques to characterize the internal state of composite structures. This paper reports some recent developments of life cycle monitoring and quality control of aerospace composite structures. Specifically, distributed sensing for large-scaled parts, through-thickness strain monitoring for complex-shaped parts, and direction-dependent cure shrinkage monitoring are described, highlighting wide applicability of embedded optical fiber sensors for intelligent process monitoring and quality assessment of composite parts.
Multiplexing curvature sensors using fibre segment interferometry for lateral vibration measurements
Author(s):
Thomas Kissinger;
Edmon Chehura;
Stephen W. James;
Ralph P. Tatam
Show Abstract
Dynamic fibre-optic curvature sensing is demonstrated by interrogating chains of fibre segments, separated by broadband Bragg grating reflectors, using range-resolved interferometry (RRI). Four fibre strings, containing four fibre segments each of gauge length 20 cm, are attached to the opposing sides of a support structure and the resulting differential strain measurements allow inference of lateral displacements of a cantilever test object. Dynamic tip displacement resolutions in the micrometre range at an interferometric bandwidth of 21 kHz demonstrate the suitability of this approach for highly sensitive and cost-effective fibre-optic directional vibration measurements of smart structures.
Distributed polarization sensing
Author(s):
Andrea Galtarossa;
Luca Palmieri
Show Abstract
Distributed sensing by means of polarimetric analysis of the Rayleigh scattering has been among the first distributed optical fiber sensors ever proposed. Despite offering some unique features, like distributed sensing of magnetic fields and torsion, the method has not yet achieved full commercial maturity. The talk will review the present state of art, highlighting limits and potentialities.
High finesse silica waveguide ring resonators for resonant micro-optic gyroscopes
Author(s):
Jianjie Zhang;
Hanzhao Li;
Huilian Ma;
Zhonghe Jin
Show Abstract
A high-finesse silica waveguide ring resonator (WRR) is designed and a new record is demonstrated experimentally. The finesse and the resonant depth of the silica WRR with a length of 7.9 cm and a diameter of 2.5 cm are 196.7 and 98%, respectively. In addition, the silica WRR is pigtailed with single-polarization fiber to improve the polarization extinction ratio thus to reduce the polarization error. With the application of this high-finesse and high polarization extinction ratio WRR to the resonant micro-optic gyroscope (RMOG), a bias stability of 0.004°/s was observed over a one-hour timeframe.
Whispering gallery resonators for optical sensing
Author(s):
Ramgopal Madugani;
Sho Kasumie;
Yong Yang;
Jonathan Ward;
Fuchuan Lei;
Síle Nic Chormaic
Show Abstract
In recent years, whispering gallery mode devices have extended their functionality across a number of research fields from photonics to sensing applications. Here, we will discuss environmental sensing applications, such as pressure, flow, and temperature using ultrahigh Q-factor microspheres fabricated from ultrathin optical fiber and microbubbles fabricated from pretapered glass capillary. We will discuss device fabrication and the different types of sensing that can be pursued using such systems. Finally, we will introduce the concept of using cavity ring-up spectroscopy to perform dispersive transient sensing, whereby a perturbation to the environment leads to a frequency mode shift, and dissipative transient sensing, which can lead to broadening of the mode, in a whispering gallery mode resonator.
Novel optical fibers for distributed sensor applications
Author(s):
Ming-Jun Li;
Shenping Li;
Jeffery S. Stone
Show Abstract
We present novel optical fiber designs to improve performance of distributed optical fiber sensors based on Rayleigh and Brillouin scatterings, including hybrid core fiber for increasing Rayleigh backscattered signal, dual core fiber for simultaneous measurement of temperature and stain, few mode fiber for enhancing sensitivity and spatial resolution and Brillouin frequency managed fiber for increasing sensing range.
Plastic optical fiber fuse and its impact on sensing applications
Author(s):
Yosuke Mizuno;
Heeyoung Lee;
Neisei Hayashi;
Kentaro Nakamura;
Shin-ichi Todoroki
Show Abstract
We review the unique properties of a so-called optical fiber fuse phenomenon in plastic optical fibers (POFs), including its slow propagation velocity (1–2 orders of magnitude slower than that in silica fibers) and threshold power density (1/180 of the value for silica fibers). We also show that an oscillatory continuous curve instead of periodic voids is formed after the passage of the fuse, and that the bright spot is not a plasma but an optical discharge, the temperature of which is ~3600 K. We then discuss its impact on distributed Brillouin sensing based on POFs.
Towards a new generation of fibre optic chemical sensors based on spider silk threads
Author(s):
Kenny Hey Tow;
Desmond M. Chow;
Fritz Vollrath;
Isabelle Dicaire;
Tom Gheysens;
Luc Thévenaz
Show Abstract
A spider uses up to seven different types of silk, all having specific functions, to build its web. For scientists, native silk - directly extracted from spiders - is a tough, biodegradable and biocompatible thread used mainly for tissue engineering and textile applications. Blessed with outstanding optical properties, this protein strand can also be used as an optical fibre and is, moreover, intrinsically sensitive to chemical compounds. In this communication, a pioneering proof-of-concept experiment using spider silk, in its pristine condition, as a new type of fibre-optic relative humidity sensor will be demonstrated and its potential for future applications discussed.
Interrogation system with auto-calibration for fiber Bragg grating sensors using VCSEL based optical frequency comb generators
Author(s):
D. A. Poiana;
J. A. Garcia-Souto;
J. E. Posada-Román;
P. Acedo
Show Abstract
A new instrumentation system for FBG interrogation is proposed. It combines the use of a VCSEL as a tunable laser and an optical frequency comb generator as a selective broadband source. Features such as auto-calibration and wave-length tracking are provided with this interrogation system. First a fast sweep searches for the FBG spectral position, its reflection profile and finds the best set of operating points for the optical comb. Then, the VCSEL is tuned with the FBG through a feedback loop to withstand large-range slow changes (strain and temperature) and, at the same time, the faster phenomena (vibrations and ultrasounds) are measured by the optical frequency comb generator. In practice, a dual comb is proposed to interrogate actively the FBG reflection in order to obtain radio frequency signals that contain the FBG dynamic-strain due to applied vibrations.
Optical fibre sensing: a solution for industry
Author(s):
T. Sun;
M. Fabian;
Y. Chen;
M. Vidakovic;
S. Javdani;
K. T. V. Grattan;
J. Carlton;
C. Gerada;
L. Brun
Show Abstract
Optical fibres have been explored widely for their sensing capability to meet increasing industrial needs, building on their success in telecommunications. This paper provides a review of research activities at City University of London in response to industrial challenges through the development of a range of fibre Bragg grating (FBG)-based sensors for transportation structural monitoring. For marine propellers, arrays of FBGs mapped onto the surface of propeller blades allow for capturing vibrational modes, with reference to simulation data. The research funded by EU Cleansky programme enables the development of self-sensing electric motor drives to support ‘More Electric Aircraft’ concept. The partnership with Faiveley Brecknell Willis in the UK enables the integration of FBG sensors into the railway current-collecting pantographs for real-time condition monitoring when they are operating under 25kV conditions.
Multi-parameter monitoring of electrical machines using integrated fibre Bragg gratings
Author(s):
Matthias Fabian;
David Hind;
Chris Gerada;
Tong Sun;
Kenneth T. V. Grattan
Show Abstract
In this paper a sensor system for multi-parameter electrical machine condition monitoring is reported. The proposed FBG-based system allows for the simultaneous monitoring of machine vibration, rotor speed and position, torque, spinning direction, temperature distribution along the stator windings and on the rotor surface as well as the stator wave frequency. This all-optical sensing solution reduces the component count of conventional sensor systems, i.e., all 48 sensing elements are contained within the machine operated by a single sensing interrogation unit. In this work, the sensing system has been successfully integrated into and tested on a permanent magnet motor prototype.
Improved reference system for high precision blade tip timing on axial compressors
Author(s):
R. Reinhardt;
D. Lancelle;
O. Hagendorf;
M. Schultalbers;
O. Magnor;
P. Duenow
Show Abstract
Blade tip timing is an upcoming technology to research possibilities of working point identification and phenomena like stall and blade vibrations for axial compressors. This method determines blade bendings for each individual compressor blade. Due to their high timing resolution optical sensors are often used in this field. Real blade bendings are often of very small amplitudes in the range of micrometers. So it's important to have a reference system that is as accurate as possible. This paper describes a method which guarantees a high resolution and high precision reference system to improve the results of blade tip timing.
Towards detection of pipeline integrity threats using a smart fiber optic surveillance system: PIT-STOP project blind field test results
Author(s):
J. Tejedor;
J. Macias-Guarasa;
H. F. Martins;
D. Piote;
J. Pastor-Graells;
S. Martin-Lopez;
P. Corredera;
G. De Pauw;
F. De Smet;
W. Postvoll;
C. H. Ahlen;
M. Gonzalez-Herraez
Show Abstract
This paper presents the first report on on-line and final blind field test results of a pipeline integrity threat surveillance system. The system integrates a machine+activity identification mode, and a threat detection mode. Two different pipeline sections were selected for the blind tests: One close to the sensor position, and the other 35 km away from it. Results of the machine+activity identification mode showed that about 46% of the times the machine, the activity or both were correctly identified. For the threat detection mode, 8 out of 10 threats were correctly detected, with 1 false alarm.
Fluorescence ratiometric optical broad range pH sensor based on CdSe/ZnS quantum dots and O170 embedded in ethyl cellulose matrix
Author(s):
Cheng-Shane Chu;
Chih-Jen Su
Show Abstract
This paper presents a ratiometric optical broad range pH sensor that comprises an optical fiber coated at one end with CdSe/ZnS quantum dots (QDs) and Oxazine 170 perchlorate (O170) embedded in ethyl cellulose (EC) matrix. The feasibility of coating an optical fiber with the sensing film to fabricate a ratiometric fiber optic broad range pH sensor is investigated. Using an LED with a central wavelength 405 nm as an excitation light source, the CdSe/ZnS QDs shows that the emission wavelength at 575 nm highly sensitive to pH and O170 shows the emission wavelength at 655 nm insensitive to pH. The ratio of fluorescence intensities at 575 nm and 655 nm has a linear relationship with pH in the 0.9–12.2 range. The ratiometric sensing approach presented in this study has the advantage of suppressing spurious fluctuations in the intensity of the excitation source and optical transmission properties of the optical fiber sensor.
Optical carbon dioxide sensor based on the colorimetric change of α-naphtholphthalein and internal reference fluorescent CIS/ZnS QDs
Author(s):
Cheng-Shane Chu;
Meng-Wei Hsieh
Show Abstract
A new optical carbon dioxide sensor based on the colormetric change of pH indicator α-naphtholphthalein with the internal reference fluorescent CIS/ZnS quantum dots (QDs) was developed. The luminescence intensity of CIS/ZnS QDs increased with increasing carbon dioxide concentration. The sensing films consisting of α-naphtholphthalein in polyIBM and CIS/ZnS QDs in polystyrene layer. The sensitivity of optical carbon dioxide sensor is quantified in terms of the ration I100/I0, where I100 and I0 represent the detected luminescence intensities in pure carbon dioxide and pure nitrogen environments, respectively. The experimental result reveals that the new optical carbon dioxide sensor has sensitivity of I100/I0=13.4.
A new measurement scheme for delay parameters in TDM fiber optic interferometric sensor network
Author(s):
Fei Liu;
Xiaokang Qiu;
Bin Xie;
Lijuan Gu;
Xiaoping Zheng;
Min Zhang
Show Abstract
In this paper, a new scheme for delay parameters measurement in time division multiplexing (TDM) fiber optic interferometric sensor (FOIS) network is proposed. This scheme provides a solution of delay parameters measurement through the variance vector of the reshaped original data. By calculating the correlation between the variance vector and the system's pulse template vector, the scheme is capable to resist much more noise in the original data. Even when the SNR of the original data decreases to 7 dB, the scheme can still work with a correct rate higher than 98%. What's more, the scheme is feasible to be carried out, and it is able to work real-time.
Towards on-line radiation monitoring with perfluorinated polymer optical fibers
Author(s):
P. Stajanca;
K. Krebber
Show Abstract
Sensitivity of two commercial perfluorinated (PF) polymer optical fibers (POFs) to gamma radiation was measured, compared and exploited for dosimetry purposes. Fiber radiation induced attenuation (RIA) was found to be highly wavelength dependent and pronounced towards the UV part of the spectrum. PF-POFs were shown to be highly radiation sensitive and RIA-based on-line radiation monitoring with sensitivity as high as 135 dBm-1/kGy was demonstrated at 460 nm with co-extruded PF-POF. In addition, thanks to low inherent attenuation in the near-infrared region, possibility of distributed radiation detection with PF-POFs was demonstrated for the first time, utilizing optical time domain reflectometry.
Development of ratiometric optical fiber sensor for ammonia gas detection
Author(s):
Cheng-Shane Chu;
Yen-Fu Chen
Show Abstract
A simple, low cost technique to fabricate a ratiometric optical fiber ammonia (NH3) sensor has been presented. The ratiometric optical fiber ammonia sensor was based on the ammonia induced absorbance change of sensing material Oxazine 170 perchlorate (O170) in ethyl cellulose (EC) with the luminescence intensity of 7-amino-4-trifluoromethyl coumarin (AFC). The observed luminescence intensity from AFC at 487 nm decreased with increasing the ammonia concentration. The sensitivity of optical ammonia sensor is quantified in terms of the ratio I0/I100, where I0 and I100 represent the detected luminescence intensities in nitrogen and 1000 ppm ammonia concentration, respectively. The experimental result shows that the sensitivity of the ratiometric optical fiber ammonia sensor is estimated to be 1.44. The sensitive optical ammonia sensor based on fluorescence intensity changes of AFC due to the absorption change of Oxazine 170 perchlorate in EC layer with ammonia is achieved. The ratiometric sensing approach presented in this study has the advantage of suppressing spurious fluctuations in the intensity of the excitation source and optical transmission properties of the optical sensor.
Femtosecond laser inscription of phase-shifted grating by post-processing
Author(s):
Xian Zhou;
Yutang Dai;
Fufei Liu;
Joseph Muna Karanja;
Meng Zou
Show Abstract
The method of fabricating phase-shifted fiber Bragg grating (PSFBG) that does not need a phase mask by femtosecond laser (fs) post-processing is demonstrated. A central region of standard single mode fiber Bragg grating (FBG) is irradiated by fs laser. A rotating jig is designed to hold and rotate the fiber when the fiber is irradiated by laser. The bandwidth of transmission peak of PSFBG and the transmission loss is growing with increasing of laser energy. PSFBG produced by this method is simple, fast and reproducible.
Regeneration characteristics of FBG writen for the visible spectral range
Author(s):
Camila Carvalho de Moura;
Patrícia Loren Inacio;
Ismael Chiamenti;
Valmir de Oliveira;
Hypolito José Kalinowski
Show Abstract
We report regeneration studies of fiber Bragg gratings with resonance band in the visible spectral range. The FBG were produced by direct illumination under the phase mask using UV light from a fs-laser pumped optical parametric amplifier. Some seed gratings were not so saturated as common C-Band gratings written by other methods but their regeneration efficiency is quite high. The final line-widths are narrower than the similar C-band regenerated gratings.
Optical fibre Fabry-Pérot sensor stability at high temperatures
Author(s):
Dimitrios Polyzos;
Jinesh Mathew;
William N. MacPherson;
Duncan P. Hand;
Robert R. J. Maier
Show Abstract
In this paper we present long-term stability results for a Fabry-Pérot optical fibre sensor in high temperatures environments. We introduce an intrinsic Fabry-Pérot type of sensor, which its sensing element is made with an undoped pure fused silica cavity. Furthermore, we will present results detailing dopant diffusion from core to cladding of standard optical fibres demonstrating their inherent unsuitability for high temperature environments. Finally, we display the manufacturing technique required to produce this sensor and we present results of 33 days long stability tests conducted at elevated temperatures of more than 900°C.
Multilevel temperature threshold sensor based on photonic crystal fiber transducers
Author(s):
P. Marć;
N. Przybysz;
K. Stasiewicz;
L. R. Jaroszewicz
Show Abstract
In the paper we have presented a multilevel temperature threshold sensor. The sensor’s transducers were made by filling a commercially available Photonic Crystal Fiber - LMA-10. As a filling material we used a selected group of n-alkanes with different melting points. We have prepared a set of transducers and they were tested in an intensity based sensor configuration. The experimental results of the four transducers’ sensors showed that it is possible to distinguish five threshold levels from the sensor output signal which were correlated with measured temperatures of ON and OFF states for particular transducers.
Highly sensitive gas refractometer based on inverse mode-coupling of cladding-to-core modes in a tapered four-core fiber
Author(s):
Zhihua Shao;
Xueguang Qiao;
Qiangzhou Rong
Show Abstract
A highly sensitive gas refractometer based on inverse mode-coupling is proposed and experimentally demonstrated. The sensor has a sandwiched configuration that a tapered four-core fiber is spliced between two standard single mode fibers. In the tapered four-core fiber, inverse mode-coupling from cladding modes to core modes leads to enhanced cladding modes and evanescent fields. The unique waveguide structure (multiple cores arranged close to the fiber cladding) of the four-core fiber enables multiple core modes to sense refractive index change after tapering. The abrupt taper also acts as a bridge between surround refractive index and interference modes (including both cladding and core modes). For the carbon dioxide refractive index (close to 1.0) measurement, the sensor presents a high sensitivity of 922.32 dB/refractive index unit without cross-sensitivity of temperature.
Gas pressure sensing based on antiresonant reflecting guidance hollow-core fiber
Author(s):
Maoxiang Hou;
Yiping Wang;
Feng Zhu;
Ying Wang;
Changrui Liao
Show Abstract
Gas pressure sensor based on an antiresonant reflecting guidance mechanism in a hollow-core fiber (HCF) with an open microchannel is experimentally demonstrated. The microchannel is created on the ring cladding of the HCF by femtosecond laser to provide an aircore pressure equivalent to the external pressure. The HCF cladding functions as an antiresonant reflecting waveguide, which induces sharp periodic losses in its transmission spectrum. The proposed sensor is miniature, robust, and exhibits a high pressure sensitivity of 3.592 nm/MPa, a low temperature cross-sensitivity of 7.5 kPa/°C.
A novel and small curvature sensor based on butterfly-shape Mach-Zehnder interferometer
Author(s):
Mao-qing Chen;
Yong Zhao;
Ri-qing Lv;
Feng Xia
Show Abstract
A novel hollow-core fiber (HCF) curvature sensor based on a tapered HCF sandwiched between two single mode fibers (Butterfly-Shape Structure) is proposed and experimentally demonstrated. The collapsed region around the first fusion interface excites the high-order modes, and the butterfly shape couples the high-order modes back into the core and interferes with the fundamental mode in the second fusion interface. Simulation of the butterfly-shape structure is carried out using the beam propagation method to determine an optimized size of sensing element. The experimental results show that the variation of the interference spectrum light intensity is almost linearly proportional to the change of curvature, and the curvature sensitivity and resolution of the proposed sensor can be up to −10.9041dB / m−1 and 0.000917m−1 respectively in the range from 0.387 to 1.285 m−1. The proposed curvature sensor is compact size, high sensitive, and inexpensive.
Palladium based hydrogen sensors using fiber Bragg gratings
Author(s):
Maximilian Fisser;
Rodney A. Badcock;
Paul D. Teal;
Arvid Hunze
Show Abstract
This paper reports on the development, and evaluation, of fiber optic hydrogen sensors based on fiber Bragg gratings (FBG) and an experimental measurement system for long term experiments of fiber optic gas sensors. Two types of palladium metal sensors were manufactured; sputter coated and modified palladium foil with 20 and 100 μm thickness. The responses (at 90 °C with both 1 and 5 % hydrogen) of the coated sensor, the 20 μm and 100 μm foil sensor was found to be 10, 160 and 80 pm respectively to 1 % hydrogen and 25, 480 and 225 pm respectively to 5% hydrogen.
Functionalization of a long period grating coated with gold nanoparticles for glyphosate detection
Author(s):
Bárbara R. Heidemann;
Júlia C. Pereira;
Ismael Chiamenti;
Marcela M. Oliveira;
Marcia Muller;
José L. Fabris
Show Abstract
This work describes a method for producing a nanostructured fiber optic device for sensing of pesticides in water environment. The device consists of a long period grating with a coating of gold nanoparticles functionalized with cysteamine. The LPG shows attenuation bands near the phase matching turning point at the visible spectral range. A bottom-up production route was used to deposit gold nanoparticles on the fiber surface. Sensitivity to the refractive index of the external medium was measured before and after the layer deposition. Cysteamine was used as a ligand for glyphosate present in water at a concentration of 100 μM.
QEPAS nitric oxide sensor based on a mid-infrared fiber-coupled quantum cascade laser
Author(s):
Wei Ren;
Chao Shi;
Zhen Wang;
Chenyu Yao
Show Abstract
We report a quartz-enhanced photoacoustic sensor (QEPAS) for nitric oxide (NO) detection using a mid-infrared fibercoupled quantum cascade laser (QCL) near 5.2 μm. The QCL radiation was coupled into an InF3 fiber (100 μm core diameter) for light delivery to the quartz tuning fork, a tiny piezoelectric element converting the acoustic wave induced mechanical vibration to the gas-absorption associated electrical signal. This mid-infrared fiber can achieve nearly single-mode light delivery for the target wavelength. The off-beam configuration was adopted for the fiber-coupled detection considering its simpler installation, optical alignment and comparative sensitivity to the traditional on-beam setup.
High-speed demodulation system of identical weak FBGs based on FDML wavelength swept laser
Author(s):
Yiming Wang;
Quan Liu;
Honghai Wang;
Chenchen Hu;
Chun Zhang;
Zhengying Li
Show Abstract
An identical weak reflection FBGs demodulation system based on a FDML laser is proposed. The laser is developed to output a continuous wavelength-swept spectrum in the scanning frequency of 120 kHz over a spectral range of more than 10nm at 1.54 μm. Based on this high-speed wavelength-swept light and the optical transmission delay effect, the demodulation system obtains the location and wavelength information of all identical weak FBGs by the reflected spectrum within each scanning cycle. By accessing to a high-speed FPGA processing module, continuous demodulation of 120 kHz is realized. The system breakthroughs the bandwidth of the laser to expand the sensors capacity and greatly improves the demodulation speed of a TDM sensing network. The experiments show the system can distinguish and demodulate the identical weak FBGs and measure the 4 kHz vibration at 120 kHz demodulation speed.
Graphene oxide modified surface plasmon resonance sensor based on side-polished fiber
Author(s):
Jing Zhao;
Ying Wang;
Changrui Liao;
Shaoqing Cao;
Mingquan Li;
Yiping Wang
Show Abstract
A Graphene Oxide (GO) modified surface plasmon resonance (SPR) sensor based on the silver-coated side-polished fiber was demonstrated. Stable GO aqueous dispersion was prepared through sonication, confirmed by UV-vis absorption spectrum and Tyndall effect. GO nanosheets were decorated on the Octadecanethiol (ODT)-silver sensor surface, where ODT act as a link between the silver and GO nano-films. The GO decoration process was in-situ monitored by SPR wavelength interrogation method. The proposed SPR fiber sensor show a refractive index sensitivity up to 2252.0 nm/RIU in the range of 1.30 ∼ 1.40 RIU and can be used as promising candidate in biosensing.
Fabrication and characterization of an egg-shaped hollow fiber microbubble
Author(s):
Guanjun Wang;
Yinlan Ruan;
Pinggang Jia;
Zhiguo Gui;
Pengcheng Zhang;
Chao Wang;
Shen Liu;
Changrui Liao;
Guolu Yin;
Yiping Wang
Show Abstract
In this paper, an egg-shaped microbubble is proposed and analyzed firstly, which is fabricated by the pressure-assisted arc discharge technique. By tailoring the arc parameters and the position of glass tube during the fabrication process, the thinnest wall of the fabricated microbubble could reach to the level of 873nm. Then, the fiber Fabry–Perot interference technique is used to analyze the deformation of microbubble that under different filling pressures. It is found that the endface of micro-bubble occurs compression when the inner pressure increasing from 4Kpa to 1400KPa. And the pressure sensitivity of such egg-shaped microbubble sample is14.3pm/Kpa. Results of this study could be good reference for developing new pressure sensors, etc.
First step towards an interferometric and localized surface plasmon fiber optic sensor
Author(s):
Harald Ian D. I. Muri;
Andon Bano;
Dag Roar Hjelme
Show Abstract
We present a first demonstration of a novel multi-parameter fiber optic (FO) sensor concept based on gold nanoparticles (GNP) embedded in a stimuli-responsive hydrogel material. A hemispherical hydrogel immobilized on the optical fiber end-face forms a low-finesse Fabry-Perot (FP) interferometer. The GNPs exhibit local surface plasmon resonance (LSPR) that is sensitive towards the refractive index of the surrounding environment, while the stimuli-responsive hydrogel is sensitive towards specific chemical compounds. We evaluate the quality of the interferometric and LSPR signal as a function GNP concentration and of hydrogel swelling degree stimulated by ethanol solutions. The GNPs shows to have little influence on the visibility of the FP etalon, while LSPR of GNP shows to be sensitive towards the surface refractive index rather than bulk refractive index. This demonstration shows that the sensor concept has the potential to be used in applications such as an intravenous two-parametric real-time sensor for medical purpose.
Strain measurement of spiral bevel gear using optical fiber gratings
Author(s):
Nianyun Liu;
Yiming Wang;
Zude Zhou;
Ping Lou
Show Abstract
This paper presents a spiral bevel gear strain measurement using optical fiber gratings. High-speed and heavy-duty spiral bevel gear (SBG) is the key component of the power transmission of intersection axes. Its dynamic mechanical properties greatly influence the working performance of the machine. By building a strain detecting system based on FBG demodulation, we carried out real-time measurements of the distributed strain in the SBG with different torques and different rotation speed. The experimental results show a complete strain waveform from gear-in to gear-out, verifying the feasibility of measuring the strain of SBG using optical fiber gratings.
Fiber optic current sensor using an internal trigger sampling technique
Author(s):
Hyoung-Jun Park;
Chan Il Yeo;
Dong Hoon Son;
Keo-Sik Kim;
Hyun Seo Kang;
Sung Chang Kim;
Minho Song
Show Abstract
We present an advanced demodulation technique for a fiber-optics interferometric current transducer. A quadrature sampling method with internal triggers was adopted for structural simplification and cost-effective phase demodulation. The internal triggers for quadrature signal processing were generated at zero crossing points of an ac-coupled reference signal, which was distinguished from the current-induced interference signal by utilizing fiber Bragg grating. Phase variation was extracted from the arctangent demodulation process. The proposed technique demonstrated accurate and stable phase demodulations performance and better than that of the conventional lock-in amp demodulation.
Swelling clad-type plastic optical fiber alkane sensor with multi-layer cladding using electrospray deposition method
Author(s):
Akira Nakamura;
Yutaka Suzuki;
Masayuki Morisawa
Show Abstract
In this study, we develop a plastic optical fiber (POF) sensor with a double-layer structure cladding consisting of a swelling polymer lower layer and a dye-doped swelling polymer upper layer. Both cladding layers swell and decrease their refractive indices when exposed to alkane vapor. Then, the structure of the POF sensor changes from leaky to waveguide mode. Therefore, the intensity of transmitted light changes remarkably, depending on the presence of alkane. The absorption of light due to the dye in the upper cladding layer increases the change in transmitted light intensity. In this study, we fabricated a POF sensor by using the electrospray deposition method and examined its response to alkane vapor. The results indicate an improvement in the sensitivity of the POF alkane sensor due to the effect of the double-clad layer.
Three-dimensional FEM model of FBGs in PANDA fibers with experimentally determined model parameters
Author(s):
Markus Lindner;
Barbara Hopf;
Alexander W. Koch;
Johannes Roths
Show Abstract
A 3D-FEM model has been developed to improve the understanding of multi-parameter sensing with Bragg gratings in attached or embedded polarization maintaining fibers. The material properties of the fiber, especially Young's modulus and Poisson's ratio of the fiber's stress applying parts, are crucial for accurate simulations, but are usually not provided by the manufacturers. A methodology is presented to determine the unknown parameters by using experimental characterizations of the fiber and iterative FEM simulations. The resulting 3D-Model is capable of describing the change in birefringence of the free fiber when exposed to longitudinal strain. In future studies the 3D-FEM model will be employed to study the interaction of PANDA fibers with the surrounding materials in which they are embedded.
Verification of a three-dimensional FEM model for FBGs in PANDA fibers by transversal load experiments
Author(s):
Bennet Fischer;
Barbara Hopf;
Markus Lindner;
Alexander W. Koch;
Johannes Roths
Show Abstract
A 3D FEM model of an FBG in a PANDA fiber with an extended fiber length of 25.4 mm is presented. Simulating long fiber lengths with limited computer power is achieved by using an iterative solver and by optimizing the FEM mesh. For verification purposes, the model is adapted to a configuration with transversal loads on the fiber. The 3D FEM model results correspond with experimental data and with the results of an additional 2D FEM plain strain model. In further studies, this 3D model shall be applied to more sophisticated situations, for example to study the temperature dependence of surface-glued or embedded FBGs in PANDA fibers that are used for strain-temperature decoupling.
Optimised process for fabricating tapered long period gratings
Author(s):
K. Mullaney;
S. E. Staines;
S. W. James;
R. P. Tatam
Show Abstract
The process of fabricating tapered long period gratings (TLPGs) using a CO2 laser is described. TLPGs with a period spacing of 378 μm, were fabricated by optimization of the taper waist diameter and careful control of the duty-cycle and its uniformity along the length of the grating. The 6-period TLPGs exhibited a pass-band insertion loss of 0.6 dB, resonance band extinction values of 3 dB and had a physical length of 2.27 mm.
Monitoring the fabrication of tapered optical fibres
Author(s):
K. Mullaney;
R. Correia;
S. E. Staines;
S. W. James;
R. P. Tatam
Show Abstract
A variety of optical methods to enhance the process of making optical fibre tapers are explored. A thermal camera was used to both refine the alignment of the optical components and optimize the laser power profile during the tapering process. The fibre transmission was measured to verify that the tapers had the requisite optical characteristics while the strain experienced by the fibre while tapering was assessed using an optical fibre Bragg grating. Using these techniques, adiabatic tapers were fabricated with a 2% insertion loss.
Influence of saturable absorbers on fiber ring laser sensors
Author(s):
L. Rodriguez-Cobo;
M. A. Quintela;
R. Ruiz-Lombera;
R. A. Perez-Herrera;
M. Lopez-Amo;
J. M. Lopez-Higuera
Show Abstract
In this work, a fiber ring laser sensor has been employed to analyze the influence of passive Er-doped fiber acting as saturable absorber. Lasing modes of fiber ring lasers can be reduced by properly locating a saturable absorber that narrows the spectral width of the FBG that selects the lasing wavelength. Employing commercial Er-doped fiber, different configurations have been evaluated, reaching the SLM regime on a ring cavity of several meters. Thus, the achieved strain response of the whole sensor behaves at its mirror FBG, exhibiting linear response to strain.
High-speed vibration measurement by fiber Bragg gratings with Fourier domain mode locking laser
Author(s):
Tatsuya Yamaguchi;
Yukitaka Shinoda
Show Abstract
We developed a high-speed wavelength-swept laser prototype using Fourier domain mode locking (FDML) and a reflection wavelength measuring system that could rapidly measure a fiber Bragg grating (FBG). The prototype FDML laser incorporated a temperature-controlled optical tunable filter and had a sweep bandwidth of 40 nm in the 1.55 μm wavelength band. This system was able to perform high-speed wavelength sweeping with a sweep frequency of 50.7 kHz and had a temporal resolution of 9.9 μs, which was equivalent to half of the laser’s sweep cycle, due to the FDML laser’s bidirectional swept-wavelength. In this paper, we report on high-speed vibration measurements of several kHz by this system using FBGs.
Fiber optic nickel ion sensor based on direct ligand immobilization
Author(s):
R. Raghunandhan;
L. H. Chen;
C. C. Chan
Show Abstract
An inline intermodal no core fiber (NCF) sensor based on direct ligand immobilization for detection of nickel ions (Ni2+) is proposed. Covalently immobilized nickel specific ligand, Meso-Tetra(4-carboxyphenyl)porphine, on the NCF surface serves as adsorption site for Ni2+ and can induce ambient refractive index (RI) change around the NCF on occurrence of binding events. The change in RI results in spectrum wavelength shifts, which was measured for continuous monitoring of Ni2+ concentration. The proposed sensor was observed to exhibit a sensitivity of 121.03 nm/mM towards Ni2+ ions.
Refractive index sensing using a multimode interference-based fiber sensor in a cavity ring-down system
Author(s):
Susana Silva;
Orlando Frazão
Show Abstract
This work presents a multimode interference-based fiber sensor in a cavity ring-down system for sensing temperature-induced refractive index (RI) changes of water. The sensing head is based in multimodal interference (MMI) and it was placed inside the fiber loop cavity of the CRD system. A modulated laser source was used to send pulses down into the fiber loop cavity and an erbium-doped fiber amplifier (EDFA) was placed in the fiber ring to provide an observable signal with a reasonable decay time. The behavior of the sensing head to temperature was studied due to its intrinsic sensitivity to said parameter — a sensitivity of -1.6×10-9 μs/°C was attained. This allowed eliminating the temperature component from RI measurement of water and a linear sensitivity of 580 μs/RIU in the RI range of 1.324–1.331 was obtained.
Optical fiber tactile sensor based on fiber specklegram analysis
Author(s):
Eric Fujiwara;
Francine D. Paula;
Yu Tzu Wu;
Murilo F. M. Santos;
Egont A. Schenkel;
Carlos K. Suzuki
Show Abstract
An optical fiber tactile sensor based on specklegram analysis is demonstrated. The system consists of microbending transducers attached to semi-rigid plates and distributed in form of array. The specklegrams produced by the multimode fibers are recorded and them the variations on fiber status, related to force magnitude, are assessed by specklegrams correlation. Finally, the spatial information was obtained by using a data fusion approach based on Bayesian inference. The sensor presented ∼0.08 N sensitivity and ∼1 mm resolution. Moreover, the data fusion technique provided the estimation of force distribution over a 30 × 30 mm2 area using only 3 fibers.
Fibre Bragg grating sensors for the analysis of pressure distribution at a disc brake/pad interface
Author(s):
B. T. Major;
D. Tiwari;
R. Correia;
S. W. James;
M. Tirovic;
R. P. Tatam
Show Abstract
The use of optical fibre Bragg gratings (FBGs) to monitor the Interface Pressure Distribution (IPD) on an automotive disc brake pad under a variety of loading conditions is studied. The results demonstrate successful strain transfer from the brake pads to the attached FBG sensors under static loading, with a linear response to increasing pressure, and with the measured IPD showing good agreement with that recorded using pressure sensitive paper. Results are also presented demonstrating that changes in the IPD as a result of torque acting on the brake pads can be monitored by the FBG sensors.
High sensitive and selective Escherichia coli detection using immobilized optical fiber microprobe
Author(s):
Yanpeng Li;
Qizhen Sun;
Yiyang Luo;
Yue Li;
Andong Gong;
Haibin Zhang;
Deming Liu
Show Abstract
We proposed and demonstrated a stable, label-free bacteriophage-based sensor of Escherichia coli using microfiber probe. T4 Bacteriophage was covalently immobilized on microfiber surface and E.coli concentration was investigated using the high accurate spectral interference mechanism. By immersing microfiber sensor into different concentration E.coli solution, the relationship between resonant wavelength shift and E.coli concentration was analyzed in the range of 103-107cfu/ml. The proposed method is capable of reliable detection of E.coli concentration as low as 103cfu/ml with a fast response time about 10minutes, which makes the real-time detection of E.coli move on a giant step. Additionally, the sensor has great potential to be applied in the fields like environment monitoring and food safety.
Fiber sensor identification based on incoherent Rayleigh backscatter measurements in the frequency domain
Author(s):
Max Koeppel;
Rainer Engelbrecht;
Stefan Werzinger;
Bernhard Schmauss
Show Abstract
In this work, a fiber identification method based on incoherent optical frequency domain reflectometry (IOFDR) measurements is introduced. The proposed method uses the characteristic interference pattern of IOFDR Rayleigh backscatter measurements with a broadband light source to unambiguously recognize different initially scanned fiber segments. The recognition is achieved by cross-correlating the spatially resolved Rayleigh backscatter profile of the fiber segment under test with a initially measured and stored backscatter profile. This profile was found to be relatively insensitive to temperature changes. It is shown that identification is possible even if the fiber segment in question is installed subsequent to 300m of lead fiber.
Localized surface plasmon resonance refractometer based on no-core fiber
Author(s):
Yan Ru Wang;
Zhi Qiang Tou;
Chun Liu Zhao;
Ping Lam So;
Chi Chiu Chan
Show Abstract
A novel optical fiber refractometer based on localized surface plasmon resonance (LSPR) is presented. The sensor was prepared by splicing a short segment of no-core fiber (NCF) between two multimode fibers. A gold nanoparticles (AuNPs) film was self- assembled on the sidewall of the NCF. When LSPR peak wavelength is used to investigate the refractive index (RI), sensitivity of 121.88 nm/RIU (R2 = 0.9107), 523.14 nm/RIU (R2 = 0.983) with limit of detection 1.64× 10-3 RIU, 3.82× 10−4 RIU over the RI range of 1.33-1.37 and 1.37-1.42, respectively. When normalized transmittance is used to investigate the performance of the sensor, sensitivity of -279 %/RIU (R2 = 0.9922) with limit of detection 4.61 × 10-5 RIU over the RI range of 1.33 -1.42.
Femtosecond laser processing of optical fibres for novel sensor development
Author(s):
Kyriacos Kalli;
Antreas Theodosiou;
Andreas Ioannou;
Amedee Lacraz
Show Abstract
We present results of recent research where we have utilized a femtosecond laser to micro-structure silica and polymer optical fibres in order to realize versatile optical components such as diffractive optical elements on the fibre end face, the inscription of integrated waveguide circuits in the fibre cladding and novel optical fibre sensors designs based on Bragg gratings in the core. A major hurdle in tailoring or modifying the properties of optical fibres is the development of an inscription method that can prove to be a flexible and reliable process that is generally applicable to all optical fibre types; this requires careful matching of the laser parameters and optics in order to examine the spatial limits of direct laser writing, whether the application is structuring at the surface of the optical fibre or inscription in the core and cladding of the fibre. We demonstrate a variety of optical components such as two-dimensional grating structures, Bessel, Airy and vortex beam generators; moreover, optical bridging waveguides inscribed in the cladding of single-mode fibre as a means to selectively couple light from single-core to multi-core optical fibres, and demonstrate a grating based sensor; finally, we have developed a novel femtosecond laser inscription method for the precise inscription of tailored Bragg grating sensors in silica and polymer optical fibres. We also show that this novel fibre Bragg grating inscription technique can be used to modify and add versatility to an existing, encapsulated optical fibre pressure sensor.
Health monitoring of carbon cantilever using femtosecond laser inscribed FBG array in gradient-index CYTOP polymer fibre
Author(s):
Antreas Theodosiou;
Kyriacos Kalli;
Michael Komodromos
Show Abstract
We report on the femtosecond laser inscription of a fibre Bragg grating array in multimode, gradient-index, CYTOP polymer optical fibre and its demonstration as a quasi-distributed sensor for cantilever health monitoring measurements. We exploit the key advantage of polymer optical fibres, having a significantly lower Young’s modulus compared with silica fibres, for vibration measurements. We also modify the typical multi-mode Bragg grating spectrum through control of the femtosecond laser inscription process, thereby producing gratings having single peak wavelength spectra. The sensor array is used to recover the time-dependent, wavelength response from each Bragg grating sensor and extract the mode shape of the beam. The mode shapes of the beam were used to observe “damage” introduced to the cantilever by adding masses to its surface; adjusting the level of damage by using different weights and placing them at different point across the beam. We show that health monitoring measurements are feasible with polymer based fibre Bragg gratings. The accurate and rapid detection of damage points on structural beams and the damage level is an important parameter for improved maintenance and servicing of beams under load and for the prevention of long-term damage.
Hysteresis compensation technique for POF curvature sensors
Author(s):
Arnaldo G. Leal Jr.;
Anselmo Frizera;
Maria José Pontes
Show Abstract
Polymer optical fibers (POF) have higher strain limits, fracture toughness and flexibility in bend if compared to glass optical fibers. These characteristics enable the application of POFs as curvature sensors. However, the polymer is a viscoelastic material, which does not have a constant response with stress or strain. For this reason, a curvature sensor based on POF may present high hysteresis. This paper proposes a dynamic compensation technique based on the angular velocity of the sensor. Results show a hysteresis up to 10 times lower. Furthermore, it results on a simple calibration equation, which can be applied in real-time measurements.
Photonic sensing in highly concentrated biotechnical processes by photon density wave spectroscopy
Author(s):
Roland Hass;
Michael Sandmann;
Oliver Reich
Show Abstract
Photon Density Wave (PDW) spectroscopy is introduced as a new approach for photonic sensing in highly concentrated biotechnical processes. It independently quantifies the absorption and reduced scattering coefficient calibration-free and as a function of time, thus describing the optical properties in the vis/NIR range of the biomaterial during their processing. As examples of industrial relevance, enzymatic milk coagulation, beer mashing, and algae cultivation in photo bioreactors are discussed.
Detection of volatile organic compounds using an optical fiber sensor coated with a sol-gel silica layer containing immobilized Nile red
Author(s):
Dejun Liu;
Xiaokang Lian;
Arun Kumar Mallik;
Wei Han;
Fangfang Wei;
Jinhui Yuan;
Chongxiu Yu;
Gerald Farrell;
Yuliya Semenova;
Qiang Wu
Show Abstract
A simple volatile organic compound (VOC) sensor based on a tapered small core singlemode fiber (SCSMF) structure is reported. The tapered SCSMF fiber structure with a waist diameter of 7.0 μm is fabricated using a customized microheater brushing technique. Silica based material containing immobilized Nile red was prepared by a sol-gel method and was used as a coating applied to the surface of the tapered fiber structure. Different coating thicknesses created by a 2-pass and 4-pass coating process are investigated. The experiments demonstrate that both sensors show a linear response at different gas concentrations to all three tested VOCs (methanol, ethanol and acetone). The sensor with a thicker coating shows better sensitivities but longer response and recovery times. The best measurement resolutions for the 4-pass coating sensor are estimated to be 2.3 ppm, 1.5 ppm and 3.1 ppm for methanol, ethanol and acetone, respectively. The fastest response and recovery time of 1 min and 5 min are demonstrated by the sensor in the case of methanol.
A miniaturized ferrule-top optical cantilever for vibration measurement
Author(s):
J. Li;
S. M. Xu;
J. N. Sun;
Y. Q. Tang;
F. Z. Dong
Show Abstract
In this paper, we propose techniques to design and fabricate polymer micro-cantilevers for attachment onto the end of standard single mode fibers using laser machining. The polymer cantilever is fabricated by laser micro-machining a sheet of polymer into the required shape and then bonded onto the top of a ceramic ferrule by photo resist as a flat supporting and bonding layer. The dimension of resulting cantilever is ~1.2 mm long, ~300 μm wide, and 25 μm thick. In this work we describe the fabrication of single sensors, however the process could be scaled to offer a route towards mass production. Cantilever vibration caused by vibration signal are monitored by a DFB laser based phase interrogation system. Proof-of-concept experiments show that the sensor is capable of detecting vibration signal with a frequency range of 0-800Hz. By using thinner polymer sheet and machining longer cantilever, the frequency response range can be extended up to a few kHz.
Relative humidity sensor based on a few-mode microfiber knot resonator by mitigating group index difference
Author(s):
Duy Duong Anh Le;
Seungmin Lee;
Young-Geun Han
Show Abstract
A few-mode microfiber knot resonator (FM-MKR) incorporating a polyvinyl alcohol (PVA) is investigated for measurement of relative humidity (RH). Two modes, such as HE11 and HE12, are excited and interfered in a nonadiabatically tapered structure of the single-mode fiber (SMF). After making a tie with the few-mode microfiber, the FM-MKR is fabricated. In the FM-MKR, two modes, such as HE11 and HE12, must be circulated within the optical knot and cross-coupled independently with a phase delay. By optimizing the diameter of the microfiber, the difference of group effective refractive indices between two modes is dramatically suppressed resulting in the improvement of RH sensitivity of the proposed FM-MKR.
Optical detection of glyphosate in water
Author(s):
R. E. de Góes;
G. R. C. Possetti;
M. Muller;
J. L. Fabris
Show Abstract
This work shows preliminary results of the detection of Glyphosate in water by using optical fiber spectroscopy. A colloid with citrate-caped silver nanoparticles was employed as substrate for the measurements. A cross analysis between optical absorption and inelastic scattering evidenced a controlled aggregation of the sample constituents, leading to the possibility of quantitative detection of the analyte. The estimate limit of detection for Glyphosate in water for the proposed sensing scheme was about 1.7 mg/L.
Optimization of modal sensitivity in nanowire SPR multimode sensor
Author(s):
D. F. Santos;
A. Guerreiro;
J. M. Baptista
Show Abstract
This paper presents a multimode fiber sensor that uses surface plasmon resonance on a metallic wire to measure refractive index. Numerical simulations based on the finite element method reveal the sensor supports several plasmon modes in the wire capable of coupling with the multiples optical fiber modes. Therefore, the sensor configuration creates multiple resonances at different wavelengths, with different values of the loss, sensitivity, among other parameters. Choosing the appropriate mode and filtering out the rest of the modes allows to optimize the sensor performance. In the present work a sensitivity of 5340nm/RIU and resolution of 1.87×10-6RIU were found.
Fiber Bragg grating sensor based on cantilever structure embedded in polymer 3D printed material
Author(s):
Rita Lima;
R. Tavares;
S. O. Silva;
P. Abreu;
Maria T. Restivo;
O. Frazão
Show Abstract
A cantilever structure in 3D printed based on a fiber Bragg grating (FBG) sensor embedded in polymer material is proposed. The FBG sensor was embedded in 3D printed coating and was tested under three physical parameters: displacement, temperature and vibration. The sensor was tested in displacement in two different regions of the cantilever, namely, on its midpoint and end point. The maximum displacement sensitivity achieved was (3 ± 0.1) pm/mm for end point displacement, and a temperature sensitivity of (30 ± 1) pm/°C was also attained. In the case of vibration measurements it was possible to obtain a 10.23Hz-low frequency oscillation.
Blueberry juices: a rapid multi-analysis of quality indicators by means of dispersive Raman spectroscopy excited at 1064 nm
Author(s):
L. Ciaccheri;
T. Yuan;
S. Zhang;
A. A. Mencaglia;
C. Trono;
L. Yuan;
A. G. Mignani
Show Abstract
Blueberry juices produced in China and in Italy were analyzed by means of Raman spectroscopy. The reference data of important nutraceutical indicators such as degrees Brix and carbohydrates were available. Some juices were produced from fresh organic fruits, while others were industrial grade, differing in qualities and prices. Raman spectra obtained with excitation at 1064 nm were acquired using a dispersive fiber-optic spectrometer. Degrees Brix were measured by means of a commercial refractometer, while carbohydrate contents were available from the producers. Multivariate processing was used for predicting Brix and carbohydrates from Raman spectra and from the reference data. Determination coefficients equal to 0.88 and 0.84, respectively, were obtained. This experiment further confirms the excellent potentials of Raman spectroscopy for both non-destructive and rapid assessments of food quality.
Sapphire Fabry-Perot high-temperature sensor study
Author(s):
Yi-qiang Yao;
Wei-long Liang;
Xinwang Gui;
Dian Fan
Show Abstract
A new structure sapphire fiber Fabry-Perot (F-P) high-temperature sensor based on sapphire wafer was proposed and fabricated. The sensor uses the sapphire fiber as a transmission waveguide, the sapphire wafer as an Fabry-Perot (F-P) interferometer and the new structure of “Zirconia ferrule-Zirconia tube” as the sensor fixing structure of the sensor. The reflection spectrum of the interferometer was demodulated by a serial of data processing including FIR bandpass filter, FFT (Fast Fourier Transformation) estimation and LSE (least squares estimation) compensation to obtain more precise OPD. Temperature measurement range is from 20 to 1000°C in experiment. The experimental results show that the sensor has the advantages of small size, low cost, simple fabrication and high repeatability. It can be applied for longterm, stable and high-precision high temperature measurement in harsh environments.
Microfluidic chip based microfiber/nanofiber sensors
Author(s):
Lei Zhang;
Limin Tong
Show Abstract
We demonstrate three microfluidic chip based microfiber/nanofiber sensors for ultra-sensitive absorption, fluorescence, and femtoliter-scale sensing, respectively. The sensors shown here may open up new opportunities for ultra-sensitive biosensing and single molecule analysis.
Miniature FBG-based fluidic flowmeter to measure hot oil and water
Author(s):
Zhengyong Liu;
Lin Htein;
Lun-Kai Cheng;
Quincy Martina;
Rob Jansen;
Hwa-Yaw Tam
Show Abstract
In this paper, we present a miniature fluidic flowmeter based on a packaged FBG and laser-heated fibers. The flow rates of water and hydraulic oil were measured by utilizing the proposed flowmeter. The measured results exhibited good sensitivity of 0.339 nm/(m/s) for water and 0.578 nm/(m/s) for oil flow. Experimental results showed that the sensitivity of the fluidic flow sensor is depending on the heat capacity of the fluids, where the fluid with higher heat capacity has higher sensitivity and lower detection limit at the same measurement condition. The real-time flow rates measured by the proposed sensor and a commercial flowmeter installed in the test rig were also compared, demonstrating good agreement with correlation coefficient of 0.9974.
Interferometric vs. wavelength selective optical fiber sensors for cryogenic temperature measurements
Author(s):
V. DeMiguel-Soto;
D. Leandro;
A. Lopez-Aldaba;
J. J. Beato-López;
J. I. Pérez-Landazábal;
J.-L. Auguste;
R. Jamier;
P. Roy;
M. Lopez-Amo
Show Abstract
n this work, a preliminary study of the behavior of two different interferometric fiber optic sensors and two different wavelength selective fiber optic sensors is performed. A photonic crystal fiber Fabry-Pérot interferometer, a Sagnac interferometer, a commercial fiber Bragg grating (FBG) and a π-phase shifted fiber Bragg grating interrogated in a random distributed feedback fiber laser are analyzed. A comparison of their sensitivities and resolutions is carried out to analyze their performance as sensors for cryogenic temperatures, taking into account their advantages and drawbacks. Keywords: cryogenic temperature, interferometric sensor, optical fiber sensor, random distributed feedback fiber lasers
Thermal sensing based on whispering gallery modes in tapered-fiber-coupled liquid crystal microdroplets
Author(s):
Yan Wang;
Hanyang Li;
Liyuan Zhao;
Yongjun Liu;
Shuangqiang Liu;
Jun Yang
Show Abstract
We report the efficient coupling of optical whispering gallery modes (WGMs) in liquid crystal microdroplets suspended in immiscible aqueous environment. Individual nematic liquid crystal (NLC) microdroplet is confined at the tip of a microcapillary used to generate the microdroplets and coupled through a tapered optical fiber waveguide positioned in the vicinity of the microdroplets. Efficient coupling of WGMs is observed in the NLC microdroplets with a diameter of 50–150 μm. In addition, the wavelengths of the WGMs can be tuned by temperature, making such NLC microdroplets suitable for thermal sensors. A temperature sensitivity of 0.244 nm/°C is achieved in a 75-μm-diameter microdroplet. The estimated thermal resolution of the microdroplet sensor is 8.2 × 10-2 °C.
Directional curvature sensor based on long period gratings in multicore optical fiber
Author(s):
Javier Madrigal;
David Barrera;
Javier Hervás ;
Hailan Chen;
S. Sales
Show Abstract
Multicore optical fiber can be used to implement multidimensional optical fiber sensors including curvature sensors. In this paper, a selective core inscription technique is used in order to inscribe a single long period grating in each of the outer cores of the optical fiber. A set of three different long period gratings is inscribed for implementing the curvature sensor. The ability of the sensor for measuring the magnitude and the direction of curvature is demonstrated. The optical fiber sensor is characterized experimentally for curvature magnitudes from 0 m-1 to 1.77 m-1 and curvature directions from 0° to 360°.The maximum curvature sensitivity of the developed sensor is -4.85 nm/m-1.
All-fiber hydrogen sensor based on stimulated Raman gain spectroscopy with a 1550-nm hollow-core fiber
Author(s):
Fan Yang;
Wei Jin
Show Abstract
We report a highly sensitive all-fiber hydrogen sensor based on continuous-wave stimulated Raman gain spectroscopy with a hollow-core photonic crystal fiber operating around 1550 nm. A pump-probe configuration is used, in which the frequency difference between the pump and the probe lasers is tuned to the S0(0) transition of para-hydrogen with a Raman shift of 354 cm-1. Preliminary experiments demonstrate a detection limit down to 17 ppm with a 250 s averaging time, and further improvement is possible. The all-fiber configuration operating in the telecommunication wavelength band would enable cost-effective and compact sensors for high sensitivity and high-resolution trace analysis.
A comparison of brazed metal and epoxied fibre Bragg grating strain sensors under high strain regimes
Author(s):
I. Mckeeman;
P. Niewczas;
S. Khan
Show Abstract
Three different fibre Bragg grating strain sensors were tested for their suitability for measuring high strain. The sensor types were: a bare epoxied fibre Bragg grating, a standard fibre Bragg grating epoxied into a metal capillary and, finally, a metal coated fibre Bragg grating brazed into a metal capillary. The sensors were calibrated on a steel specimen up to 1400MPa (equivalent to 7.3mε). The results show that the bare epoxied Bragg grating and the metal packaged grating are suitable for measuring strains of this level.
Optical fiber meta-tips: perspectives in sensing applications
Author(s):
Maria Principe;
Marco Consales;
Alberto Micco;
Alessio Crescitelli;
Giuseppe Castaldi;
Emanuela Esposito;
Vera La Ferrara;
Antonello Cutolo;
Vincenzo Galdi;
Andrea Cusano
Show Abstract
In this work we review the concept of optical fiber meta-tips, recently introduced by the authors. Optical fiber meta-tips come from the integration of plasmonic optical metasurfaces and the fiber optics technology. In particular, this integration is a major breakthrough in the recently emerged “Lab-On-Fiber” technology, where nanostructured platforms with special capabilities of light manipulation are integrated onto the tip of an optical fiber. Optical fiber meta-tips can, on one side, boost the real world applicability of optical metasurfaces, and, on the other side, bring about more advanced capabilities of on-fiber control and manipulation of light wavefront and polarization. With a view towards possible practical applications to label-free chemical and biological sensing, we inspect the potentialities of optical fiber meta-tips to work as sensors of local refractive index variations, and aim at studying the effect that the phase gradient impressed by the metasurface has on the surface sensitivity of proposed devices.
Reproducible SERS substrates on optical fiber tips by nanosphere lithography
Author(s):
M. Pisco;
F. Galeotti;
G. Quero;
G. Grisci;
A. Micco;
L. V. Mercaldo;
P. Delli Veneri;
A. Cutolo;
A. Cusano
Show Abstract
This paper reports on the assessment of a simple and economical self-assembly methodology to obtain reproducible substrates onto the optical fiber tip for surface-enhanced Raman spectroscopy (SERS) applications. The method relies on the use of the nanosphere lithography of the optical fiber end facet. A careful analysis has been carried out to investigate the capability of the proposed procedure to realize repeatable pattern on the optical fiber tip. Finally, we demonstrate the effective application of the patterned OFTs as SERS nanoprobes.
High sensitivity temperature sensor based on a polymer filled hollow core optical fibre interferometer
Author(s):
Rahul Kumar;
Wai Pang Ng;
Yong-Qing Fu;
Jinhui Yuan;
Chongxiu Yu;
Gerald Farrell;
Yuliya Semenova;
Qiang Wu
Show Abstract
A high-sensitivity temperature sensor based on a singlemode-multimode-polymer filled hollow core fibre-multimode-singlemode (SMHMS) fibre structure is proposed. This sensor was made from a short section of hollow core fibre filled with a high thermo-optic coefficient (TOC) polymer with a refractive index close to that of the fibre cladding, fusion spliced between two singlemode-multimode (SM) fibre structures. This sensor effectively improves the temperature sensitivity by over 200 times by comparison to a conventional singlemode-multimode-singlemode (SMS) fibre structure. In this report, we experimentally demonstrate that the proposed sensor provides a high temperature sensitivity of 2.16 nm/°C.
Simultaneous and quasi-independent strain and temperature sensor based on microstructured optical fiber
Author(s):
A. Lopez-Aldaba;
J.-L. Auguste;
R. Jamier;
P. Roy;
M. Lopez-Amo
Show Abstract
In this paper, a new sensor system for simultaneous and quasi-independent strain and temperature measurements is presented. The interrogation of the sensing head has been carried out by monitoring the FFT phase variations of two of the microstructured optical fiber (MOF) cavity interference frequencies. This method is independent of the signal amplitude and also avoids the need to track the wavelength evolution in the spectrum, which can be a handicap when there are multiple interference frequency components with different sensitivities. The sensor is operated within a range of temperature of 30°C-75°C, and 380με of maximum strain were applied; being the sensitivities achieved of 127.5pm/°C and -19.1pm/με respectively. Because the system uses an optical interrogator as unique active element, the system presents a cost-effective feature.
Multi-parameter measurements using optical fibre long period gratings for indoor air quality monitoring
Author(s):
J. Hromadka;
S. Korposh;
M. C. Partridge;
S. James;
F. Davis;
D. Crump;
S.-W. Lee;
R. P. Tatam
Show Abstract
An array of three long period gratings (LPGs) fabricated in a single optical fibre and multiplexed in the wavelength domain was used to measure simultaneously temperature, relative humidity (RH) and volatile organic compounds (VOCs). Each LPG sensor was designed to optimize its response to a desired measurand. The LPGs were fabricated with periods such that they operated at or near the phase matching turning point. The sensors were calibrated in the laboratory and the simultaneous measurement of the key indoor air quality parameters was undertaken in laboratory and office environments. It was demonstrated successfully that the data produced by the LPG sensor array under real conditions was in a good agreement with that produced by commercially available sensors. Further, the potential application of fibre optic sensors for VOCs detection at high levels has been demonstrated.
Fabry-Pérot based refractive index optical fiber sensor for measurement of oxygen concentration levels in hypoxic tumors during radiotherapy treatment
Author(s):
Charusluk Viphavakit;
DineshBabu Duraibabu;
Sinead O'Keeffe;
Elfed Lewis
Show Abstract
An optical fiber sensor based on Fabry-Pérot interferometer to measure the refractive index changes due to oxygenation level changes in hypoxic tumors for radiotherapy treatments is proposed. The sensors have an outer diameter of 220μm with a 20-30μm length air-cavity and a 30μm thickness end cap located at the tip of the sensor. The sensors are used to measure the phase change in the received optical spectrum when there is a change in refractive index using a Fast Fourier Transform based analysis method. The refractive index change is measured in order to determine the oxygenation level in hypoxic tumors. In this paper, different concentrations of iso-propanol solution are prepared to produce refractive index values between 1.3438 and 1.3655 in order to mimic the refractive index of hemoglobin. The sensors are coated with a 100 nm thick gold layer and a comparison is made with non-coated sensors. The coated sensors have a resolution in order of 10-3 RIU.
Relative humidity multi-point optical sensors system based on fast Fourier multiplexing technique
Author(s):
A. Lopez-Aldaba;
D. Lopez-Torres;
C. Elosua;
J.-L. Auguste;
R. Jamier;
P. Roy;
F. J. Arregui;
M. Lopez-Amo
Show Abstract
In this paper, a new multipoint optical fiber system for relative humidity measurements based on SnO2-FP (Fabry-Pérot) sensing heads and an optical interrogator as single active device is presented and characterized. The interrogation of the sensing heads is carried out by monitoring the Fast Fourier Transform phase variations of the FP (Fabry-Pérot) interference frequencies. This method allows to multiplex several sensors with different wavelength spacing interference pattern. The sensors operate within a wide humidity range (20%–90% relative humidity) with low crosstalk between them. Five sensing heads have been measured using two different channels of the optical interrogator. The availability of four channels in the interrogator allows to multiplex a higher number of sensors, reducing proportionally the cost of each sensing point.
High temperature sensing with single material silica optical fibers
Author(s):
Stephen C. Warren-Smith;
Linh V. Nguyen;
Heike Ebendorff-Heidepriem;
Tanya M. Monro
Show Abstract
We present recent developments in high temperature sensing using single material silica optical fibers. By using a single material fiber, in this case a suspended-core fiber, we avoid effects due to dopant diffusion at high temperature. This allows the measurement of temperatures up to the dilatometric softening temperature at approximately 1300°C. We demonstrate and compare high temperature sensing in two configurations. The first exploits a small section of single material fiber spliced onto a length of conventional single mode fiber, which operates through multimode interference. The second utilizes a type II fiber Bragg grating written via femtosecond laser ablation.
Refractive index sensor based on theta-shaped microfiber resonator and Vernier effect
Author(s):
Zhilin Xu;
Yiyang Luo;
Qizhen Sun;
Perry Ping Shum;
Zhifang Wu;
Xuguang Shao;
Deming Liu
Show Abstract
A compact refractive index (RI) sensing probe with controllable sensitivities based on a θ-shaped microfiber resonator and Vernier effect is reported. By cascading the θ-shaped microfiber resonator with a fiber Fabry-Perot interferometer, Vernier effect is generated to enhance the RI sensitivity. Both theoretical analyses and experimental results demonstrate that the RI sensitivity can be tuned by changing the cavity length of the θ-shaped microfiber resonator. The RI sensitivity is widely tuned from 311.77nm/RIU to 2460.07nm/RIU in the experiment. The θ-shaped microfiber resonator and the proposed method of generating Vernier effect could find important applications in optical fiber sensing field.
Highly sensitive fiber optic Fabry-Perot geophone with graphene coated PMMA membrane
Author(s):
C. B. Yu;
Y. Wu;
F. Wu;
C. Li;
J. H. Zhou;
Y. J. Rao;
Y. F. Chen
Show Abstract
A highly sensitive fiber-optic Fabry-Perot interferometric geophone (FFPG) with graphene coated PMMA membrane is proposed and demonstrated, where the graphene coating is used for enhancement of the mechanical strength of the membrane. It is found that the sensitivity of the FFPG is much higher than that of the conventional electrical geophone. Such a novel all-optical geophone with low cost, high sensitivity, electromagnetic interference immunity, easy fabrication and robust structure would have great potential for use in oil/gas exploration and seismic wave detection.
LPFG based fiber optic sensor for magnetic field measurement
Author(s):
Carlos A. J. Gouveia;
Luís Coelho;
Marcos A. R. Franco
Show Abstract
The design and modelling of a novel magnetic field sensor based on a long period fiber grating coated with a thin film of N doped ZnO is reported. The parameters of both, the grating and the thin film were carefully chosen to operate in the transition mode and near to the dispersion turning point. At this point, an LPFG shows its maximum sensitivity to external refractive index variations. The magnetic field induces variations in the coating refractive index, which changes the effective refractive index of the cladding mode and the consequent spectral response. In this work a sensitivity to the surrounding magnetic field of 2.9 nm/mT is reported with a maximum theoretical resolution of 2 μT.
The sensing characteristic of ultra-weak FBG inscribed on splice joint
Author(s):
Ye Tian;
Quan Chai;
Qiang Liu;
Yichen Meng;
YanLei Liu;
Jing Ren;
Song Wang;
Jianzhong Zhang;
Wenping Zhang;
Jun Yang;
Zhihai Liu;
Libo Yuan
Show Abstract
FBG inscribed on splice joint is proposed to be used as a sensor. It could realize temperature and strain measurement simultaneously because of the different strain responses of the different parts of the FBG inscribed on splice joint, while the temperature responses are same. The strain responses of four overlap values are discussed, which is used to optimize the discrimination capability of the strain and temperature response of the FBG device.
High spatial resolution multiplexing of fiber Bragg gratings using single-arm frequency-shifted interferometry
Author(s):
Zeng Xiong;
Ciming Zhou;
Huiyong Guo;
Dian Fan;
Yiwen Ou;
Yi Liu;
Chunran Sun;
Li Qian
Show Abstract
We demonstrate a high spatial resolution multiplexing scheme for fiber Bragg grating (FBG) sensors based on single-arm frequency-shifted interferometry (SA-FSI). The SA-FSI system uses an incoherent broadband source, a slow detector, and an electro-optic modulator (EOM). By sweeping the frequency of EOM and taking the fast Fourier transform (FFT) of the interference signal, we resolved the locations of FBGs distributed both in parallel and in series along fiber links despite their reflection spectral overlap. Eighteen weak FBGs (~5% reflectivity) separated by ~0.1 m were clearly resolved experimentally, sweeping EOM modulation frequency in the range of 2-11 GHz.
Optical sensing with antiresonant capillary fibers
Author(s):
Jonas H. Osório;
Thiago H. R. Marques;
Igor C. Figueredo;
Valdir A. Serrão;
Marcos A. R. Franco;
Cristiano M. B. Cordeiro
Show Abstract
Herein, we present a study of the use of polymer capillary optical fibers in sensing measurements. In particular, we approach the application of these fibers for temperature sensing. To do this, an analytical model for describing the spectral characteristics of the light transmitted through the capillaries was employed. Thermal expansion and thermooptic effect influences on the transmitted spectrum were evaluated. Moreover, a 140 ± 6 pm/°C temperature sensitivity was measured, which is in good resemblance to simulated data and is around 14 times higher than the sensitivity attained in conventional Bragg gratings sensors.
Fiber laser accelerometer-magnetometer
Author(s):
Zhaogang Wang;
Wentao Zhang;
Wenzhu Huang;
Fang Li
Show Abstract
A fiber optic accelerometer-magnetometer (FLAM), which can measure acceleration and magnetic field simultaneously, based on fiber laser sensing is proposed. The principle of the FLAM and the theory of the decoupling the signals of acceleration and magnetic field are presented. The FLAM was interrogated using phase-generated-carrier (PGC) method. A test of simultaneously measuring acceleration and magnetic field was performed. The results show that the responding mixed signal achieves a good SNR and prove that the function of the sensor has been realized and the theory of decoupling signal is reliable.
Detection of glycoprotein using fiber optic surface plasmon resonance sensors with boronic acid
Author(s):
Fang Wang;
Yang Zhang;
Zigeng Liu;
Siyu Qian;
Yiying Gu;
Zhenguo Jing;
Changsen Sun;
Wei Peng
Show Abstract
In this paper, we present a tilted fiber Bragg gratings (TFBG) based surface Plasmon resonance (SPR) label-free sensors with boronic acid derivative (ABA-PBA) as receptor molecule to detect glycoprotein with high sensitivity and selectivity. Tilted fiber Bragg gratings (TFBG) as a near infrared wavelengths detecting element can be able to excite a number of cladding modes whose properties can be detected accurately by measuring the variation of transmitted spectra. A 10° TFBG coated by 50nm gold film was manufactured to stimulate surface plasmon resonance on the surface of the sensor. The sensor was loaded with boronic acid derivative as the recognition molecule which has been widely used in various areas for the recognition matrix of diol-containing biomolecules. The proposed TFBG-SPR sensors exhibit good selectivity and repeatability with the protein concentration sensitivity up to 2.867dB/ (mg/ml) and the limit of detection was 2*10-5g/ml.
A novel inter-fibre light coupling sensor probe using plastic optical fibre for ethanol concentration monitoring at initial production rate
Author(s):
Sanober F. Memon;
Elfed Lewis;
J. Tony Pembroke;
Bhawani S. Chowdhry
Show Abstract
A novel, low cost and highly sensitive optical fibre probe sensor for concentration measurement of ethanol solvent (C2H5OH) corresponding to bio-ethanol production rate by an algae is reported. The principle of operation of the sensor is based on inter-fibre light coupling through an evanescent field interaction to couple the light between two multimode fibres mounted parallel to each other at a minimum possible separation i.e. ~ < 1mm. The sensor was fabricated using a low cost 1000um plastic optical fibre (POF) and was characterized for real time measurement in the broadband spectrum including visible and near infra-red. The wavelength dependency of this sensor design was also investigated by post processing analysis of real time data and hence the optimum wavelength range determined. The proposed sensor has shown significant response in the range of 0.005 – 0.1 %v/v (%volume/volume or volume concentration) which depicts the high sensitivity for monitoring very minute changes in concentration corresponding refractive index changes of the solution. Numerically, sensor has shown the sensitivity of 21945 intensity counts/%v/v or 109.7 counts per every 0.0050 %v/v.
Optimization of output signal power spectrum in Raman-assisted WDM system
Author(s):
Shilin Sun;
Liangjin Huang;
Jianfei Wang;
Zhou Meng
Show Abstract
We analyze the output signal power spectrum with different initial input signal power spectrum in a long-haul wavelength-division-multiplexed system with backward multiple-pump Raman amplifiers. The genetic algorithm is used to optimize the output signal power. The results using fixed pump wavelengths are compared with the case in which the pump wavelengths are allowed to vary. We experimentally show that the optimal design algorithm is proper.
Microwave photonics filtering interrogation technique under coherent regime for hot spot detection on cascaded FBG fiber
Author(s):
Javier Hervás;
David Barrera;
Javier Madrigal;
Salvador Sales
Show Abstract
An interrogation technique of cascaded FBGs sensors based on a Microwave Photonics filtering technique under coherent regime is presented. The sensing information of a 5m fiber coil with 500 weak FBGs with a similar central wavelength is retrieved. The principle of operation is based on the calculation of the impulsive response by recording the electrical frequency response of the system. Hot spot detection and temperature measurement are demonstrated through experimental measurements with a temperature sensitivity of 0.6dB/ºC. The resolution in the measurement is related to the bandwidth of the electrical measurement and we have obtained a resolution of 20 cm for an electrical bandwidth of 1 GHz and a SNR bigger than 16dB.
Phase modulation to intensity modulation conversion for sensitive FBG sensor interrogation
Author(s):
Javier Hervás;
David Barrera;
Javier Madrigal;
Salvador Sales
Show Abstract
An interrogation technique based on phase modulation to intensity modulation conversion due to FBG filtering is presented. A 10 GHz tone is used to phase modulate an optical carrier located at the Bragg wavelength of a given FBG. The modulation index is set to a small value to keep Bessel identities close to 0 in order to avoid higher harmonics. Changes of the Bragg wavelength cause a power change in the photodetected 10 GHz tone. A remarkable linear sensitivity of 1 dB/pm for a shift up to 10 pm of the Bragg wavelength is demonstrated through experimental measurements. The range with linear sensitivity can be enlarged sweeping the source wavelength. This proves that the presented interrogation technique is able to interrogate FBGs with a resolution far below 1 pm and no need of extra postprocessing.
Bromothymol blue coated fiber optic Fabry-Perot interferometer for ammonia gas sensor
Author(s):
Dnyandeo Pawar;
S. A. Mane;
S. N. Kale
Show Abstract
A single mode fiber is used in this study, in a Y-coupler mode; the mirror tip of which is coated with bromothymol blue (BTB), homogeneously mixed in polyvinyl alcohol (PVA) matrix. The setup operated at 1550 nm, and was used to sense extremely small quantities of ammonia gas, at room temperature. The sensor is able to detect ammonia in the range of 1.5 ppm to 150 ppm; with observed sensitivity in terms of wavelength shift of 0.7 nm. The sensor showed excellent reversibility with fast response and recovery time of the order of few seconds. The possible interaction of dye with ammonia was studied and compared with chloroform.
Mach-Zehnder interferometer in embedded-core optical fiber
Author(s):
Jianan Fu;
Meng Wang;
Peng Huang;
Jing Yang;
Zheng Zhu;
Chunying Guan;
Libo Yuan
Show Abstract
A novel Mach-Zehnder interferometer (MZI) based on a pair of long period fiber gratings (LPGs) in an embedded-core hollow optical fiber (ECOF) are proposed and demonstrated experimentally. Two similar LPGs with peak attenuation of approximately 3dB are fabricated in an ECOF by using high-frequency CO2 laser to form an in-fiber MZI. The dependences of the resonant peak on the temperature and the axial strain were studied. Experimental results show that sensitivities of the temperature and the axial strain are 64.3 pm/°С and 0.4 pm/με, respectively.
Measuring of the pitch variation of cholesteric liquid crystals under electric field using wavelength-swept laser
Author(s):
Myeong Ock Ko;
Sung-Jo Kim;
Jong-Hyun Kim;
Min Yong Jeon
Show Abstract
We measure the pitch variation of cholesteric liquid crystals (CLCs) according to the applied electric field using a wavelength-swept laser. While the electric field is applied to the CLC, the pitch of the CLC is elongated normal to the direction of electric field. Therefore, the reflection band is shifted to the longer wavelength. When the applied electric field to the CLC cell was over 1.52 V/μm, the reflection band was changed to the longer wavelength of about 75.1 nm. We believe that the dynamic behavior of the CLC can be analyzed if a high-speed wavelength-swept laser is used as an optical source.
Graphene oxide coated long period grating based fibre optic humidity sensor
Author(s):
Kasun P. W. Dissanayake;
Weiping Wu;
Hien Nguyen;
Tong Sun;
Kenneth T. V. Grattan
Show Abstract
In this paper, the response of a graphene oxide (GO) coated long period grating (LPG) to the change in temperature and in humidity is reported. To create the probe, an improved Hummer’s method was used to synthesis the GO solution used as its basis, allowing coating of functionalized LPG by using a multi-layer dip coating technique. A consistent and stable response of the resonance peak intensity of the GO coated LPG was observed to the change in humidity, achieving a sensitivity of 0.15 dB / %RH with a linear correlation coefficient of 0.9804 over the relative humidity range from 60%RH to 95%RH at room temperature (25 °C). A blue shift of the resonance peak wavelength was recorded when the proposed sensor was exposed to varying temperature conditions from 25 °C to 70 °C and the response was found to be linear with a correlation coefficient of 0.9973. The GO coated LPG humidity sensor probe performed with a good stability and repeatability over a number of test cycles in this initial performance evaluation.
Fiber optic sensor for simultaneous strain and temperature monitoring in composite materials at cryogenic condition
Author(s):
Umesh Sampath;
Dae-gil Kim;
Hyunjin Kim;
Minho Song
Show Abstract
Low thermal sensitivity and cross sensitivity of Fiber Bragg Grating (FBG) towards the applied strain, temperature make FBG implementation complicated in composite materials at cryogenic conditions. In order to alleviate this problem, our work focuses on simultaneous strain and temperature monitoring inside the composite material at cryogenic temperatures. The temperature sensitive polymer coating on an FBG sensor makes it a suitable candidate for cryogenic temperature measurement. The average temperature sensitivity of 48 pm °C-1 was obtained in -180 ~ 25 °C. In addition, the cross sensitivity problem has been adjusted by introducing a glass capillary tube to encapsulate the FBG. The thermal expansion of capillary material was compensated by cleaving the one end of FBG free and the other end with the temperature resistant epoxy resins. Experiments results validate that the proposed method can successfully monitor the strain and temperature factors that can be applied to composite material at cryogenic temperatures.
Surface plasmon resonance effect in helical photonic crystal fiber using transformation optics formalism
Author(s):
Chen Li;
Li Xia;
Xin Chen
Show Abstract
By using a rigorous modeling method, the SPR properties in a helical PCF has been simulated for the first time and the resonance effects have been studied by using finite element method. The results show that spiral path will increase propagation loss, but resonance peak values of the spectrum decrease. This is due to a light dispersion away from the center core, causing the energy transfer reduction between fundamental mode and SPP modes. Therefore, in the design of photonic crystal fiber structure, the liquid channel should be placed outside of the cladding rather than at the core.
High accuracy demodulation for twin-grating based sensor network with hybrid TDM/FDM
Author(s):
Fan Ai;
Qizhen Sun;
Jianwei Cheng;
Yiyang Luo;
Zhijun Yan;
Deming Liu
Show Abstract
We demonstrate a high accuracy demodulation platform with a tunable Fabry-Perot filter (TFF) for twin-grating based fiber optic sensing network with hybrid TDM/FDM. The hybrid TDM/FDM scheme can improve the spatial resolution to centimeter but increases the requirement of high spectrum resolution. To realize the demodulation of the complex twin-grating spectrum, we adopt the TFF demodulation method and compensate the environmental temperature change and nonlinear effect through calibration FBGs. The performance of the demodulation module is tested by a temperature experiment. Spectrum resolution of 1pm is realized with precision of 2.5pm while the environmental temperature of TFF changes 9.3°C.
Distributed dual-parameter optical fiber sensor based on cascaded microfiber Fabry-Parot interferometers
Author(s):
Yang Xiang;
Yiyang Luo;
Wei Zhang;
Deming Liu;
Qizhen Sun
Show Abstract
We propose and demonstrate a distributed fiber sensor based on cascaded microfiber Fabry-Perot interferometers (MFPI) for simultaneous refractive index (SRI) and temperature measurement. By employing MFPI which is fabricated by taper-drawing the center of a uniform fiber Bragg grating (FBG) on standard fiber into a section of microfiber, dual parameters including SRI and temperature can be detected through demodulating the reflection spectrum of the MFPI. Further, wavelength-division-multiplexing (WDM) is applied to realize distributed dual-parameter fiber sensor by using cascaded MFPIs with different Bragg wavelengths. A prototype sensor system with 5 cascaded MFPIs is constructed to experimentally demonstrate the sensing performance.
Metal-organic framework thin films on a surface of optical fibre long period grating for chemical sensing
Author(s):
J. Hromadka;
B. Tokay;
S. James;
S. Korposh
Show Abstract
An optical fibre long period grating (LPG) modified with a thin film of HKUST-1, a material from metal organic framework (MOF) family, was employed for the detection of carbon dioxide. The sensing mechanism is based on the measurement of the change of the refractive index (RI) of the coating that is induced by the penetration of CO2 molecules into the HKUST-1 pores. The responses of the resonance bands in the transmission spectrum of an LPG modified with 40 layers of HKUST-1 upon exposure to carbon dioxide in mixture with nitrogen were investigated.
Fresnel-reflection-based fiber optic cryogenic temperature sensor
Author(s):
Umesh Sampath;
Dae-gil Kim;
Hyunjin Kim;
Minho Song
Show Abstract
In this paper, Fresnel reflection based fiber-optic sensor for the real-time monitoring of cryogenic temperature is presented. The proposed sensor system utilizes a linear thermo-optic coefficient of polymer and Fresnel reflection of the fiber end. Epoxy resin and poly methyl metha acrylate (PMMA) are used as sensor head material. The designed sensor head measures the temperature ranging from -180°C to 25°C with an average sensitivity of 0.039dB/°C for epoxy resin and 0.029dB/°C for PMMA. Experimental results have proven the stability and the effectiveness of the proposed sensor system to measure the applied cryogenic temperatures.
Comparison of different photoresist buffer layers in SPR sensors based on D-shaped POF and gold film
Author(s):
Nunzio Cennamo;
Maria Pesavento;
Letizia De Maria;
Ramona Galatus;
Francesco Mattiello;
Luigi Zeni
Show Abstract
A comparative analysis of two optical fiber sensing platforms is presented. The sensors are based on surface plasmon resonance (SPR) in a D–shaped plastic optical fiber (POF) with a photoresist buffer layer between the exposed POF core and the thin gold film. We show how the sensor's performances change when the photoresist layer changes. The photoresist layers proposed in this analysis are SU-8 3005 and S1813. The experimental results are congruent with the numerical studies and it is instrumental for chemical and bio-chemical applications. Usually, the photoresist layer is required in order to increase the performance of the SPR-POF sensor.
In vivo brain temperature measurements based on fiber optic Bragg grating
Author(s):
Mohammad I. Zibaii;
Hamid Latifi;
Fatemeh Karami;
Abdolaziz Ronaghi;
Sara Chavoshi Nejad;
Leila Dargahi
Show Abstract
This work reports on the development of an optical fiber sensor based fiber Bragg Grating (FBG) probe for in vivo measurements of brain temperature. The major goal of this work is to demonstrate that the changes in brain temperature induced by drugs is an important reality, which could provide new valuable information on the mechanisms of drug action and open new therapeutic approaches. This probe can be interrogated using a portable optical measurement setup, allowing for measurements to be performed outside of standard optical laboratories.
Fiber Bragg grating interrogation using a wavelength modulated 1651-nm tunable distributed feedback laser and a fiber ring resonator for wearable biomedical sensors
Author(s):
Anirban Roy;
Arup Lal Chakraborty;
Chandan Kumar Jha
Show Abstract
This paper demonstrates the interrogation of a fiber Bragg grating with a flat-topped reflection spectrum centred on 1649.55 nm using only a single mode tunable 1651.93 nm semiconductor laser and a fiber ring resonator. The Bragg shift is accurately measured with the fiber-optic ring resonator that has a free spectral range (FSR) of 0.1008 GHz and a broadband photo-detector. Laser wavelength modulation and harmonic detection are used to transform the gentle edges of the flat-topped FBG spectrum into prominent leading and trailing peaks, either of which can be used to accurately measure spectral shifts of the FBG reflection spectrum with a resolution of 0.9 pm. A Raspberry Pi-based low-cost embedded processor is used to measure the temperature-induced spectral shifts over the range 30˚C – 80˚C. The shift was linear with a temperature sensitivity of 12.8 pm/˚C. This technique does not use an optical spectrum analyzer at any stage of its design or operation. The laser does not need to be pre-characterized either. This technique can be readily extended to all types of tunable diode lasers and is ideally suited for compact field instruments.
Active polymer materials for optical fiber CO2 sensors
Author(s):
Karol Wysokiński;
Marta Filipowicz;
Tomasz Stańczyk;
Stanisław Lipiński;
Marek Napierała;
Michał Murawski;
Tomasz Nasiłowski
Show Abstract
CO2 optical fiber sensors based on polymer active materials are presented in this paper. Ethyl cellulose was proven to be a good candidate for a matrix material of the sensor, since it gives porous, thick and very sensitive layers. Low-cost sensors based on polymer optical fibers have been elaborated. Sensors have been examined for their sensitivity to CO2, temperature and humidity. Response time during cyclic exposures to CO2 have been also determined. Special layers exhibiting irreversible change of color during exposure to carbon dioxide have been developed. They have been verified for a possible use in smart food packaging.
Liquid droplet sensing using twisted optical fiber couplers fabricated by hydrofluoric acid flow etching
Author(s):
Gyeongho Son;
Youngho Jung;
Kyoungsik Yu
Show Abstract
We report a directional-coupler-based refractive index sensor and its cost-effective fabrication method using hydrofluoric acid droplet wet-etching and surface-tension-driven liquid flows. The proposed fiber sensor consists of a pair of twisted tapered optical fibers with low excess losses. The fiber cores in the etched microfiber region are exposed to the surrounding medium for efficient interaction with the guided light. We observe that the etching-based low-loss fiber-optic sensors can measure the water droplet volume by detecting the refractive index changes of the surrounding medium around the etched fiber core region.
Dynamic measurements of physical quantities in extreme environment using fiber Bragg grating
Author(s):
Y. Barbarin;
A. Lefrançois;
S. Magne;
V. Chuzeville;
M. Balbarie;
L. Jacquet;
F. Sinatti;
A. Osmont;
J. Luc
Show Abstract
Fiber Bragg Gratings (FBGs) are used to measure shock velocity, detonation velocity, shock wave profile or pressure profile in inert and energetic materials. Such thin probe, with a diameter below 150 μm, can be inserted directly into materials without disturbing the physical phenomena. Chirped FBGs are used to track the shock wave in the grating using wavelengths. The velocity (few km/s) and shock wave profile measurements are realized by recording the CFBG’s reflected spectral width. Pressure measurements at few GPa levels use dynamic spectrometers, two approaches are compared: parallel acquisition using an Arrayed-Waveguide-Grating and time-multiplexing by wavelength-to-time conversion using dispersion.
Plane-by-plane inscription of grating structures in optical fibers
Author(s):
P. Lu;
S. J. Mihailov;
H. Ding;
D. Grobnic;
R. Walker;
D. Coulas;
C. Hnatovsky;
A. Y. Naumov
Show Abstract
Plane-by-plane fabrication of fiber Bragg gratings in optical fibers using short-pulse femtosecond IR laser is proposed and demonstrated. By incorporating a cylindrical lens in the fabrication setup, a plane of index modification can be directly inscribed in fiber core by a single laser pulse through the proposed method. This plane-by-plane method simplifies the grating inscription process and allows for the fabrication of complicated grating structures.
Adiabatic tapered optical fiber Fabry-Perot structure as a refractive index sensor
Author(s):
O. R. Ranjbar-Naeini;
Z. Chenari;
P. Zarafshani;
F. Jafari;
H. Latifi
Show Abstract
In this article, an Adiabatic Tapered Optical Fiber -- Fabry Perot (ATOF-FP) Sensor is introduced as a simple refractive index sensor. This FP Cavity relies upon reflection from two cleave ends of ATOF sensor’s arms. Its spectrum was investigated with Distributed Feedback (DFB) tunable laser and photo detector. With analyzing the change in Optical Transmission Power (OTP) versus refractive index changes, the sensitivity of ATOF was -66.21 dB/RIU. In addition, the visibility of FP was studied. Its RI sensitivity was -0.975 1/RIU. The sensor resolution was 2.3 × 10-5 RIU with consideration of minimum detectable signal of acquisition system.
Precise measurement technique of long period fiber grating sensors using Fourier transform method
Author(s):
Mayumi Nagatsuka;
Masayoshi Koizumi;
Satoshi Tanaka;
Atsushi Wada;
Nobuaki Takahashi
Show Abstract
A precise measurement technique of long period of fiber grating sensor (LPG) is demonstrated by employing a cascaded chirp LPG (C-CLPG) as a sensing device and by adopting a Fourier transform method for an interrogation technique. In this approach, transmittance of the C-CLPG exhibits periodic channeled spectrum and its strain- and/or temperature-dependent wavelength shift is analyzed by obtaining a cross-spectrum function between the original and the shifted channeled spectra, in which the phase term of the cross-spectrum corresponds to the wavelength shift. Since the phase component is determined by using all the channeled spectrum over a wider bandwidth of the C-CLPG, more precise measurements of the strain and temperature are expected than that of the peak search method in that the wavelength shift is determined by the shift of one of peaks of the channeled spectrum. In the experiment, the highly precise strain and temperature measurements are presented by comparing with the results of the peak search method.
Highly sensitive temperature sensor using intrinsic Mach-Zehnder interferometer formed by bent micro-fiber embedded in polymer
Author(s):
Pathi Munendhar;
Lei Zhang;
Limin Tong;
Shaoliang Yu
Show Abstract
We reported a simple, robust, and highly sensitive temperature sensor using intrinsic Mach-Zehnder interferometer formed by means of bending a tapered microfiber, embedded in polydimethylsiloxane. The outer temperature perturbations modulate the refractive index of the polymer through thermo-optic and thermal expansion effects of the polymer. This leads to a phase difference between interfering guided modes through the bent-microfiber, which ultimately results prominent wavelength shift in the transmission spectrum. The sensor exhibits a linear temperature response with a sensitivity as high as -6.25nm/°C over the temperature range from 24° to 40 °C. The sensitivity of the sensor increases as wavelength increases.
Ultra-sensitive wide dynamic range temperature sensor based on in-fiber Lyot interferometer
Author(s):
Hamed Nikbakht;
Mohamad Hosein Poorghdiri Isfahani;
Hamid Latifi
Show Abstract
An in-fiber Lyot interferometer for temperature measurement is presented. The sensor utilizes high temperature-dependence of the birefringence in Panda polarization maintaining fibers to achieve high resolution in temperature measurements. Temperature variation modulates the phase difference between the polarization modes propagating in different modes of the Panda fiber. The Lyot interferometer produces a spectrum which varies with the phase difference. Therefore, by monitoring this spectrum a high resolution of 0.003°C was achieved. A fiber Bragg grating is added to the setup to expand its dynamic range. This sensor does not need complicated fabrication process and can be implemented in many applications.
Analysis of signal saturation in a fiber ring resonator integrating an intensity sensor
Author(s):
Regina Magalhães;
Susana O. Silva;
Orlando Frazão
Show Abstract
The proposed technique consists in an optical fiber resonator interrogated for sensor characterization, implementing an alternative technique for dynamic range improvement. Such technique relies on the analysis of an added-signal caused by signal saturation, which occurs due to the broadening of the laser pulse. A wide study for different pulse widths is presented in this work, namely for 100 ns, 5 μs and 20 μs, being the last one related to the emergence of an added-signal for the proposed configuration. The behavior of the waveform in the presence of an intensity sensor is also characterized.
Effects of pre-strain on the intrinsic pressure sensitivity of polymer optical fiber Bragg gratings
Author(s):
Jens Kristian Mølgaard Pedersen;
Getinet Woyessa;
Kristian Nielsen;
Ole Bang
Show Abstract
We experimentally demonstrate a scheme for improving the intrinsic pressure sensitivity of fiber Bragg-gratings (FBGs) inscribed in polymer optical fibers by applying pre-strain in order to suppress the pressure induced mechanical contraction of the fiber. This contraction would otherwise contribute to a blueshift of the Brag-wavelength, counteracting the dominant redshift caused by the stress-optic effect, which effectively reduces the pressure sensitivity of the FBG. By applying this technique we are able to improve the sensitivity of the FBG from 2.8 pm/bar to 7.3 pm/bar.
Optical power-based interrogation of plasmonic tilted fiber Bragg grating biosensors
Author(s):
Á. González-Vila;
A. Lopez-Aldaba;
D. Kinet;
P. Mégret;
M. Lopez-Amo;
C. Caucheteur
Show Abstract
Two interrogation techniques for plasmonic tilted fiber Bragg grating sensors are reported and experimentally tested. Typical interrogation methods are usually based on tracking the wavelength shift of the most sensitive cladding mode, but for biosensing applications, spectrometer-based methods can be replaced by more efficient solutions. The proposed techniques thus rely on the measurement of the induced changes in optical power. The first one consists of a properly polarized tunable laser source set to emit at the wavelength of the sensor most sensitive mode and an optical power meter to measure the transmitted response. For the second method, a uniform fiber Bragg grating is photo-inscribed beyond the sensor in such a way that its central wavelength matches the sensor most sensitive mode, acting as an optical filter. Using a LED source, light reflected backwards by this grating is partially attenuated when passing through the sensor due to plasmon wave excitation and the power changes are quantified once again with an optical power meter. A performance analysis of the techniques is carried out and they both result competitive interrogation solutions. The work thus focuses on the development of cost-effective alternatives for monitoring this kind of biosensors in practical situations.
Optical monitoring of thin film electro-polymerization on surface of ITO-coated lossy-mode resonance sensor
Author(s):
Michał Sobaszek;
Magdalena Dominik;
Dariusz Burnat;
Robert Bogdanowicz;
Viteszlav Stranak;
Petr Sezemsky;
Mateusz Śmietana
Show Abstract
This work presents an optical fiber sensors based on lossy–mode resonance (LMR) phenomenon supported by indium tin oxide (ITO) thin overlay for investigation of electro-polymerization effect on ITO’s surface. The ITO overlays were deposited on core of polymer-clad silica (PCS) fibers using reactive magnetron sputtering (RMS) method. Since ITO is electrically conductive and electrochemically active it can be used as a working electrode in 3-electrode cyclic voltammetry setup. For fixed potential applied to the electrode current flow decrease with time what corresponds to polymer layer formation on the ITO surface. Since LMR phenomenon depends on optical properties in proximity of the ITO surface, polymer layer formation can be monitored optically in real time. The electrodeposition process has been performed with Isatin which is a strong endogenous neurochemical regulator in humans as it is a metabolic derivative of adrenaline. It was found that optical detection of Isatin is possible in the proposed configuration.
Double resonance long period fiber grating for detection of E. coli in trace concentration by choosing a proper bacteriophage
Author(s):
Y. Chiniforooshan;
A. Celebanska;
M. Janik;
P. Mikulic;
F. Haddad;
J. Perreault;
W. J. Bock
Show Abstract
There is a critical need of a fast, specific and reliable assay for biological species. To address this need, long period fiber gratings (LPFG) among other fiber optic sensors can be used because of their high sensitivity to changes in surrounding medium. In this work we fabricated and used two over-etched LPFGs. One of them was covered with T4 Phage and the other was covered with MS2 phage that both specifically bind with Escherichia coli (E. coli) bacteria. This bacterium is a major cause of the food contaminations and outbreaks. We showed achieving a highest sensitivity region of the LPFG and the way to fine tune to that region by over-etching the grating. Finally, using the highly sensitive LPFG platform we could detect E. coli at concentrations as low as 100 colony forming units (CFU), by covering the LPFG with an optimized bio-functionalization of the fiber surface with MS2 bacteriophage.
Development of a high resolution optical-fiber tilt sensor by F-P filter
Author(s):
Jianjun Pan;
Qiuming Nan;
Shujie Li;
Zhonghua Hao
Show Abstract
A high-resolution tilt sensor is developed, which is composed of a pair of optical fiber collimators and a simple pendulum with an F-P filter. The tilt angle is measured by demodulating the shift of center wavelength of F-P filter, which is caused by incidence angle changing. The relationship between tilted angle and the center wavelength is deduced. Calibration experiment results also confirm the deduction, and show that it is easy to obtain a high resolution. Setting the initial angle to 6degree, the measurement range is ±3degree, its average sensitivity is 1104pm/degree, and its average resolution is as high as 0.0009degree.
Two-dimensional array of plasmonic V-shaped grooves for sensing applications
Author(s):
Hyeonsoo Park;
Kyookeun Lee;
Jeong-Geun Yun;
Chulsoo Choi;
Hwi Kim;
Byoungho Lee
Show Abstract
We numerically analyzed the refractive index sensing performance of the two-dimensional array of plasmonic V-shaped grooves. The structural parameters are optimized to show a sharp and large reflectance dip with desired sensing region (n=1.33). Acquiring the sensitivity of the environmental refractive index as 400 nm/RIU in the visible region, FWHM of the dip is ~5 nm. It shows that the proposed structure has extreme value of quality factor and good extinction ratio. The localized mode has the hot spot at the bottom of the grooves so that localized sensing based on magnetic field enhancement is possible. Moreover, the localized mode is dependent on the tapered angle of the grooves, not the opening ratio. The performance of the dual V-shaped grooves is also discussed. The array of the closely located grooves has nearly identical reflectance spectra but a moderate amount of dip shift exists. As well as obtaining refractive index sensing by this configuration, magnetic field hot spot generation by coherent excitation can be applied to highly localized sensing and enhancing nonlinear processes.
Refractive index sensor using layered nanoslit array based on Fabry-Pérot resonances
Author(s):
Jangwoon Sung;
Joonsoo Kim;
Jongwoo Hong;
Yohan Lee;
Byoungho Lee
Show Abstract
We proposed a refractive index sensor using a phase-compensated cavity whose resonant wavelength can be tuned by the alignment between layers. The structures are composed of double-layered nanoslit array, which has total thickness of 100 nm while the cavity length is 30 nm thick. Using nanoslit array as a reflector has made it possible to design the phase shift carefully so that the subwavelength Fabry-Pérot cavity can be obtained. When the cavity is filled with sensing medium, where the field enhancement is achieved by Fabry-Pérot (FP) resonance, the proposed structure is found to achieve sensitivity ranging from 337 nm/RIU to 1250 nm/RIU at each different alignment. The resonant wavelength ranges from 1100 nm to 2500 nm, which contains biological windows and telecommunication wavelength range, so the structure is expected to be used in various purposes.
Multiplexed sub-nano resolution quasi-static strain sensor based on transient response of Fabry-Perot interferometers
Author(s):
Jiageng Chen;
Qingwen Liu;
Zuyuan He
Show Abstract
We present a multiplexed quasi-static strain sensor with sub-nano resolution using fiber Fabry-Perot interferometers (FFPIs). The FFPIs are connected in ladder structure with cascaded couplers and delay fibers for multiplexing, and their transient response excited by laser pulses are acquired to distinguish the resonant frequencies of each FFPI. An electro-optical system based on acousto-optic modulator is employed to interrogate the sensor array. In the demonstrational experiment, 3-channel strain measurement with resolutions better than 0.2 nε/Hz1/2 in frequency band from 0.1 Hz to 100 Hz is realized.
DNA based thin solid films and its application to optical fiber temperature sensor
Author(s):
Seongjin Hong;
Woohyun Jung;
Taeoh Kim;
Kyunghwan Oh
Show Abstract
Temperature dependent refractive index of DNA-cetyltrimethylammonium chloride (CTMA) thin-solid-film was measured 20 to 90℃ to obtain its thermo-optic coefficient of -3.6×10-4 (dn/dT). DNA- CTMA film has high thermosoptic coefficient than other polymers. The film was deposited on coreless silica fiber (CSF) to serve as a multimode interferometer optical fiber temperature sensor. It is immersed in a water that changed temperature from 40 to 90℃. It has sensitivity of 0.25nm/℃.
MOPA fiber laser for photoacoustic imaging using arrayed ultrasound transducer
Author(s):
Yong-Jae Lee;
Jun-Tae Ahn;
Eun-Ju Jeong;
Hyun-Woo Song;
Chang-Geun Ahn;
Hyung Wook Noh;
Joo Yong Sim;
Min Yong Jeon;
Susung Lee;
Bong Kyu Kim
Show Abstract
An Nd:YAG laser is generally used as the optical source for photoacoustic imaging (PAI) systems, which support a high-power pulsed laser. However, PAI systems based on Nd:YAG lasers have several disadvantages, such as instability against impact and vibration, poor mobility, and large size. To overcome the limitations, we demonstrate a PAI system using a master oscillator power amplifier (MOPA) fiber laser and an arrayed ultrasound transducer. The fabricated MOPA fiber laser has a variable repetition rate in the range of 1–50 kHz, a pulse width of 10–70 ns, and an output power of 160 μJ. Furthermore, it is stable to impact and vibration, mobile, and compact with a size of 427×250×170 mm3. We achieved PAI 150 times faster using MOPA fiber laser than using Nd:YAG laser with the arrayed ultrasound transducer composed of 128 elements. Therefore, we believe that the PAI system based on the MOPA fiber laser has significant potential for use as a clinical ultrasound imaging system.
Locally pressed plastic optical fibers for refractive index sensing
Author(s):
Shumpei Shimada;
Heeyoung Lee;
Makoto Shizuka;
Hiroki Tanaka;
Neisei Hayashi;
Yosuke Mizuno;
Kentaro Nakamura
Show Abstract
Power-based refractive index (RI) sensing is demonstrated by exploiting an ultrasonically pressed plastic optical fiber (POF). We can be easily and cost-efficiently fabricate this structure, within a short while ( ~1 s), without using external heat sources or chemical materials. We have only to simply press the horn connected to an ultrasonic transducer against part of the POF. The RI dependence of the transmitted power exhibits linear trends in the RI ranges from ~1.32 to ~1.36 (coefficient: −62 dB/RIU (RI unit)) and ~1.40 to ~1.44 (coefficient: −257 dB/RIU)). We also study the temperature dependence of the transmitted power.
High sensitive FBG load cell for icing of overhead transmission lines
Author(s):
Naiqiang Mao;
Guoming Ma;
Chengrong Li;
Yabo Li;
Cheng Shi;
Yue Du
Show Abstract
Heavy ice coating of overhead transmission lines created the serious threat on the safe operation of power grid. The measurement of conductor icing had been an effective and reliable methods to prevent potential risks, such as conductor breakage, insulator flashover and tower collapse. Because of the advantages of immunity to electromagnetic interference and no demand for power supply in site, the optical load cell has been widely applied in monitoring the ice coating of overhead transmission lines. In this paper, we have adopted the shearing structure with additional grooves as elastic element of load cell to detect the eccentric load. Then, two welding package fiber Bragg gratings (FBGs) were mounted onto the grooves of elastic element with a direction deviation of 90° to eliminate temperature effects on strain measurement without extra FBG. After that, to avoid the occurrence of load cell breakage in heavy load measurement, the protection part has been proposed and added to the elastic element. The results of tension experiments indicate that the resolution of the load cell is 7.78 N in the conventional measuring range (0–10 kN). And in addition, the load cell proposed in this paper also has a good performance in actual experiment in which the load and temperature change simultaneously.
A novel single fiber optical tweezers based on GIMMF: simulation and experiment
Author(s):
Tong Wang;
Xiaoyun Tang;
Yaxun Zhang;
Yu Zhang;
Zhihai Liu
Show Abstract
We propose a novel single fiber optical tweezers based on a graded-index multimode fiber (GIMMF), whose length is arbitrary (when the length is larger than 5mm). The optical fiber tweezers based on GIMMFs can propagate larger light field intensity and trap particles easily. The optical fiber tweezers based on precise length GIMMF had been achieved. In this paper, the optical fiber tweezers applies the GIMMF with arbitrary length, which ensure the fabrication of the optical tweezers based on the GIMMF simple, convenient and repeatability.
A light intensity monitoring method based on fiber Bragg grating sensing technology and BP neural network
Author(s):
Lu-Ming Li;
Qian Zhu;
Zhi-Guo Zhang;
Zhi-Min Cai;
Zhi-Jun Liao;
Zhen-Yan Hu
Show Abstract
In this paper, a light intensity monitoring method based on FBG is proposed. The method establishes a light intensity monitoring model with cantilever beam structure and BP neural network algorithm, which is based on fiber grating sensing technology. The accuracy of the model can meet the requirements of engineering project and it can monitor light intensity in real time. The experimental results show that the method has good stability and high sensitivity.
On the actual bandwidth of some dynamic fiber optic strain/temperature interrogators
Author(s):
Rotem R. Preizler;
R. Davidi;
Avi Motil;
Yakov Botsev;
Meir Hahami;
Moshe Tur
Show Abstract
The measurement accuracy of dynamic fiber-optic sensing interrogators, which use frequency scanning to determine the value of the measured, err as either the event bandwidth approaches half the instrument sampling frequency or when the event dynamic range comes close to the instrument designed value. One main source of error is the common practice of assigning sampling at a non-uniform grid to a uniform one. Harmonics higher than -20 dB are observed for signal frequencies exceeding 25% of the sampling rate and/or for signal amplitudes higher than 15% of the instrument dynamic range. These findings have applications to fiber-Bragg-grating and Brillouin interrogators.
A highly sensitive twist sensor without temperature cross sensitivity based on tapered single-thin-single fiber offset structure
Author(s):
Wenjun Ni;
Ping Lu;
Deming Liu;
Jiangshan Zhang;
Shibin Jiang
Show Abstract
A highly sensitive twist sensor without temperature cross sensitivity based on tapered single mode-thin core-single mode fiber offset structure is proposed and experimentally demonstrated. The two parameters mentioned above can be measured simultaneously without cross sensitivity. The twist sensitivity of 0.12dB/° is achieved by tracking power variation of the resonant wavelength, and the wavelength shift of the spectrum is ±0.01nm. The temperature sensitivity of 0.12nm/°C can be achieved by wavelength demodulation, and the power fluctuation of the spectrum is ±0.015dB. Therefore, the twist and temperature can be detected by the power and wavelength demodulation method, respectively.
Hollow glass microsphere-structured Fabry-Perot interferometric sensor for highly sensitive temperature measurement
Author(s):
Junna Cheng;
Ciming Zhou;
Dian Fan;
Yiwen Ou
Show Abstract
We propose and demonstrate a miniature Fabry-Perot (F-P) interferometric sensor based on a hollow glass microsphere (HGM) for highly sensitive temperature measurement. The sensor head is fabricated by sticking a HGM on the end face of a single-mode fiber, and it consists of a short air F-P cavity between the front and the rear surfaces of the HGM. A sensor with 135.7280-μm cavity length was tested for temperature measurement from -5 °C to 50 °C. The obtained sensitivity reached up to 24.5 pm/°C and the variation rate of the HGM- F-P’s cavity length was2.1 nm/°C. The advantages of compact size, easy fabrication and low cost make the sensor suitable for highly sensitive temperature sensing.
Polyaniline deposition on tilted fiber Bragg grating for pH sensing
Author(s):
A. Lopez Aldaba;
Á. González-Vila;
M. Debliquy;
M. Lopez-Amo;
C. Caucheteur;
D. Lahem
Show Abstract
In this paper, we present the results of a new pH sensor based on a polyaniline (PAni) coating on the surface of a tilted fiber Bragg grating. The pH-sensitive PAni was deposited by in situ chemical oxidative polymerization. The performance of the fabricated pH sensor was tested and the obtained pH values were compared with the results obtained using a pH meter device. It was found that the sensor exhibits response to pH changes in the range of 2-12, achieving a sensitivity of 46 pm/pH with a maximum error due to the hysteresis effect of ±1.14 pH. The main advantages of this PAni-TFBG pH sensor are biochemical compatibility, temperature independence, long-term stability and remote realtime multipoint sensing features. This type of sensor could be used for biochemical applications, pipeline corrosion monitoring or remote-multipoint measurements.
Ultrafast laser-induced negative-index fiber Bragg gratings with enhanced thermal stability
Author(s):
Jun He;
Changrui Liao;
Kaiming Yang;
Yiping Wang
Show Abstract
Negative-index fiber Bragg gratings (FBGs) were fabricated using 800 nm femtosecond laser overexposure and thermal regeneration. A positive-index type I-IR FBG was first inscribed in H2-free fiber with a uniform phase mask, and then a highly polarization dependent phase-shifted FBG (PSFBG) was created from the type I-IR FBG by overexposure. Subsequently, the PSFBG was annealed at 800 °C for 12 hours. A negative-index FBG was obtained with a reflectivity of 99.22%, an insertion loss of 0.08 dB, a blue-shift of 0.83 nm, and an operating temperature of up to 1000 °C.
Accurate reconstruction of digital holography using frequency domain zero padding
Author(s):
Jun Geun Shin;
Ju Wan Kim;
Jae Hwi Lee;
Byeong Ha Lee
Show Abstract
We propose an image reconstruction method of digital holography for getting more accurate reconstruction. Digital holography provides both the light amplitude and the phase of a specimen through recording the interferogram. Since the Fresenl diffraction can be efficiently implemented by the Fourier transform, zero padding technique can be applied to obtain more accurate information. In this work, we report the method of frequency domain zero padding (FDZP). Both in computer-simulation and in experiment made with a USAF 1951 resolution chart and target, the FDZD gave the more accurate rconstruction images. Even though, the FDZD asks more processing time, with the help of graphics processing unit (GPU), it can find good applications in digital holography for 3-D profile imaging.
Noncontact measurement of elasticity using optical fiber-based heterodyne interferometer and laser ultrasonics
Author(s):
Jonghyun Eom;
Soongho Park;
Jinwoo Lee;
Byeong Ha Lee
Show Abstract
We propose the noncontact measurement of elasticity by using an optical fiber heterodyne interferometer and laser ultrasonics. The surface acoustic wave (SAW), that is generated by the laser pulse irradiation on the sample surface and propagating along the surface, is optically monitored by the heterodyne interferometer without taking any contact with the sample. By taking several measurements with changing the relative distance between the excitation and the measurement points, the phase velocity of SAW was calculated and from which the elasticity of the sample could be obtained. This proposed method was experimentally evaluated by using PDMS samples having various mixing ratio of curing agent and PDMS. For the sample of a 12:1 mixing ratio, the phase velocity was measured as about 39.46 m/s and the Young’s modulus as about 1987 kPa. This technique is expected to detect the mechanical properties of biological tissues also.
Refractive index sensor based on helical long period grating based on dual-hole elliptical core fiber
Author(s):
Chao Liu;
Yu Zhang;
Zhihai Liu;
Yaxun Zhang
Show Abstract
In this paper, the fabrication of a novel refractive index sensor based on helical long period grating (HLPG) written in a dual-hole elliptical core fiber (DHECF) was demonstrated and the sensing characteristic was experimentally investigated. Due to the structure of the DHECF, The proposed HLPG sensor could work with ultra-small dose testing samples. In addition, since the sample is isolated from the external environment, the testing is immunity to the external interference. The experimental results showed that the testing sensitivity of the sensor was 194nm/RIU with the refractive index range of 1.333 to 1.385. The proposed structure will have a good practicability in the microfluidic sensing system.
Polarization stable plasmonic sensor based on tilted fiber Bragg grating
Author(s):
Kirill A. Tomyshev;
Yuriy K. Chamorovskiy;
Vasily E. Ustimchik;
Oleg V. Butov
Show Abstract
This paper presents a solution to one of the major problems of plasmonic fiber Bragg grating sensors concerning their high sensitivity to changes in the polarization state of light propagating through optical fiber. For the first time these kind of sensors have been produced using polarization maintaining fibers, thereby stabilization has been achieved using mechanical action and bending the supplied fiber. Comparative experiments have demonstrated that the sensor readings stability is at least an order of magnitude higher relative to other sensors, which record in a standard fiber with an isotropic structure.
High speed strain measurement of active mode locking FBG laser sensor using chirped FBG cavity
Author(s):
Gyeong Hun Kim;
Joon Young Kim;
Chang Hyun Park;
Chang-Seok Kim;
Hwi Don Lee;
Youngjoo Chung
Show Abstract
We propose a high speed strain measurement method using an active mode locking (AML) fiber Bragg grating (FBG) laser sensor with a chirped FBG cavity. The mode-locked frequency of the AML laser depends on both the position and Bragg wavelength of the FBG. Thus, the mode-locked frequency of cascaded FBGs can be detected independently along the cavity length of cascaded FBGs. The strain across FBGs can be interrogated dynamically by monitoring the change in mode-locked frequency. In this respect, the chirped FBG critically improves the frequency sensitivity to Bragg wavelength shift as a function of increasing dispersion in the AML cavity. The strain measurement of the FBG sensor shows a highly linear response, with an R-squared value of 0.9997.
Quantum wires as sensors of the electric field: a model into quantum plasmonics
Author(s):
R. A. Alves;
J. C. Costa;
M. Gomes;
Nuno A. Silva;
A. Guerreiro
Show Abstract
This paper presents a study for a fibre optic sensor based on quantum wires to detect and measure the amplitude and direction of a static electric field. This study is supported by the analogy of the fluid equations describing the free electrons in the quantum wires and the Madelung formalism of Quantum Mechanics. In this context, it is possible to construct a diatomic plasmonic molecule whose energy levels can be Stark shifted by an external electric field and readout using a light beam tuned to the Rabi oscillations of these levels. Choosing the adequate design parameters it is possible to estimate a sensitivity of 100nm/NC-1.
Calibration and uncertainty of a fibre optic measurement system for Fresnel reflectometer sensors
Author(s):
Jonathan Oelhafen;
Tobias Mayr;
Konstantinos Moutzouris;
Johannes Roths;
Klaus Drechsler
Show Abstract
A four-channel fibre optic measurement system for fibre Bragg grating (FBG) sensors was used to measure the refractive index of fluids with Fresnel reflectometer sensors prepared from SMF28e singlemode fibres. The fibre optic measurement system was calibrated with five high-purity organic fluid samples in the refractive index range between 1.3 and 1.6. The light source had a wavelength of 1550 nm and the fluid samples were held at 24 °C. In total, 400 refractive index measurements were performed. The calibration of the fibre optic measurement system was performed with a linear correction function. The combined uncertainty of the refractive index measurements with the fibre optic measurement system was found to be in the order of 10-4.
Research on multi-physics field factors and data driven model of giant magnetostrictive actuator based on FBG sensors
Author(s):
Ping Han;
GuanLin Du
Show Abstract
The Fiber Bragg Grating(FBG) sensors are applied to Giant Magnetostrictive Actuator(GMA) to obtain the multi-physics field factors, which are the basis of data driven model. The real working circumstance of GMA is complex and nonlinear, and the traditional theoretical physics model of GMA cannot satisfy it. Hence, the multi-physics field factors of the components of GMA in real working process are gathered real-time by FBG sensors, such as temperature of Giant Magnetostrictive Material(GMM) stick and coil, displacement and vibration of GMM stick, current of coil etc, which are utilized to represent the strong nonlinear characteristics of GMA. Furthermore, the data driven model of GMA is built with the Least Squares Support Vector Machine(LS-SVM) method based on multi-physics field factors. The performance of the novel GMA model is evaluated by experiment, its maximum error is 1.1% with frequency range from 0 to 1000Hz and temperature range from 20°C to 100°C.
Distributed Brillouin optical fiber sensing for dynamic strain with frequency agility based on dual-modulation
Author(s):
Dexin Ba;
Dengwang Zhou;
Benzhang Wang;
Mingjing Yin;
Yongkang Dong;
Zhiwei Lu;
Zhigang Fan
Show Abstract
A dynamic distributed Brillouin optical fiber sensing based on dual-modulation is proposed, in which the scanning of the Brillouin gain spectrum (BGS) is implemented by the combination of a single-frequency modulation and a frequency-agility modulation. The frequency of the single-frequency modulation is a little less than the Brillouin frequency shift of the fiber (∼10.8 GHz for silica fiber), while the tuning range of the frequency-agility modulation is required to cover only several-hundred MHz for the scanning of BGS, which can significantly reduce the bandwidth requirement for the arbitrary waveform generator and ultimately reduce the cost of dynamic Brillouin sensors. With a 30-m fiber, a 11.8-Hz strain is measured. The spatial resolution and the sampling rate are 1 m and 200 Hz, respectively.
Ultrasonic imaging of seismic physical models using fiber Bragg grating Fabry-Perot probe
Author(s):
Ruixiang Zhou;
Xunli Yin;
Xueguang Qiao
Show Abstract
A fiber-optic sensor has been proposed and demonstrated for the ultrasonic wave (UW) imaging of seismic physical models. The sensor probe comprises a fiber Bragg grating Fabry-Perot (FBG-FP) mounted inside the tip of an aluminum cone focusing the UW into the fiber. The FBG-FP probe possesses an excellent UW sensitivity because of the narrowband notches on the top of the reflection spectrum caused by the Fabry-Perot (FP) interference. Because of the symmetrical structure of the sensor, it provides a directional UW detection with a high signal-to-noise ratio. As expected, the two-dimensional (2D) images of two physical models are reconstructed.
A novel orthogonal grating inscribed over inner cladding of a multi-cladding fiber
Author(s):
Weijia Bao;
Xueguang Qiao;
Qiangzhou Rong
Show Abstract
A novel orthogonal grating has been proposed and demonstrated. The grating is inscribed over inner cladding of a multi-cladding fiber containing two orthogonally cascaded “cladding” fiber Bragg gratings. Femtosecond laser side-illumination technique is utilized to ensure the two grating inscriptions are precisely positioned and compact in size. With such configuration, two pairs of well-defined cladding resonances have been achieved in reflection, which are originated from the internal cladding (two weakened resonances at shorter wavelength side) and from the fiber core (two stronger resonances at longer wavelength side), respectively. Most importantly, the “cladding” resonances are strongly directional sensitive to the small-vibration.
Optofluidic microring flowmeter based on heat transfer effect
Author(s):
Yuan Gong;
Minglei Zhang;
Chaoyang Gong;
Yu Wu;
Yunjiang Rao;
Xudong Fan
Show Abstract
We demonstrate an optofluidic flow rate sensor based on the heat transfer effect in a microfluidic channel for the lab-on-a-chip applications. By employing an optofluidic ring resonator (OFRR), the wavelength shift of the resonant dip of the whispering gallery mode is detected as a function of the flow rate when the flow is heated by a 1480 nm laser. A measurement range of 2 μL/min - 100 μL/min, a minimum detectable change of 30 nL/min for the flow rate detection are achieved. Experimental results indicate that the OFRR flow rate sensor has good repeatability and the inverse sensitivity is beneficial for detecting the low flow rate with high sensitivity.
Simultaneous temperature and vibration monitoring using an all-PM fiber loop mirror interferometer
Author(s):
D. Leandro;
M. Lopez-Amo
Show Abstract
In this work, an all-polarization maintaining fiber loop mirror interferometer is presented and validated as vibration and temperature sensor without crosstalk between measurands. The system is entirely built using polarization-maintaining (PM) fiber and a PM optical coupler. As a consequence, no polarization controllers are needed in the cavity, significantly simplifying the operation of the system and improving the stability and accuracy of the measurements. The loop comprises three PM fiber sections appropriately fused with an angle offset between them. In this manner, the interference is maximized and the sensing contributions of the two PM fibers used as communications channels are suppressed. The third PM fiber is used as the sensor itself, simultaneously monitoring temperature and mechanical vibration up to 1.2 kHz by means of an interrogation technique based on fast Fourier transform.
Code length limit in phase-sensitive OTDR using ultralong (>1M bits) pulse sequences due to fading induced by fiber optical path drifts
Author(s):
H. F. Martins;
K. Shi;
B. C. Thomsen;
S. Martin-Lopez;
M. Gonzalez-Herraez;
S. J. Savory
Show Abstract
Recently, it has been demonstrated that by recovering the amplitude and phase of the backscattered optical signal, a ΦOTDR using pulse coding can be treated as a fully linear system in terms of trace coding/decoding, thus allowing for the use of tens of thousands of bits with a dramatic improvement of the system performance. In this communication, as a continuation of previous work by the same authors, a preliminary study aiming at characterizing the limits of the system in terms of maximum usable code length is presented. Using a code exceeding 1million bits over a duration of 0.26ms, it is observed that fiber optical path variations exceeding ≈π occurring over a time inferior to the pulse code length can lead to localized fading in the ΦOTDR trace. The occurrence, positions and form of the fading points along the ΦOTDR trace is observed to be strongly dependent on the type, frequency and amplitude of the perturbations applied to the fiber.
Quasiperiodic nanohole array plasmonic sensors on optical fibers
Author(s):
P. Jia;
Z. Yang;
J. Yang;
H. Ebendorff-Heidepriem
Show Abstract
Surface plasmon resonance has found plenty of sensing applications on various platforms from label-free biosensing to surface-enhanced spectroscopies. Quasiperiodic nanohole arrays with patterns such as the Penrose tiling have been demonstrated with surface plasmon resonance enhanced optical transmission. Here we transfer quasiperiodic nanohole arrays onto optical fibers and measure their optical performance in refractive index sensing. These quasiperiodic arrays show multiple and narrow resonances related to their geometric features. These resonances are high sensitive to the dielectric changes on the probe surface due to our high quality fabrication. The sensitivity of quasiperiodic nanohole arrays is comparable to that of periodic nanohole arrays and reaches the theoretical sensitivity limit as predicted by our universal sensitivity analysis. This result verifies our sensitivity theory on propagating surface plasmon resonance in a wider range beyond periodic nanostructure arrays. Our study demonstrates the quasiperiodic nanohole array based optical fiber is a high-performance plasmonic sensor.
Simplex coded polarization optical time domain reflectometry system
Author(s):
Chaodong Wang;
Lihai Liu;
Wenbo Chen;
Ruolin Liao;
Ming Tang;
Songnian Fu
Show Abstract
In polarization optical time domain reflectometry (POTDR) system, the performance of polarimetric measurement is largely constrained by the low signal to noise ratio (SNR) due to the weak Rayleigh backscattering and the degradation of the degree of polarization (DOP) of signal light. It will be indispensable to improve the SNR without sacrificing the DOP of backscattered signal for a sufficient dynamic range. In this paper, a Simplex coded POTDR (sc-POTDR) system was proposed and demonstrated. The relationships between the signal’s DOP and coding length/bit width were studied. Both numerical simulations and experiments show that the signal’s DOP has nothing to do with the length of Simplex code and only reducing the bit width can suppress the temporal depolarization effect. Applying 511-bit Simplex codes, a coding gain of 10.125dB has been demonstrated.
Slope-assisted BOTDR for pipeline vibration measurements
Author(s):
Damien Maraval;
Renaud Gabet;
Yves Jaouën;
Vincent Lamour
Show Abstract
Brillouin distributed optical fiber strain sensors are often limited to static events because of the long acquisition time due to the classic frequency sweep technique. Recently, BOTDA sensor based on slope-assisted (SA) method has been proposed for fast strain measurement along the sensing fiber. In this paper, we present a novel dynamic SA-BOTDR for single-ended truly distributed strain measurement. Geometrical displacement and damping time of a 10.4 m instrumented pipe with a 3 glued fibers system. A 7.6 Hz acquisition rate was achieved with a strain error of 40 με and a 1m spatial resolution. From integration of longitudinal strains, local pipe displacement is calculated with a 12 mm precision.
Distributed photothermal measurements of gas presence along holey optical fibers
Author(s):
Andres Garcia-Ruiz;
Juan Pastor-Graells;
Hugo F. Martins;
Kenny Hey Tow;
Luc Thévenaz;
Sonia Martin-Lopez;
Miguel Gonzalez-Herraez
Show Abstract
Chirped-pulse phase-sensitive optical time domain reflectometry has shown a remarkable performance when applied to dynamic measurements of strain and temperature, recently reaching ranges of several kilometers while interrogating the fiber at acoustic frequencies. In this work, its sensitivity, fast response, and high spatial resolution are exploited to implement a proof-of-concept of a selective distributed chemical sensor based on the photothermal effect. The presented scheme is able to perform distributed spectroscopic measurements of acetylene presence along a 10 m-long holey fiber. This potentially gives rise to a new kind of distributed chemical sensors capable of tracking the concentration of chemical species over kilometres.
Tunable liquid crystal fibre optic filter
Author(s):
Joanna E. Mos;
Mariusz Florek;
Katarzyna Garbat;
Karol A. Stasiewicz;
Noureddine Bennis;
Leszek R. Jaroszewicz
Show Abstract
The present work has been centered in the design, fabrication and characterization of a new in-line tunable nematic liquid crystal (TNLC) optical fiber device. The main reason of using a biconical optical fibre taper as a core surrounded by liquid crystals molecules is the possibility to change the losses by the electrically induced reorientation of liquid crystal molecules. A taper is made from a standard fiber SMF28®, whereas the clad uses the nematic mixture 1550C1 type. A supercontinuum source with a bandwidth of [500-700 nm] and laser with wavelength 532 nm were used as light sources.
High density distributed strain sensing of landslide in large scale physical model
Author(s):
L. Schenato;
M. Camporese;
S. Bersan;
S. Cola;
A. Galtarossa;
A. Pasuto;
P. Simonini;
P. Salandin;
L. Palmieri
Show Abstract
This paper describes the application of a commercial distributed optical fiber sensing system to a large scale physical model of landslide. An optical fiber cable, deployed inside the landslide body, is interrogated by means of optical frequency domain reflectometry with very high spatial density. A shallow landslide is triggered in the physical model by artificial rainfall and the evolution of the strain is measured up to the slope failure. Precursory signs of failure are detected well before the collapse, providing insights to the failure dynamic.
Performance improvement of BOTDR system using wavelength diversity technique
Author(s):
Nageswara Lalam;
Wai Pang Ng;
Xuewu Dai;
Qiang Wu;
Yong Qing Fu
Show Abstract
In this paper, a novel technique was proposed to improve the sensing performance by employing wavelength diversity in Brillouin optical time domain reflectometry (BOTDR). This technique enables to maximize the launch pump power to achieve a higher measurement accuracy, without activating the nonlinear effects, which limit the conventional BOTDR performance. Experimentally, we have demonstrated the proposed technique, that provides measurement accuracy improvement of 3.6 times at far end of the sensing fibre compared to the conventional BOTDR system.
Multiwavelength erbium-doped fiber laser based on an all-fiber polarization interference filter
Author(s):
Hushan Wang;
Zhijun Yan;
Kaiming Zhou;
Jiazheng Song;
Ye Feng;
Yishan Wang
Show Abstract
We demonstrated a compact stable room-temperature multiwavelength erbium doped fiber laser by employing a 45° tilted fiber gratings (TFGs) based all-fiber polarization interference filter. Benefiting from the filter, the channel number, the linewidth, the uniformity and stabilization of the multiwavelength laser were greatly improved. The filter also worked as a polarizing functional device in nonlinear polarization rotation leading to multiwavelength operation. More than 60 wavelengths (within 3dB bandwidth) lasing with a linewidth of 0.03nm and a signal-to-noise ratio of 31dB were obtained. The wavelength spacing was 0.164nm agreeing with the value of the filter and it can be flexibly controlled by adjusting the length of the filter.
An optical fiber MEMS pressure sensor using microwave photonics filtering technique
Author(s):
Yiping Wang;
Ming Wang;
Xiaoqi Ni;
Wei Xia;
Dongmei Guo;
Hui Hao;
Qingyu Ma;
Wei Zhuang
Show Abstract
A fiber-optic micro-electromechanical systems (MEMS) extrinsic Fabry-Perot interferometer (EFPI) pressure sensor exploiting microwave photonics filtering technique is firstly proposed and experimentally demonstrated. A single-bandpass microwave photonic filter (MPF) which mainly consists of a spectrum-sliced light source, a pressurized EFPI, a phase modulator (PM) and a length of dispersion compensating fiber (DCF) is demonstrated. The frequency response of the filter with respect to the pressure is studied. By detecting the resonance frequency shifts of the MPF, the pressure can be determined. The theoretical and experimental results show that the proposed EFPI pressure sensor has a higher resolution and higher speed than traditional methods based on optical spectrum analysis. The sensitivity of the sensor is measured to be as high as 86 MHz/MPa in the range of 0-4MPa.
BOCDA system enhanced by concurrent interrogation of multiple correlation peaks with a 10-km sensing range
Author(s):
Gukbeen Ryu;
Gyu-Tae Kim;
Kwang Yong Song;
Sang Bae Lee;
Kwanil Lee
Show Abstract
A Brillouin optical correlation domain analysis (BOCDA) system using time-domain data processing for concurrently interrogating a plurality of sensing positions is proposed, where the time-domain data processing combined with differential measurement effectively enhances the measurement range and measurement time as much as the spatial resolution of the BOCDA system. In the experiment, the distribution of the Brillouin gain spectra (BGS) along a 10.15 km test fiber is successfully obtained with a spatial resolution less than 5 cm by concurrently interrogating 980 correlation peaks.
Skew rays analysis to determine radial position of defects within optical fibers
Author(s):
George Y. Chen;
Tanya M. Monro;
David G. Lancaster
Show Abstract
Defects in optical fibers can cause severe damage, and thus must be found and repaired/replaced early. Such defects in fibers and their coatings can be detected using an angle-resolved interrogator that exploits the contribution of different ray groups. This approach can also estimate the radial position of defects within the fiber. A demonstration is performed with a femtosecond-laser-induced internal defect inside the cladding.
Study of gamma-ray radiation effects on TW-COTDR optical fiber sensors
Author(s):
I. Planes;
S. Girard;
A. Boukenter;
E. Marin;
S. Delepine-Lesoille;
A. Gusarov;
Y. Ouerdane
Show Abstract
Radiation effects on the performances of TW-COTDR (Tunable Wavelength - Coherent Optical Time Domain Reflectometry) optical fiber sensors based on Rayleigh scattering have been studied online for Ge-doped and F-doped fibers. We confirm that the Rayleigh response is not affected by low radiation (dose ∼55 kGy). However we observed using the TW-COTDR technology, a radiation induced frequency shift increasing at higher radiation (dose ∼ 10MGy): up to 96 GHz for Ge-doped fiber and up to 25.5 GHz for F-doped fiber.
Fibre optic gyroscope as instrumental challenge for rotational seismology
Author(s):
Anna Kurzych;
Leszek R. Jaroszewicz;
Zbigniew Krajewski;
Bartosz Sakowicz;
Jerzy K. Kowalski;
Paweł Marć
Show Abstract
Rotational Seismology caused highly interest in investigation of rotational movements generated by earthquake, mines and existing in engineering structures. The most oppressive aspect of research in this field is technical requirements for sensors. However, the instruments basing on the Sagnac effect seem to be the most appropriate to investigate rotational effects due to the fact that they are entirely insensitive to translational motion and are able to measure rotation rate in wide frequency and amplitude band. The paper presents a new device FOSREM which, based on FOG, possesses special solutions that makes it perfect, in author knowledge, for any rotation sensing.
Few mode fibers based quasi-single mode Raman distributed temperature sensor
Author(s):
Hao Wu;
Meng Wang;
Tongqing Liu;
Chen Yang;
Weijun Tong;
Songnian Fu;
Ming Tang
Show Abstract
We demonstrate a distributed temperature sensor based on quasi-single mode (QSM) Raman scattering in few mode fibers (FMFs). The FMF allows much larger input pump power before the initiate of stimulated Raman scattering compared with the standard single mode fiber (SSMF) and mitigates the detrimental differential mode group delay (DMGD) existing in the conventional multimode fiber (MMF) based Raman distributed temperature sensor (RDTS). Distributed temperature sensing is realized using conventional RDTS hardware over 20km FMFs within 90s, with a spatial resolution of 3m. The temperature resolution is 2.3°C @10km and 6.7°C @20km, respectively.
Sweep free BOTDA based on DD-OOFDM channel estimation
Author(s):
Can Zhao;
Jiadi Wu;
Hao Wu;
Zhiyong Zhao;
Yunli Dang;
Songnian Fu;
Ming Tang
Show Abstract
A novel Brillouin optical time-domain analysis (BOTDA) system is demonstrated using intensity-modulated optical orthogonal frequency division multiplexing probe signal and direct detection (IM-DD-OOFDM) for stimulated Brillouin spectrum (SBS) measurement without frequency sweep operation. The SBS is reconstructed by channel estimation algorithm and Brillouin frequency shift (BFS) is located by curve fitting. The IM-DD-OOFDM BOTDA is demonstrated experimentally with 25m spatial resolution over 2 km standard single mode fiber.
Safe and private pedestrian detection by a low-cost fiber optic specklegram
Author(s):
A. Rodriguez-Cuevas;
L. Rodriguez-Cobo;
M. Lomer;
J. M. Lopez-Higuera
Show Abstract
Surveillance is becoming more and more important in the recent years. In many cities, cameras have been set to look after parks, streets, roads, facilities and so on, however this fact is rising concerns about privacy. In this work, an alternative surveillance method which gather at once security and privacy has been propose and tested. Based on fiber optic specklegram technology; a system consisting of a fiber optic, a coherent light source and a photodetector has been placed under a carpet for detecting people walking over it and its accuracy, regarding measuring the steps, have been measured. Results suggest that using low exposed geometries along the carpet and basic processing methods, it is possible to detect with more than 95% of accuracy the number of steps done by the person walking over the carpet.
Compared performances of Rayleigh, Raman, and Brillouin distributed temperature measurements during concrete container fire test
Author(s):
S. Delepine-Lesoille;
I. Planes;
M. Landolt;
G. Hermand;
O. Perrochon
Show Abstract
We present a distributed fiber optic sensing scheme to study 3D temperature fields inside concrete containers submitted to fire. High spatial resolution (3cm to 13cm), temperature uncertainty better than 3°C and rapid measurements (in the minute range) were required. We thus compared advantages and drawbacks of three sensing chains, based on Rayleigh, Brillouin and Raman scatterings; such distributed measurements were also compared with thermocouples (up to 250 measuring points). Practical field implementation limits are also underlined. Fire tests are a promising application for distributed optical fiber sensors.
Model-based compressed sensing of fiber Bragg grating arrays in the frequency domain
Author(s):
Stefan Werzinger;
Michael Gottinger;
Sandra Gussner;
Sven Bergdolt;
Rainer Engelbrecht;
Bernhard Schmauss
Show Abstract
We propose a model-based compressed sensing (MBCS) of FBG arrays (FBGA), interrogated with wavelength scanning incoherent optical frequency domain reflectometry. This method measures the frequency response of a FBGA with an electrical vector network analyzer combined with a tunable laser. Instead of the usual inverse discrete Fourier transform (IDFT), we apply a direct estimation of the grating reflectivities with a simple frequency domain model. A reconstruction of 10 gratings spaced by 20 cm is demonstrated. MBCS allows to reduce the number of measurement frequencies from 120 to 8, compared to an IDFT, while using a bandwidth of just 500 MHz.
Performance characteristics of continuously grated multicore sensor fiber
Author(s):
Paul S. Westbrook;
Tristan Kremp;
Kenneth S. Feder;
Wing Ko;
Eric M. Monberg;
Hongchao Wu;
Debra A. Simoff;
Scott Shenk;
Roy M. Ortiz
Show Abstract
We describe the fabrication and performance of a continuously grated twisted multicore fiber sensor array. The grated fiber sensor comprises nearly continuous Bragg gratings along its entire length. The gratings are inscribed over lengths in excess of 10m in fibers with UV transparent coating using a flexible and scalable reel to reel processing system. The arrays are tested using optical frequency domain reflectometry (OFDR). We report on automated analysis routines applied to these OFDR measurements that allow for characterization of 100s of individual grating exposures that make up a continuously grated fiber length. We also report on the spectral loss of the continuously grated fiber, showing that it is suitable for applications with sensors in excess of 100m. Finally, we report on the fiber sensing characteristics by performing measurements of fiber bend using a fiber shape reconstruction algorithm on OFDR traces obtained from four of the fiber cores.
Application of bridge continuous shape measurement system based on optical fiber sensing technology in bridge post-seismic detection
Author(s):
Yan Yang;
Fang Liu;
Jinghua Fu;
Dandan Yang
Show Abstract
Bridge shape is the important indicator to estimate the safety of the bridge. A bridge shape measurement system based on fiber optic gyroscope is builded up to survey the continuous shape of bridge. This measurement system comprises angular velocity sensor, linear velocity sensor, position sensor and etc. The bridge shape survey using the leveling measurement and bridge continuous shape measurement system was carried out after the earthquake. By comparing the data before and after the earthquake, the numerical values of the two method were similar. The experimental results show that the proposed system is an effective measurement method.
High-speed identical weak fiber Bragg grating interrogation system using DFB laser
Author(s):
Chun Zhang;
Siqi Liu;
Yiming Wang;
Jiapei Liu;
Honghai Wang;
Zhengying Li
Show Abstract
A high-speed fiber Bragg grating (FBG) interrogation system is realized by using the high-speed sweep characteristic of Distributed feedback (DFB) laser to constitute a high-speed wavelength-swept laser. To solve the problem of narrow scanning width of the DFB laser and low reuse capacity of the system, the method of building a time division multiplexing (TDM) sensor network with identical weak fiber Bragg grating is proposed. By using the transmission delay of light between the gratings to separate the grating reflection spectrum in time-domain and demodulating the reflection scanning spectrum of each grating to realize the wavelength demodulation. Experimental results show that, under a constant interrogation frequency on 100kHz of the system, 10 identical weak FBGs with the center wavelength of 1553.7nm and reflectivity of 1％ have achieved demodulation in a single fiber. And within the temperature range from 25°C to 79°C the linearity of each FBG’s center wavelength varying with the temperature reaches 0.99 .
Resonant wavelength thermal stability of femtosecond FBGs
Author(s):
Tiago Paixão;
Francisco Araújo;
Luís Ferreira;
Paulo Antunes
Show Abstract
We report on a thermal stability study of the resonant wavelength of fiber Bragg gratings fabricated by femtosecond laser. We propose a new method to analyze the decay of the central wavelength shift of Bragg gratings based on isothermal and isochronal processes up-to a maximum temperature of 800°C. The obtained thermal decay follows a typical power-law function, which allowed us to fit theoretical equations to our experimental data and simulate the refractive index decay. A method to mitigate this decay is proposed and the results demonstrate the potential of using femtosecond fiber Bragg gratings as high temperature sensors.
Fiber Bragg grating-based detection of cross sectional irregularities in metallic pipes
Author(s):
Pabitro Ray;
Balaji Srinivasan;
Krishnan Balasubramaniam;
Prabhu Rajagopal
Show Abstract
Cross-sectional irregularities such as eccentricity are an important problem for pipe and tubing infrastructure. Recent work by the authors shows that such axially extended pipe irregularities can cause confinement and feature-guiding of lower order ultrasonic guided waves. In this paper, we demonstrate a technique to monitor such irregularities in pipes by detecting the feature-guided waves using fiber Bragg grating sensors. Our experimental results are in good agreement with the results reported in elastic wave literature.
Magnetic field measurement by using a multilongitudinal mode fiber laser
Author(s):
Ming Deng;
Danhui Liu;
Yong Zhao;
Tao Zhu
Show Abstract
In this paper, a magnetic field sensor based on a multilongitudinal mode fiber laser has been proposed by employing a rotary apparatus modulated by an external magnetic field. Due to the remarkable birefringence change caused by the fiber twist, the polarimetric mode beat frequency (PMBF) of the laser is sensitive to the applied magnetic field intensity. Experimental results show that the PMBF linearly shifts with the variation of the magnetic field intensity and the sensitivity reaches up to 10.4 KHz/Oe in the range of 0 - 270Oe.
Transient Brillouin optical correlation domain analysis
Author(s):
Eyal Preter;
Dexin Ba;
Orel Shlomi;
Yosef London;
Avi Zadok
Show Abstract
High spatial resolution measurement of the Brillouin frequency shift (BFS) is accomplished using transient analysis. The step response of the output signal wave is recorded for an arbitrary, known frequency offset between pump and signal, and compared against a library of modeled, reference functions. No spectral scanning or prior knowledge of the BFS is necessary. The principle is employed in a Brillouin optical correlation domain analysis (B-OCDA) of a 4 cm-wide fiber segment. A dynamic range of 130 MHz and an accuracy of ±1.9 MHz are achieved. Transient analysis may improve the precision and acquisition rate of B-OCDA.
Impact of the probe pulse shape on the performance of phase-sensitive optical time-domain reflectometry sensors
Author(s):
María R. Fernández-Ruiz;
Hugo F. Martins;
Juan Pastor-Graells;
Sonia Martin-Lopez;
Miguel Gonzalez-Herraez
Show Abstract
In this communication, the effect of the probe pulse shape on the backscattered power trace of phase-sensitive (φ-) OTDR is analyzed. In particular, the power traces obtained with rectangular and Gaussian-like probe pulses are compared, both numerically and experimentally. Our analysis reveals that the use of Gaussian-like pulses can increase the operation range and sensitivity of φOTDR-based sensors in at least two-fold as compared with that obtained from traditionally-employed rectangular-like pulses.
A liquid level sensing system based on high attenuation fiber and DPP-BOTDA
Author(s):
Hongying Zhang;
Ziye Liu;
Zhijun Yuan;
Wei Gao;
Yongkang Dong
Show Abstract
A novel liquid-level sensing system based on differential pulse-width pair Brillouin optical time domain analysis technology with a self-heated high attenuation fiber (HAF) is proposed and demonstrated in this paper, where the principle is to measure the temperature abruption position at the interface between liquid and air caused by the different thermal diffusion rates of the two kinds of mediums. The sensing optical fiber was glued to a 1-m HAF with an absorption coefficient of 20 dB/m, so that heat can be transmitted from the HAF to the sensing fiber through physical contact, which will cause temperature increase of the latter. The Brillouin frequency shift (BFS) profiles of the sensing fiber when the HAF was heated by different heating optical powers were characterized to find out the optimized heating power. The BFS distributions were measured for different water levels, with the result indicating that liquid-level sensing with a range of 20 cm and a resolution of 1 cm is realized.
Laser Brazing metallic embedding technique for fiber optic sensors
Author(s):
Tania Grandal;
Sergio Fraga;
Gemma Castro;
Esteban Vazquez;
Ander Zornoza
Show Abstract
In this paper a fiber optic metallic embedding technique is presented based on laser Brazing manufacturing process. The embedding strategy to follow by the laser Brazing, which consists in three steps, minimizes the thermal stress of the embedded fiber, relaxes microbending strains and reduces damage on the fiber. The minimum embedded fiber optic Ni coating total diameter is 237 μm for a successful process with negligible optical loss on the fiber. Fiber Bragg Gratings were successfully embedded in metallic specimens and their strain response was in accordance with their specifications.
A temperature compensated fibre Bragg grating (FBG)-based sensor system for condition monitoring of electrified railway pantograph
Author(s):
Ye Chen;
Miodrag Vidakovic;
Matthias Fabian;
Martin Swift;
Lee Brun;
Tong Sun;
Kenneth T. V. Grattan
Show Abstract
This paper presents the results obtained from fibre Bragg grating (FBG) sensors integrated into a railway current-collecting pantograph for accurate measurement of contact force and contact location when it is subjected to various temperature conditions. The temperature change of the pantograph is simulated, at the industrial laboratory of Brecknell Willis in the UK, by changing the DC current applied to pantograph from 0 to 1500 A. This test is primarily designed to verify the effectiveness of the temperature compensation mechanism built in the FBG sensor design. For this verification, 3 thermocouples co-located with the FBG sensor packages are used to measure the temperature change seen from 25 °C to 55 °C. The tests were repeated several times and the sensor system has shown its temperatureindependence, confirming that the intrinsic cross-sensitivity of FBGs to temperature variation for strain measurement has been fully compensated through the use of this innovative sensor design and data processing.
Numerical study on refractive index sensor based on hybrid-plasmonic mode
Author(s):
Jeong-Geun Yun;
Joonsoo Kim;
Kyookeun Lee;
Yohan Lee;
Byoungho Lee
Show Abstract
We propose a highly sensitive hybrid-plasmonic sensor based on thin-gold nanoslit arrays. The transmission characteristics of gold nanoslit arrays are analyzed as changing the thickness of gold layer. The surface plasmon polariton mode excited on the sensing medium, which is sensitive to refractive index change of the sensing medium, is strengthened by reducing the thickness of the gold layer. A design rule is suggested that steeper dispersion curve of the surface plasmon polariton mode leads to higher sensitivity. For the dispersion engineering, hybrid-plasmonic structure, which consists of thin-gold nanoslit arrays, sensing region and high refractive index dielectric space is introduced. The proposed sensor structure with period of 700 nm shows the improved sensitivity up to 1080 nm/RIU (refractive index unit), and the surface sensitivity is extremely enhanced.
An in-fiber Mach-Zehnder interferometer based on dual side-hole fiber for highly sensitive measurement of curvature
Author(s):
Xiaowei Ouyang;
Huiyong Guo;
Zhou Zheng;
Liyun Ding;
Ai Zhou
Show Abstract
An in-fiber Mach-Zehnder interferometer (MZI) based on dual side-hole fiber (DSHF) was demonstrated for highly sensitive measurement of curvature. The MZI-based bending sensor is fabricated by fusion splicing a piece of DSHF in between two standard single mode fibers (SMF) with cladding alignment. Due to the existence of the two air holes and the asymmetrical cross-section of the DSHF, the DSHF-based MZI is a core-cladding interferometer which is sensitive to directional bending. The bending characteristics are investigated experimentally within the curvature range of 0-8.172m-1. The bending sensitivities of the sensor are respectively 1.464 nm/m-1 and -1.394 nm/m-1 at their two opposite bending directions.
Dual-mode optofluidic flow rate sensor
Author(s):
Yuan Gong;
Liming Qiu;
Chenlin Zhang;
Yu Wu;
Yun-Jiang Rao;
Gang-Ding Peng
Show Abstract
A dual-mode optofluidic flow rate sensor with a large dynamic range of 4 orders of magnitude is developed. The sensing mechanism is based on the force balance on an optically trapped polystyrene microparticle. As the optical force is very small, the flow rate sensor is very sensitive. In the open-loop mode, the manipulation length is used as the sensing signal. The sensor has an inverse sensitivity, that is, the manipulation length decreases as the flow rate increases, so that it has high sensitivity at low flow rate. In the closed-loop mode, the manipulation length is set to be constant and a feedback signal to tune the laser power for force balance is used as the sensing signal. The closed-loop mode is helpful for extending the upper limit of flow rate and also enhancing the sensitivity at high flow rate.
Monitoring on internal temperature of composite insulator with embedding fiber Bragg grating for early diagnosis
Author(s):
Wen Chen;
Ming Tang
Show Abstract
The abnormal temperature rise is the precursor of the defective composite insulator in power transmission line. However no consolidated techniques or methodologies can on line monitor its internal temperature now. Thus a new method using embedding fiber Bragg grating (FBG) in fiber reinforced polymer (FRP) rod is adopted to monitor its internal temperature. To correctly demodulate the internal temperature of FRP rod from the Bragg wavelength shift of FBG, the conversion coefficient between them is deduced theoretically based on comprehensive investigation on the thermal stresses of the metal-composite joint, as well as its material and structural properties. Theoretical model shows that the conversion coefficients of FBG embedded in different positions will be different because of non-uniform thermal stress distribution, which is verified by an experiment. This work lays the theoretical foundation of monitoring the internal temperature of composite insulator with embedding FBG, which is of great importance to its health structural monitoring, especially early diagnosis.
Guided acoustic waves Brillouin scattering in multi-core fibers
Author(s):
H. Hagai Diamandi;
Yosef London;
Avi Zadok
Show Abstract
Guided acoustic waves Brillouin scattering (GAWBS) was recently shown to facilitate chemical sensing outside the cladding of an unmodified fiber, even though the guided light wave never reaches the substance under test. In this work, the study of GAWBS is extended to commercially-available, multi-core fibers. We show that GAWBS leads to inter-core cross-phase modulation, between cores that are otherwise optically isolated from one another. The observed modulation spectrum is in excellent agreement with the predictions of an opto-mechanical analysis of the fiber. Use of multi-core fibers would improve the signal-to-noise ratio in GAWBS-based sensors, and may enable distributed analysis.
Combined Sagnac and intermodal interferences for discrimination of strain and temperature variations
Author(s):
Guoyong Sun;
Yingxin Cen;
Liyan Zhao;
Chuliang Wei;
Youngjoo Chung
Show Abstract
A fiber sensor capable of discriminating the strain and temperature variations is presented and fully investigated. Its simple configuration is a Sagnac interferometer containing only one piece of high birefringence few-mode fiber and a polarization controller in the loop arm. The Sagnac and intermodal interferences are generated simultaneously. Based on the combined interferences, it is possible to decouple the strain and temperature changes by monitoring the wavelength and power of one localized peak originating from the intermodal interference in the spectral response of the Sagnac interferometer.
Mechanical strain-amplifying transducer for fiber Bragg grating sensors with applications in structural health monitoring
Author(s):
Urszula Nawrot;
Thomas Geernaert;
Ben De Pauw;
Dimitrios Anastasopoulos;
Edwin Reynders;
Guido De Roeck;
Francis Berghmans
Show Abstract
A well-known structural health monitoring method used to detect and locate damage in civil engineering structures is vibration-based damage identification. It typically monitors the civil structure over time to spot slow or sudden changes in its natural frequencies, damping factors or modal displacements. This approach can prove very powerful, but the sensitivity of those properties to local damage can be rather low. In addition, their cross-sensitivity to environmental influences may completely mask the effect of damage, even of severe damage. Instead one can consider the modal strains and curvatures, which are much more sensitive to local damage, but direct (quasi-)distributed monitoring of these quantities with sufficient strain resolution as well as adequate spatial resolution is not straightforward with current measurement techniques. This stems from the small (sub-microstrain) amplitudes of the strain levels occurring following ambient or operational excitation of the structure under test. To deal with this issue we propose and demonstrate a novel mechanical transducer that amplifies the strain applied to an optical fiber Bragg grating sensor with a factor of about 36. In addition the transducer resonance frequencies are sufficiently high to ensure accurate dynamic strain monitoring of civil structures under ambient excitation.
Temperature sensitivity enhancement in a standard optical fiber with double coatings at low temperature
Author(s):
Xin Lu;
Marcelo A. Soto;
Luc Thévenaz
Show Abstract
The thermomechanical behavior of a standard optical fiber with double coating is theoretically analyzed at room temperature and ∼ 220 K. As the primary coating becomes stiffer at low temperature, the impact of the thermal expansion of the coatings is no longer negligible and contributes to the thermal response of the fiber sensor. The temperature sensitivity enhancement is validated by distributed fiber sensors based on Brillouin scattering and coherent Rayleigh scattering at 220 K; the experimental results agree well with the theoretical analysis.
High sensitivity curvature sensor with a cascaded fiber interferometer
Author(s):
Shandong Dong;
Bo Dong;
Changyuan Yu
Show Abstract
This paper presents a cascaded fiber interferometer sensor, which is fabricated by fusion splicing of single-mode fibers. The coupling and interference for the CFI were mathematically and experimentally studied. An equal model has been built for the CFI. Furthermore, the curvature sensitivity were explored in sensor application. The curvature sensitivity for the cascaded fiber interferometer is very high, which can achieve 790.18 pm/m−1. Besides, the proposed sensor has advantages like good repeatability, low cost, and simple structure.
Low cost portable sensor for real-time monitoring of lower back bending
Author(s):
Wern Kam;
Kieran O'Sullivan;
Waleed S. Mohammed;
Elfed Lewis
Show Abstract
A mechanically robust and compact optical fibre sensor system is described to monitor the bending of the lower back bone in both sagittal and frontal plane. Both bending modes are monitored through the change of the coupled optical intensity ratio between three output fibers aligned to one input fiber. This provides real time feedback when different postures are sustained. The output ratio is calibrated to bending angles using an optical setup that utilized a precise rotational stage. An operation range between -12° to 12° is demonstrated. It is also demonstrated that sensor is suitable for use in a clinical diagnosis system with the additional benefits of being non-invasive, robust, straightforward to use and low cost.
A novel fiber Michelson interferometer based on cascaded twin core fiber and side-hole fiber
Author(s):
Yujia Zhao;
Huiyong Guo;
Zhou Zheng;
Lina Yue;
Yimin Xu;
Ai Zhou;
Libo Yuan
Show Abstract
We present and demonstrate a novel fiber Michelson interferometer based on cascaded twin core fiber (TCF) and side-hole fiber (SHF) for curvature measurement. The interferometer is fabricated by fusing the TCF and SHF. The interferometer can measure curvature and temperature by monitoring the wavelength change of interferometer spectrum. The experiment investigated sensor’s spectral responses to the curvature at different bending directions. Experimental results show that the bending sensitivities of the sensor are -6.968 nm/m-1 and 6.978 nm/m-1 at the bending direction of 0° and 180°, respectively. The temperature sensitivity of the interferometer is 10.37pm/°C.
Simultaneous measurement of temperature and bend by using an eccentric core fiber Bragg grating cascaded with a Fabry-Perot cavity
Author(s):
Yang Ouyang;
Jing Kong;
Yimin Xu;
Ai Zhou;
Libo Yuan
Show Abstract
A simultaneous temperature and bend sensor based on an eccentric core fiber Bragg grating (ECFBG) cascaded with a Fabry-Perot cavity is presented and demonstrated. The hybrid structure is composed of a piece of hollow core fiber, which is sandwiched in between a piece of multimode fiber and an ECFBG. The curvature sensitivities of the ECFBG at the two opposite most sensitive directions are 52.2 pm/m-1 and -51.7 pm/m-1 respectively, and those of the FPI are 58.6pm/m-1 and -61.4 pm/m-1, respectively. The temperature sensitivities of the two parts are very different. The temperature sensitivity of the ECFBG is 10.3 pm/°c, and that of the FPI is as low as 0.7 pm/°c.
Textile carbon reinforcement structures with integrated optical fibre sensors designed for SHM applications
Author(s):
L. S. M. Alwis;
K. Bremer;
F. Weigand;
M. Kuhne;
R. Helbig;
B. Roth
Show Abstract
An optical fibre-based strain sensor embroidered to a functionalised carbon structure (FCS) that can be used for structural health monitoring (SHM) is introduced. The aim of the design is not only to monitor strain, but also to act as a structural strengthening mechanism in the target application. The integration of optical fibres on the FCS is achieved by “interweaving” the two elements on a polymer textile substrate in a grid formation using a specialised fabrication process. The thus obtained sensor was then characterised using a fibre optic Mach-Zehnder (MZ) interferometric setup where a variation in the fibre length, i.e. resulting from strain, would induce a variation in the interference pattern. To do so, two different functionalised skein samples (incorporating optical fibres) were subjected to varying elongation using a tensile testing machine by carefully incrementing the applied force. A good correlation between the applied force and measured length change was observed, showing the value of the dual-achievement of the proposed optical fibre-based mechanism in obtaining strain measurement while being utilised as a strengthening agent.
Asymmetrical twin-core fiber based Michelson interferometer for environmental refractive index sensing
Author(s):
Shaoxian Zhang;
Tingting Yuan;
Libo Yuan
Show Abstract
We presented a type of refractive index sensor based on Michelson interferometer by using asymmetrical twin-core fiber. The central-core and side-core of the asymmetrical twin-core fiber are used as the reference arm and sensor arm respectively, and the D-shape side-polish sensing region are fabricated on the sensing arm by the side-polishing technique. The optical path difference is formed between the two arms due to the sensing region of the side-core sensitive to the change of the surrounding refractive index. Thus, through the reflection of the end and taper of the fiber to achieve the interference of transmission to form Michelson interferometer. Therefore, the changes of the surrounding will lead to the shift of the transmission spectrum to reach the purpose of the sensing. The experimental results show that the device has a maximum refractive index sensitivity of about -80nm/RIU in the range of 1.333-1.3824 and the result is basically consistent with the simulation. This sensor is a simple structure and convenient in its production advantages, and can be used in many areas such as biological sensing and chemical sensing.
Simultaneous strain and directional bending sensor based on eccentric-core fiber Bragg grating
Author(s):
Jing Kong;
Xiaowei Ouyang;
Ai Zhou;
Libo Yuan
Show Abstract
A fiber sensor based on cascaded eccentric-core fiber Bragg grating (ECFBG) and single mode fiber Bragg grating (SMFBG) is proposed and experimentally demonstrated to realize bending and axial strain measurement simultaneously. The ECFBG is sensitive to both bending and axial strain, and the SMFBG is insensitive to bend but sensitive to axial strain. The maximum bending sensitivities of the ECFBG are 36 pm/m-1 and -37 pm/m-1 at the bending direction of 0° and 180°, respectively. The strain sensitivities of the ECFBG and SMFBG are 0.76 pm/με and 0.72 pm/με, respectively.
Memristor-capacitor passive filters to tune both cut-off frequency and bandwidth
Author(s):
Shawkat Ali;
Arshad Hassan;
Gul Hassan;
Jinho Bae;
Chong Hyun Lee
Show Abstract
In various optical sensor applications, programmable analog filters are desirable to reduce the hardware requirement. Memristor is two state programmable nonvolatile resistor, which has a small size and low power consumption. Using these resistance switching characteristics of a memristor, we propose a novel memristor-capacitor (MC) based printed low pass and high pass filters for analog circuits to achieve tunable cut-off frequencies and bandwidth. The cut-off frequencies of filters are controlled through a memristor state switching (HRS/LRS), whereas the capacitor has a fixed value. The proposed MC filters utilize graphene/poly 4-vinlyphenol (G/PVP) for dielectric layer of capacitors and Graphene Quatum Dots (GQDs)/PVP for an active layer of memristor, and these layers are fabricated on ITO coated flexible PET substrate through electrohydrodynamic (EHD) technique. Both MC filters are designed as parameters of two state memristance and a capacitance. From comparison between designed and fabricated filters, we show that they are matched quite well.
Effective mode-field diameter measurement for few-mode fibers
Author(s):
Takashi Matsui;
Taiji Sakamoto;
Kazuhide Nakajima
Show Abstract
We experimentally investigate the applicability of the conventional near-field patter (NFP), far-field pattern (FFP) and variable aperture (VA) methods for measuring the effective mode-field diameter (MFD) of the higher-order mode which can be used for evaluating the splice loss accurately. We confirmed that the variation in measured MFD values obtained with FFP and VA methods can be converged by considering the minimum scanning angle and minimum numerical aperture (NA) respectively for both fundamental and higher-order modes. We reveal that the FFP and VA methods provide adequate effective MFD values in the FMF, which can be used for evaluating the splice loss based on the traditional Gaussian fitting model. We also found that the minimum NA in the VA method can be determined empirically as a function of the effective MFD.
A comparison of clinic based dosimeters based on silica optical fibre and plastic optical fibre for in vivo dosimetry
Author(s):
Lingxia Chen;
Sinead O'Keeffe;
Peter Woulfe;
Elfed Lewis
Show Abstract
Four sensors based on silica optical fibre and plastic optical fibre for clinical in-vivo dosimetry have been fabricated and tested on site at Galway Clinic. The initial comparison results have been attained for the four sensors when they have been irradiated with beam energies of 6 MV and 15 MV at different dose rates using a modern clinical linear accelerator (Linac) as the radiation source. According to the experimental test results, the sensors based on silica optical fibre exhibit greater sensitivity to the incident radiation beam than the sensors based on plastic optical fibre when they are exposed to identical irradiation conditions. The output intensity from the sensor based on silica fibre is 5 times higher than the sensor based on plastic optical fibre.
Enhancement of signal-to-noise ratio in Brillouin optical time domain analyzers by dual-probe detection
Author(s):
Haritz Iribas;
Alayn Loayssa;
Florian Sauser;
Miguel Llera;
Sébastien Le Floch
Show Abstract
We demonstrate a simple technique to enhance the signal-to-noise ratio (SNR) in Brillouin optical time-domain analysis sensors by the addition of gain and loss processes. The technique is based on the shift of the pump pulse optical frequency in a double-sideband probe system, so that the gain and loss processes take place at different frequencies. In this manner, the loss and the gain do not cancel each other out, and it makes possible to take advantage of both informations at the same time, obtaining an improvement of 3 dB on the SNR. Furthermore, the technique does not need an optical filtering, so that larger improvement on SNR and a simplification of the setup are obtained. The method is experimentally demonstrated in a 101 km fiber spool, obtaining a measurement uncertainty of 2.6 MHz (2σ) at the worst-contrast position for 2 m spatial resolution. This leads, to the best of our knowledge, to the highest figure-of-merit in a BOTDA without using coding or raman amplification.
Second-order non-local effects mitigation in BOTDA sensors by tracking the BFS profile
Author(s):
Juan José Mompó;
Haritz Iribas;
Javier Urricelqui;
Alayn Loayssa
Show Abstract
We demonstrate a technique to mitigate the residual second-order non-local effects in Brillouin optical time-domain analysis (BOTDA) sensors in which the Brillouin frequency shift (BFS) profile is not uniform along the fiber. It is based on adding a wavelength modulation to the probe wave that makes it track the average BFS found along its way. Using this method we are able to inject a total probe wave power of 15 dBm in a 120-km sensing fiber link, which, to the best of our knowledge, is the highest probe power ever demonstrated in a long-range BOTDA sensing fiber link. The enhancement in the detected signal-to-noise ratio brought by the use of such power provides 2-MHz BFS measurement precision at the end of the 120-km sensing link with 3-m spatial resolution, all without the need to resort to additional means such as the use of coding or Raman gain.
Simultaneous strain and temperature measurements using dual-wavelength BOTDA
Author(s):
E. Catalano;
R. Laiso;
R. Bernini;
L. Zeni;
A. Minardo
Show Abstract
Brillouin scattering properties of a bend-insensitive fiber were experimentally investigated at 850 nm and 1550 nm wavelength using Brillouin optical time-domain analysis (BOTDA). A diversity scheme has been adopted, in which the BFS distribution along the same fiber is acquired at the two operating wavelengths. Based on the different wavelength scaling factor of temperature and strain coefficients, simultaneous measurement of strain and temperature at 1-m spatial resolution has been obtained in a proof-of-concept experiment.
Novel railway-subgrade vibration monitoring technology using phase-sensitive OTDR
Author(s):
Zhaoyong Wang;
Bin Lu;
Hanrong Zheng;
Qing Ye;
Zhengqing Pan;
Haiwen Cai;
Ronghui Qu;
Zujie Fang;
Howell Zhao
Show Abstract
High-speed railway is being developed rapidly; its safety, including infrastructure and train operation, is vital. This paper presents a railway-subgrade vibration monitoring scheme based on phase-sensitive OTDR for railway safety. The subgrade vibration is detected and rebuilt. Multi-dimension comprehensive analysis (MDCA) is proposed to identify the running train signals and illegal constructions along railway. To our best knowledge, it is the first time that a railway-subgrade vibration monitoring scheme is proposed. This scheme is proved effective by field tests for real-time train tracking and activities monitoring along railway. It provides a new passive distributed way for all-weather railway-subgrade vibration monitoring.
Distributed birefringence dispersion measurement for polarization-maintaining fiber based on optimization method
Author(s):
Zhangjun Yu;
Haoliang Zhang;
Jun Yang;
Yonggui Yuan;
Feng Peng;
Hanyang Li;
Changbo Hou;
Libo Yuan
Show Abstract
A measurement method of distributed birefringence dispersion (BD) for polarization-maintaining fiber is presented. This method is based on white light interferometry and optimization method. The sharpness function proposed in this paper is theoretically proved that will reach its maximum at the proper BD value. In addition, it is robust to noise demonstrated via simulation experiment. Eventually, the measurement result of average distributed BD for a 500m-long PMF coil with splicing points is -392.6 fs2/m and the relative error for every splicing point is less than 0.5‰.
Distributed fiber optic vibration sensor with enhanced response bandwidth and high signal-to-noise ratio
Author(s):
Dian Chen;
Qingwen Liu;
Xinyu Fan;
Zuyuan He
Show Abstract
A novel distributed fiber-optic vibration sensor (DVS) is proposed based on multi-pulse time-gated digital optical frequency domain reflectometry (TGD-OFDR), which can solve both the trade-off between the maximum measurable distance and the spatial resolution, and the one between the measurement distance and the vibration response bandwidth. A 21-kHz vibration is detected experimentally over 10-kilometer-long fiber, with a signal-to-noise ratio approaching 25 dB and a spatial resolution of 10 m.
Sweep BOTDA for fast distributed sensing
Author(s):
A. Minardo;
E. Catalano;
A. Coscetta;
L. Zeni
Show Abstract
A new scheme for fast distributed sensing based on Brillouin Optical Time-Domain Analysis (BOTDA) is proposed and demonstrated, based on the use of a frequency swept microwave source for the generation of the probe wave. The entire BOTDA measurement is taken within the duration of the frequency sweep, at a frequency granularity depending on the duration of the sweep, the repetition rate of the pump pulses and the number of averages.
Coherent-detection-assisted BOTDA system without averaging using single-sideband modulated local oscillator signal
Author(s):
Nan Guo;
Liang Wang;
Chao Jin;
Tao Gui;
Kangping Zhong;
Xian Zhou;
Jinhui Yuan;
Changyuan Yu;
Hwa-Yaw Tam;
Chao Lu
Show Abstract
A novel setup for coherent-detection-assisted Brillouin optical time domain analysis (BOTDA) is proposed and demonstrated. Performance enhancement is enabled by a power-controllable local oscillator (LO) generated using single-side-band (SSB) modulation. Through employing a commercial coherent receiver and polarization diversity scheme, the Brillouin gain traces carried on a stable intermediate frequency (IF) are obtained in real time without any averaging and processed by digital signal processing (DSP) without the need of ultra-narrow optical band pass filter. A spatial resolution of 4 m and frequency uncertainty of 1.473 MHz are achieved over 40 km sensing range using a single scan.
1.5-um low threshold, high efficiency Erbium-Raman random fiber laser
Author(s):
H. Wu;
Z. N. Wang;
W. Sun;
Q. H. He;
Y. J. Rao
Show Abstract
We report a low threshold, high efficiency random fiber laser with hybrid Erbium-Raman gain. The numerical analysis is made to describe the power performance of the proposed Erbium-Raman random fiber laser and reveal the high efficiency generation in this simple configuration. Thanks to the hybrid gain, the experimentally achieved laser threshold has been reduced to 60 mW. The optical conversion efficiency is of record high in the 1.5 μm regime, reaching 61.5% when pump power is 2 W. This work provides an effective way to generate high efficiency stable 1.5 μm random lasing, which could have important applications in optical fiber sensing and communication.
Polarization extinction ratio measurement for multi-functional integrated optic chip against birefringence dispersion and noise
Author(s):
Chengcheng Hou;
Zhangjun Yu;
Jun Yang;
Yonggui Yuan;
Feng Peng;
Hanyang Li;
Changbo Hou;
Libo Yuan
Show Abstract
We present a method for measuring polarization extinction ratio (PER) of multi-functional integrated optic chip (MFIOC) based on White light interferometry (WLI) against birefringence dispersion (BD) and noise. Instead of reading peak value, this method obtains PER via calculating the energy of the interferogram, which is theoretically proved that is independent of BD and proportional to the square of its peak value. In addition, the results of simulation demonstrate the method has an advantage of noise robustness versus the conventional peak value method. Eventually, experiment results of 100 measurements for a MFIOC are agree with the theory and simulation results.
Light-induced Au surface modification
Author(s):
Chunyang Han;
John Canning;
Kevin Cook;
Md. Arafat Hossain
Show Abstract
We show that the surface properties of Au thin films on a glass prism, typical of the Krestchsmann setup for SPR generation, can be modified or tuned with optical exposure. The wetting properties of the film were investigated by measuring contact angles of water drops at room temperature T = 23 °C. These contact angle change with optical irradiation from below the film. This change corresponds to a maximum contact angle reduction of Δθc ~ 30° when a surface plasmon resonance (SPR) is excited. The variation in contact angle during drop evaporation is evaluated under different irradiation conditions.
Broadband supercontinuum light source seeded by random distributed feedback fiber laser
Author(s):
R. Ma;
Y. J. Rao;
W. L. Zhang;
H. Wu;
X. Zeng
Show Abstract
A novel broadband light source based on supercontinuum (SC) generation seeded by random distributed feedback fiber laser (RFL) is proposed and demonstrated for the first time. A half-opened fiber cavity formed by FBG and TrueWave fiber is used to generate random lasing and SC simultaneously. Experimental results indicate that RFL can be used as an effective pump for generation of SC. SC with 20-dB bandwidth of >250 nm was obtained. Such a broadband SC light source seeded by RFL may pave a way to generate high power broadband RFLs for use in optical sensing and measurement.
Simultaneous measurement of dynamic strain and temperature distribution using high birefringence PANDA fiber Bragg grating
Author(s):
Mengshi Zhu;
Hideaki Murayama
Show Abstract
New approach in simultaneous measurement of dynamic strain and temperature has been done by using a high birefringence PANDA fiber Bragg grating sensor. By this technique, we have succeeded in discriminating dynamic strain and temperature distribution at the sampling rate of 800 Hz and the spatial resolution of 1 mm. The dynamic distribution of strain and temperature were measured with the deviation of 5mm spatially. In addition, we have designed an experimental setup by which we can apply quantitative dynamic strain and temperature distribution to the fiber under testing without bounding it to a specimen.
Fiber optic sensor based on polarization-dependent absorption of graphene
Author(s):
Liyun Ding;
Chuang Xu;
Zhilin Xia;
Bing Xu;
Jun Huang
Show Abstract
Graphene has been reported to show polarization-dependent optical absorption in the visible spectral range, that it shows more absorption for s-polarized light than p-polarized light. We study further on it and demonstrate that this unique property can be utilized to design a fiber optic sensor, which works in a similar way of surface plasmon resonance (SPR) fiber optic sensor. However, they are based on different mechanisms. Numerical simulation reveals that graphene layer of 5 nm is appropriate for the fiber optic sensor to achieve its best sensing performance, with a high sensitivity from 1700 to 6900 nm/RIU (refractive index unit).
An arm wearable haptic interface for impact sensing on unmanned aerial vehicles
Author(s):
Yunshil Choi;
Seung-Chan Hong;
Jung-Ryul Lee
Show Abstract
In this paper, an impact monitoring system using fiber Bragg grating (FBG) sensors and vibro-haptic actuators has been introduced. The system is suggested for structural health monitoring (SHM) for unmanned aerial vehicles (UAVs), by making a decision with human-robot interaction. The system is composed with two major subsystems; an on-board system equipped on UAV and an arm-wearable interface for ground pilot. The on-board system acquires impact-induced wavelength changes and performs localization process, which was developed based on arrival time calculation. The arm-wearable interface helps ground pilots to make decision about impact location themselves by stimulating their tactile-sense with motor vibration.
Modelling non-uniform strain distributions in aerospace composites using fibre Bragg gratings
Author(s):
Aydin Rajabzadeh;
Roger M. Groves;
Richard C. Hendriks;
Richard Heusdens
Show Abstract
In this paper the behaviour of fibre Bragg grating (FBG) sensors under non-uniform strain distributions was analysed. Using the fundamental matrix approach, the length of the FBG sensor was discretised, with each segment undergoing different strain values. FBG sensors that are embedded inside composites, also undergo such non-uniform strain distributions, when located in the vicinity of failures such as matrix cracks or delamination of layers. This non-uniform strain distribution was created in an experimental setup. Finite element analysis was used to analytically model the strain distribution along the FBG length. The measured FBG outputs were then compared to the simulated results. There was a high amplitude correlation between the results of the measured and the simulated reflection spectra with a maximum of 0.97 among all cases.
Wide-range dynamic strain measurements based on K-BOTDA and frequency-agile technique
Author(s):
Dengwang Zhou;
Yongkang Dong;
Benzhang Wang;
Hongying Zhang;
Zhiwei Lu
Show Abstract
We propose and demonstrate a novel fast Brillouin optical time-domain analysis system using the coefficient K spectrum which is defined as the ratio of phase-shift and gain of Brillouin amplification, where K features linear response, immune to the variation of pump power and a wide measure range. For a 30ns-square pump pulse, the frequency span of K spectrum can reach up to 200MHz. In dynamic strain experiment, a multi-slope assisted K-BOTDA with the measured strain of 5358.3με and the vibration frequency of 6.01Hz and 12.05Hz are demonstrated.
Non-contact vibration analysis using speckle-based techniques
Author(s):
I. Robles-Urquijo;
M. Lomer;
L. Rodriguez-Cobo;
J. M. Lopez-Higuera
Show Abstract
In this work, two different speckle based techniques are employed to quantify the movement of a vibrating surface. Directly projecting a coherent laser to a rough surface and collecting its associated subjective speckle using a high-speed camera, different frequencies are detected successfully. For the same purpose, a speckle pattern created by launching a coherent laser within a multimode fiber is employed as structured light to detect changes into the projection surface. The achieved results suggest that subjective speckle is better to analyze small sized areas, even at relative high frequencies, while projected speckle can give information about wider areas.
Application of FBG sensing technique for monitoring and early warning system of high-speed railway track conditions
Author(s):
Yongjia Zhang;
Fang Liu;
Yuhai Jing;
Weilai Li
Show Abstract
High-speed railway has achieved remarkable development in China, and safety monitoring of high-speed railway is becoming an important research. Fiber bragg grating (FBG) sensing technology is applied for monitoring and early warning system of high-speed railway track condition in this paper. The sensor network is built by putting FBG sensors on the high-speed rail tracks, which is necessary for real-time online monitoring of railway track temperature, displacement and strain. These different variables are collected, processed and analyzed by FBG demodulator. In addition, the railway track temperature prediction model are established based on relevance vector regression algorithm, which further improves the prediction accuracy and generalization performance. The system has been applied in the realtime online monitoring and early warning system of Guangzhou-Shenzhen-Hong Kong high-speed railway track condition. The system is running in good condition and playing an important role in early warning.
Extension of the dynamic range in slope-assisted coherent BOTDA sensors
Author(s):
Jon Mariñelarena;
Javier Urricelqui;
Alayn Loayssa
Show Abstract
We introduce a new technique to extend the dynamic range of coherent BOTDA sensors in dynamic measurements. It is based on launching pump pulses containing multiple frequencies so that the Brillouin spectra that they generate overlap, allowing to measure larger Brillouin frequency shift variations. Furthermore, this technique is compared to the procedure of shortening the length of the pulses, which also leads to a broadening of the spectra. We analyze both techniques, obtaining a threefold increase in range up to 400 MHz (±4000 με).
Feasibility study of strain and temperature discrimination in a BOTDA system via artificial neural networks
Author(s):
R. Ruiz-Lombera;
A. Piccolo;
L. Rodriguez-Cobo;
J. M. Lopez-Higuera;
J. Mirapeix
Show Abstract
Automatic discrimination between strain and temperature in a Brillouin optical time domain analyzer via artificial neural networks is proposed and discussed in this paper. Using a standard monomode optical fiber as the sensing element, the ability of the proposed solution to detect the known changes that the Brillouin gain spectrum exhibits depending on the applied temperature and/or strain will be studied. Experimental results, where different simultaneous strain and temperature situations have been considered, will show the feasibility of this technique.
Fiber interferometer combining sub-nm displacement resolution with miniaturized sensor head
Author(s):
Lun-Kai Cheng;
Ronald A. J. Hagen;
Lodi N. Schriek;
Peter M. Toet;
Oana E. Van der Togt
Show Abstract
The presented interferometer concept enables high-accuracy target displacement measurement in difficult accessible locations and the development of small fiber optic sensor to measure other physical parameters e.g. pressure, vibration, gravity force, etc.. Furthermore, this configuration is basically insensitive to disturbances to the lead fiber between the passive sensor head and the measurement system including the electro-optical parts and the detection interferometer. Two test setups are built and tested to demonstrate the feasibility of high-speed measurement up to 50 kHz, low system drift of ~0.5 nm over 500 s and a low displacement noise level down to 2.8 pm/√ Hz.
Brillouin optical time-domain analyzer with a fiber ring laser working on the SLM regime
Author(s):
R. Ruiz-Lombera;
L. Rodriguez-Cobo;
J. Mirapeix;
J. M. Lopez-Higuera
Show Abstract
In this paper we present the employment of an Erbium Fiber Ring Laser structure working on the Single Longitudinal Mode regime within a Brillouin optical time domain analyzer. An analysis of some key laser parameters will be carried out, proving that a very stable operation is achieved. The associated performance of the BOTDA system, as well as the possible benefits derived from the use of the proposed laser design will also be discussed.
Distributional measurement of effective refractive index differences of multimode fibers by Brillouin spectrum decomposition
Author(s):
Masashi Yokota;
Motoharu Miura;
Hiroki Watanabe;
Fumihiko Ito;
Ryo Maruyama;
Nobuo Kuwaki
Show Abstract
A novel method for distributionally evaluating the effective refractive index differences, Δneff, in multimode optical fibers is presented based on the Brillouin spectrum analysis. The proposed method is successfully demonstrated in GeO2-doped step-index 2-mode fibers, for evaluating Δneff between LP01 and LP11 modes, and the method could be straightforwardly expanded to fibers containing higher-order modes, by using a mode demultiplexer supporting the higher-order mode. To the authors’ best knowledge, this is the first report of distributional measurements of the effective refractive index differences in multimode optical fibers.
Coherent phi-OTDR based on polarization-diversity integrated coherent receiver and heterodyne detection
Author(s):
Qizhong Yan;
Ming Tian;
Xiang Li;
Qi Yang;
Yimin Xu
Show Abstract
We demonstrate a novel distributed optical fiber sensor system based on phase-sensitive optical time-domain reflectometry (Φ-OTDR). Both the phase and the amplitude of the Rayleigh scattering (RS) light can be demodulated based on I/Q demodulation and heterodyne detection using commercial available 100G integrated coherent receiver (ICR). The polarization fading problem in Φ -OTDR can be avoided by considering the RS signal from both polarizations. The dynamic strain sensing with a sensing range of 9.8 km and a spatial resolution of 15 m is experimentally demonstrated.
Spatially resolved measurement of arc flash event based on transmission loss of plastic optical fiber
Author(s):
Youngwoong Kim;
Hoonil Jeong;
Young Ho Kim;
Byung Sup Rho;
Myoung Jin Kim
Show Abstract
A novel scheme of plastic optical fiber (POF) based arc flash sensor capable of tracing arc event locations is presented. Incident position of flash light can simply be known by measuring the ratio of intensities at both fiber-ends, since the intensity of the flash light assisted by side-coupling of the fiber is generally attenuated a the fiber length. The arc flash sensor which can cover a wide range up to 10 m with a high spatial resolution of ±10 cm is experimentally demonstrated using the POF. Arc flash intensity can also be known by analyzing the coupled light intensity level at both fiber ends.
Suppression of stray interference peaks of optical joint in white light interferometer
Author(s):
Yongqing Cheng;
Jun Yang;
Yonggui Yuan;
Haoliang Zhang;
Zhe Yang;
Yan Lv;
Libo Yuan
Show Abstract
The stray interference peaks (SIPs) are an important factor resulting in the misjudgment of measurement information in white light interferometer (WLI). SIPs are generated by the residual reflected light beams. We theoretically analyze the interference conditions of the SIP. The analysis shows that these SIPs are discrete main interference peak outside and have different orders. We present a stagger optical path (SOP) method for suppressing or eliminating these SIP which will appear in the interference pattern. The SOP means that there is an appropriate fiber length determined by the delay amount of delay line between each joint. Moreover, an experiment with two joints, for simplicity, is given as an example. Experimental results show that the high-order SIP from the joints can be suppressed by the SOP to obtain a clean interference pattern.
Long-range distributed temperature sensing with sub-meter scale spatial resolution based on BOTDA employing pre-pumped Golay coding
Author(s):
Qiao Sun;
Shilin Sun;
Jianfei Wang;
Zhou Meng
Show Abstract
The BGS broadening caused by short pump pulse would degrade the SNR enhancement provided by the optical pulse coding and strongly reduce the measurement accuracy of coded BOTDA sensors, especially at long sensing ranges with sub-meter spatial resolution. In this work, to overcome this trade-off between spatial resolution and measurement accuracy, we implement a BOTDA sensor employing pre-pumped Golay coding with optimized pre-pumped pulse power. The proposed scheme fully exploits the SNR enhancement provided by the coding and the benefits from the preactivated acoustic field established by the pre-pumped pulse, achieving distributed temperature measurements with 70 cm spatial resolution and temperature resolution better than 1.5 °C throughout the 50 km sensing fiber.
Pulsed photothermal interferometry for high sensitivity gas detection with hollow-core photonic bandgap fibre
Author(s):
Yuechuan Lin;
Wei Jin;
Fan Yang;
Hoi Lut Ho
Show Abstract
Pulsed photothermal interferometry (PTI) gas sensor with hollow-core photonic bandgap fibre (HC-PBF) is demonstrated with a Sagnac interferometer-based phase detection system. Under the condition of constant peak pump power, the optimal pulse duration is found to be > 1:2 μs for detecting low-concentration of trace gases in nitrogen, limited by thermal conduction of gases within the hollow-core. Preliminary experiments with a 0.62-mlong HC-PBF gas cell, low peak power ( ~ 20:2mW) and a boxcar averager with 10k average times demonstrated a detection limit of 3:3 p:p:m acetylene. Detection limit down to ppb or lower is expected with high peak power pump pulses.
Singularity detection in FOG-based pavement data by wavelet transform
Author(s):
Dandan Yang;
Lixin Wang;
Wenbin Hu;
Zhen Zhang;
Jinghua Fu;
Weibing Gan
Show Abstract
The angular velocity data of Fiber-Optic Gyro (FOG) has been analyzed to locate the singularity by the wavelet transform (WT) method. By using WT analysis method to decompose and reconstruct the signal of pavement data collecting by the FOG, the different types of pavement singularities can be extracted. The experiments are conducted on different road surfaces. The experimental results show that the locations of bumps and expansion joints have been obtained, with a relative precision of 0.5 m and an absolute precision of 2 m over 2.4 km. The characteristic of the pavement roughness can also be identified.
How to specify and measure sensitivity in Distributed Acoustic Sensing (DAS)?
Author(s):
Haniel Gabai;
Avishay Eyal
Show Abstract
In Rayleigh-scattering-based Distributed Acoustic Sensing (DAS) an optical fiber is transformed into an array of thousands of 'virtual microphones'. This approach has gained tremendous popularity in recent years and is one of the most successful examples of a fiber-optic sensing method which made its way from the academia to the market. Despite the great amount of work done in this field, sensitivity, which is ones of the most critical parameters of any sensing technique, was rarely investigated in this context. In particular, little attention was given to its random characteristics. Without careful consideration of the random aspects of DAS, any attempt to specify its sensitivity or to compare between different DAS modalities is of limited value. Recently we introduced a new statistical parameter which defines DAS sensitivity and enables comparison between the performances of different DAS systems. In this paper we generalize the previous parameter and give a broader, simple and intuitive definition to DAS sensitivity. An important attribute of these parameters is that they can be easily extracted from the static backscatter profile of the sensing fiber. In the paper we derive the relation between DAS sensitivity and the static backscatter profile and present an experimental verification of this relation.
Fibre optic sensor based measurements of flow-induced vibration in a liquid metal cooled nuclear reactor set-up
Author(s):
B. De Pauw;
S. Vanlanduit;
K. Van Tichelen;
T. Geernaert;
H. Thienpont;
F. Berghmans
Show Abstract
Fuel assembly vibrations in nuclear reactor cores should not be excessive as these can compromise the lifetime of the assembly and lead to safety hazards. This issue is particularly relevant to new reactor designs that use liquid metal coolants. We therefore demonstrate accurate measurements of the vibrations of a fuel assembly in a lead-bismuth eutectic cooled installation with fibre Bragg grating (FBG) based sensors. The use of FBGs in combination with a dedicated sensor integration approach allows accounting for the severe geometrical constraints and providing for the required minimal intrusiveness of the instrumentation, identifying the vibration modes with required accuracy and observing the differences between the vibration amplitudes of the individual fuel pins as well as evidencing a low frequency fuel pin vibration mode resulting from the supports.
Strain and temperature measurement using a 9.5-m continuous chirped fiber Bragg grating with millimeter resolution
Author(s):
K. Fröjdh;
G. Hedin;
S. Helmfrid
Show Abstract
A 9.5-m continuous chirped fiber Bragg grating (CFBG) interrogated with an optical frequency domain reflectometer is used for strain and temperature measurements. The spatial resolution is 4 mm and the noise level is 0.1 K corresponding to 1 μstrain. The strain profile is also derived from the optical reflection spectrum alone, and the results are in good agreement with the profile obtained from the optical frequency domain reflectometer. A CFBG in combination with a high-resolution interrogator can therefore enable a cost-efficient continuous strain sensor.
An improved calibration method using third order polarization mode crosstalk for optical coherence domain polarimetry
Author(s):
Zhe Yang;
Jun Yang;
Haoliang Zhang;
Hanyang Li;
Feng Peng;
Yonggui Yuan;
Yongqing Cheng;
Libo Yuan
Show Abstract
We propose an improved optical coherence domain polarimetry (OCDP) calibration scheme by using polarization mode crosstalk (PMC). The scheme can be used to calibrate the OCDP system's measurement result about intensity of PMC. The intensity of 1st order PMCs are measured by polarization extinction ratio (PER) meter as the scale to transfer the standard into OCDP system, and the higher order PMCs formed by 1st orders are used to expand the scale. Specifying alignment angle of joint points and analyzer, we successfully use 3rd order PMCs and expand the range of calibration over -100 dB.
Determining the alarm signal in pulse interferometric fibre sensor by two independent criteria
Author(s):
Marek Życzkowski;
Mateusz Karol
Show Abstract
The article describes the construction and operation principle of the fibre optic pulse interferometer, which allows detection of mechanical disorders in fibre optic transmission line. Operation of this system is based on the optical pulses interference. Configuration of the system allows stable work of pulse interferometer over distances of several kilometres, with compensation impact of environmental conditions. Unique system detection capabilities obtained by using two independent criteria for alarm signal excitation. The aim of the research was to determine the usefulness of the proposed system to protection of information transmission via fibre-optic transmission networks.
Breaking through the bandwidth barrier in distributed fiber vibration sensing by sub-Nyquist randomized sampling
Author(s):
Jingdong Zhang;
Tao Zhu;
Hua Zheng;
Yang Kuang;
Min Liu;
Wei Huang
Show Abstract
The round trip time of the light pulse limits the maximum detectable frequency response range of vibration in phase-sensitive optical time domain reflectometry (φ-OTDR). We propose a method to break the frequency response range restriction of φ-OTDR system by modulating the light pulse interval randomly which enables a random sampling for every vibration point in a long sensing fiber. This sub-Nyquist randomized sampling method is suits for detecting sparse-wideband- frequency vibration signals. Up to MHz resonance vibration signal with over dozens of frequency components and 1.153MHz single frequency vibration signal are clearly identified for a sensing range of 9.6km with 10kHz maximum sampling rate.
The continuous line-shape measurement of bridge based on tri-axis fiber optic gyro
Author(s):
Liang Li;
Jianguan Tang;
Weibing Gan;
Wenbin Hu;
Minghong Yang
Show Abstract
The continuous three-dimensional curved track measurement system (CTMS) based on vehicular strapdown inertial navigation system (SINS) and four odometers is firstly presented and validated in order to achieve rapidly the long span curve measurement for bridge health monitoring. The line-shape measurement is conducted on a viaduct. Experimental results show that the Z-axis and Y-axis error in comparison with total station for 180 m curved viaduct are 6.39 cm and 37.16 cm respectively. The system which will be further improved has potential applications for bridge health monitoring in the future.
A fiber optic multi-stress monitoring system for power transformer
Author(s):
Dae-gil Kim;
Umesh Sampath;
Hyunjin Kim;
Minho Song
Show Abstract
A fiber-optic multi-stress monitoring system which uses 4 FBG sensors and a fiber-optic mandrel acoustic emission sensor is proposed. FBG sensors and a mandrel sensor measure different types of stresses occurring in electrical power transformer, such as temperature and acoustic signals. The sensor system uses single broadband light source to address the outputs of both sensors using single fiber-optic circuitry. An athermal-packaged FBG is used to supply quasi-coherent light for the Sagnac interferometer demodulation which processes the mandrel sensor output. The proposed sensor system could simplify the optical circuit for the multi-stress measurements and enhance the cost-effectiveness of the sensor system.
Increasing effective sensing points of Brillouin optical correlation domain analysis using four-wave-mixing process
Author(s):
Bin Wang;
Xinyu Fan;
Qingwen Liu;
Zuyuan He
Show Abstract
We propose a novel method to increase sensing points of Brillouin optical correlation domain analysis (BOCDA) by utilizing degenerated four-wave-mixing (FWM) process. A sinusoidally frequency-modulated lightwave is used as the pump of FWM, and the generated idlers have a broadened frequency modulation span. The idlers produced by FWM are used in BOCDA system to increase the sensing points of BOCDA since the number is proportional to the frequency modulation span of the laser source. We experimentally demonstrate a modulation span of 74 GHz by using the firstorder idler produced by FWM process, which is the largest frequency modulation span achieved in BOCDA system, doubling the sensing points of BOCDA from 1936 to 3872. It provides a possibility to use this method in the state-of-art BOCDA system to achieve several millions of effective sensing points.
Experimental demonstration of a Brillouin optical frequency-domain reflectometry (BOFDR) sensor
Author(s):
R. Ruiz-Lombera;
A. Minardo;
R. Bernini;
J. Mirapeix;
J. M. Lopez-Higuera;
L. Zeni
Show Abstract
To measure the strain and/or temperature along an optical fiber with one-end access, a Brillouin optical frequency-domain reflectometry (BOFDR) technique is presented in this paper. It is based on detecting the spontaneous Brillouin scattering from a sinusoidally modulated pump light. Compared to the Brillouin optical frequency-domain analysis (BOFDA), this new BOFDR sensor approach presents the advantage that the measurements are free from the distorting components related to acoustic wave modulation, thus simplifying the associated data processing.
Tuning refractive index sensing properties of micro-cavity in-line Mach-Zehnder interferometer with plasma etching
Author(s):
Monika Janik;
Marcin Koba;
Wojtek J. Bock;
Mateusz Śmietana
Show Abstract
This work presents an application of reactive ion etching (RIE) for an effective tuning of the spectral response and the refractive-index (RI) sensitivity of the micro-cavity in-line Mach-Zehnder interferometer (μIMZI). The μIMZIs were fabricated using femtosecond laser micromachining in a standard single-mode fiber as a form circular holes with a diameter of 54 μm. The application of RIE with SF6 and O2 used as reactive gas allows for an efficient and well controlled etching of the fabricated structure. The process resulted in cleaning the bottom of the micro-cavity and smoothening of its sidewalls. In transmission measurements, the effect of the plasma processing was observed as an increase in both spectral depths of the minima and RI sensitivity of the structure, as well as improved wettability of the micro-cavity surface, which made the measurements faster and easier.
High resolution temperature mapping of gas turbine combustor simulator exhaust with femtosecond laser induced fiber Bragg gratings
Author(s):
Robert B. Walker;
Sangsig Yun;
Huimin Ding;
Michel Charbonneau;
David Coulas;
Ping Lu;
Stephen J. Mihailov;
Nanthan Ramachandran
Show Abstract
Femtosecond infrared (fs-IR) laser written fiber Bragg gratings (FBGs), have demonstrated great potential for extreme sensing. Such conditions are inherent in advanced gas turbine engines under development to reduce greenhouse gas emissions; and the ability to measure temperature gradients in these harsh environments is currently limited by the lack of sensors and controls capable of withstanding the high temperature, pressure and corrosive conditions present. This paper discusses fabrication and deployment of several fs-IR written FBG arrays, for monitoring exhaust temperature gradients of a gas turbine combustor simulator. Results include: contour plots of measured temperature gradients, contrast with thermocouple data.
Optical fiber distributed sensing for high temperature superconductor magnets
Author(s):
Federico Scurti;
Justin Schwartz
Show Abstract
Over the last two decades, high temperature superconductors (HTS) have achieved performance and technical maturity that make them an enabling technology or an attractive solution for a number of applications like electric motors and generators, particle accelerators and fusion magnets. One of the remaining challenges that hinders a wide use of HTS and needs to be solved is quench detection, since conventional voltage based quench detection puts HTS magnets at risk. In this work we have developed and experimentally investigated the application of Rayleigh-backscattering interrogated optical fibers (RIOF) to the detection of normal zones in superconducting magnets. Different ways to integrate optical fibers into magnets are explored and the earlier detection of RIOF compared to voltage is demonstrated.
Combined long-period grating and micro-cavity in-line Mach-Zehnder interferometer for refractive index sensing
Author(s):
Monika Janik;
Marcin Koba;
Predrag Mikulic;
Wojtek J. Bock;
Mateusz Śmietana
Show Abstract
This work presents combined long-period grating (LPG) and a micro-cavity in-line Mach-Zehnder interferometer (μIMZI), both induced in the same single-mode optical fiber. In order to increase refractive index (RI) sensitivity of the LPG, it has been nanocoated with aluminum oxide (Al2O3). Next, the μIMZI has been fabricated as a cylindrical cavity (d = 60 μm) in the center of the LPG. In transmission measurements for various RI in the cavity and around the LPG we have observed two effects coming from two independently working sensors. There was no significant impact on one or the other in terms of their functional properties. Such a combination of sensorial effects can be applied for cross-reference measurements of the two different parameters at the same time or for discrimination of influence of other parameters on the RI measurements.
Study on the strain characteristic of fiber optic flexural disk accelerometer based on multilayer fiber coils
Author(s):
Feng Peng;
Yan Lv;
Shuaifei Tian;
Yaguang Geng;
Jun Yang;
Wenjing Chen
Show Abstract
The subject of this work is the strain characteristic of fiber-optic flexural disk accelerometer. In the presented investigation, the strain distribution of flexural disk is studied and the result shows that the position of fiber coil has a significant effect on the strain of fiber coil. We simulated the strain distribution of fiber-optic flexural disk accelerometer that based on multilayer fiber coils and on the optimized position. In experiment, corresponding sample accelerometer is fabricated and tested in the Brillouin Optical Time-Domain Analysis. The experimental result is in good agreement with the simulated result, provides this theoretical approach is effective in designing the fiber-optic flexural disk accelerometer.
Impact of the laser phase noise on chirped-pulse phase-sensitive OTDR
Author(s):
Juan Pastor-Graells;
María R. Fernández-Ruiz;
Hugo F. Martins;
Andres Garcia-Ruiz;
Sonia Martin-Lopez;
Miguel Gonzalez-Herraez
Show Abstract
In this work, the impact of the laser phase noise on chirped-pulse phase-sensitive OTDR signals is theoretically and experimentally analyzed. In particular, it is shown that the noise in the readings of strain/temperature changes along the fiber scales directly with the frequency noise power spectral density of the laser. The effect of the pulse chirp on the signal to noise ratio is also investigated. Three lasers with different linewidths (5 MHz, 50 kHz and 25 kHz), i.e., with different phase noise, were used for the experimental study, confirming the validity of the theoretical model.
Clarification of strain-temperature cross-sensitivity effect on Brillouin frequency shift in plastic optical fibers
Author(s):
Kazunari Minakawa;
Yosuke Mizuno;
Kentaro Nakamura
Show Abstract
The strain-temperature cross-sensitivity effect on Brillouin frequency shift (BFS) in plastic optical fibers (POFs) is fully investigated. First, we show that the strain coefficient of the BFS is dependent on temperature. In the strain ranges of 0– 1.2% and 4.0–9.0%, the temperature dependence is linear with coefficients of 1.5 MHz/%/°C and –0.4 MHz/%/°C, respectively. We then find that the temperature coefficient of the BFS is linearly dependent on strain with a coefficient of 1.5 MHz/°C/% in the strain range from 0 to 1.2%. For 4.0–9.0% strains, the BFS basically decreases with increasing temperature. These results indicate that temperature (and strain) compensation for the strain (and temperature) sensitivity of the BFS is required to correctly detect the strain and temperature magnitude in POF-based Brillouin sensing. We also show that temperature sensing with no sensitivity to strain is potentially feasible by using POFs pre-strained for >13%.
Optical thin film inspection using parallel spectral domain optical coherence tomography
Author(s):
Muhammad Faizan Shirazi;
Ruchire Eranga Wijesinghe;
Naresh Kumar Ravichandran;
Pilun Kim;
Mansik Jeon;
Jeehyun Kim
Show Abstract
The conventional Fourier domain optical coherence tomography system requires single scanner for two dimensional cross-sectional image and two scanners for volumetric image. Parallel spectral domain optical coherence tomography has advantage of single scanner for volumetric image, while two dimensional cross-sectional images are obtained by parallel acquisition of illuminated line on sample using area camera. In this study, the industrial inspection of optical thin film on touch screen panels was demonstrated using parallel spectral domain optical coherence tomography. The cross-sectional and volumetric images were acquired to detect the internal sub layer defects in optical thin film which are difficult to observe using visual or machine vision based inspection methods. The results indicate the possible application of the proposed system in touch screen panels inspection for quality assurance of product at consumer end.
Multi-point strain and displacement sensor based on intensity-modulated light and two-photon absorption process in Si-avalanche photodiode
Author(s):
Hiromasa Miyazawa;
Masaya Nemoto;
Yoshiki Yamada;
Yosuke Tanaka;
Takashi Kurokawa
Show Abstract
We propose a system for precise measurement of multi-point displacement and strain using fiber Bragg grating (FBG) sensors along with intensity-modulated light and two-photon absorption process in a Si-avalanche photodiode (Si-APD). This method sweeps both the optical wavelength and the phase difference between the two modulation signals. The FBGs’ reflection spectra and their change due to strain are successfully observed at the same time with the precision measurement of the FBG’s displacement, where the relative measurement uncertainty is 10-4. This fiber sensing system is especially suitable for structural health monitoring.
Slope-assisted Brillouin optical correlation-domain reflectometry using high-loss plastic optical fibers
Author(s):
Heeyoung Lee;
Neisei Hayashi;
Yosuke Mizuno;
Kentaro Nakamura
Show Abstract
We demonstrate high-speed distributed sensing based on slope-assisted (SA-) Brillouin optical correlation-domain reflectometry (BOCDR) using high-loss plastic optical fibers (POFs). Unlike the case of silica fibers, due to the gradual reduction in the transmitted power along the POF, the strain and temperature sensitivities are found to depend on sensing position. This unique effect is investigated both theoretically and experimentally, and then a correct POF-based distributed measurement is shown to be feasible by compensating this effect.
Effect of parameters in moving average method for event detection enhancement using phase sensitive OTDR
Author(s):
Yong-Seok Kwon;
Khurram Naeem;
Min Yong Jeon;
Il-bum Kwon
Show Abstract
We analyze the relations of parameters in moving average method to enhance the event detectability of phase sensitive optical time domain reflectometer (OTDR). If the external events have unique frequency of vibration, then the control parameters of moving average method should be optimized in order to detect these events efficiently. A phase sensitive OTDR was implemented by a pulsed light source, which is composed of a laser diode, a semiconductor optical amplifier, an erbium-doped fiber amplifier, a fiber Bragg grating filter, and a light receiving part, which has a photo-detector and high speed data acquisition system. The moving average method is operated with the control parameters: total number of raw traces, M, number of averaged traces, N, and step size of moving, n. The raw traces are obtained by the phase sensitive OTDR with sound signals generated by a speaker. Using these trace data, the relation of the control parameters is analyzed. In the result, if the event signal has one frequency, then the optimal values of N, n are existed to detect the event efficiently.
Highly sensitive distributed birefringence measurements based on a two-pulse interrogation of a dynamic Brillouin grating
Author(s):
Marcelo A. Soto;
Andrey Denisov;
Xabier Angulo-Vinuesa;
Sonia Martin-Lopez;
Luc Thévenaz;
Miguel Gonzalez-Herraez
Show Abstract
A method for distributed birefringence measurements is proposed based on the interference pattern generated by the interrogation of a dynamic Brillouin grating (DBG) using two short consecutive optical pulses. Compared to existing DBG interrogation techniques, the method here offers an improved sensitivity to birefringence changes thanks to the interferometric effect generated by the reflections of the two pulses. Experimental results demonstrate the possibility to obtain the longitudinal birefringence profile of a 20 m-long Panda fibre with an accuracy of ~10-8 using 16 averages and 30 cm spatial resolution. The method enables sub-metric and highly-accurate distributed temperature and strain sensing.
Towards efficient real-time submarine power cable monitoring using distributed fibre optic acoustic sensors
Author(s):
Konstantin Hicke;
Katerina Krebber
Show Abstract
Online condition monitoring of submarine power cables helps to avert failures and damages produced by mechanical impacts. We report, to our knowledge for the first time, on investigations regarding the feasibility of distributed fiber optic acoustic sensors based on C-OTDR, with the sensor fibers being embedded in the cable, to detect vibrations due to mechanical disturbances along the cable. We present first results of sensing experiments where acoustic signals are transmitted through water to simulate the corresponding submarine conditions. Furthermore, we show results evaluating the usefulness of fibre commonly embedded in existing power cable designs for our sensing purposes.
Effective light coupling in reflective fiber optic distance sensors using a double-clad fiber
Author(s):
Stefan Werzinger;
Lisa Härteis;
Aaron Köhler;
Rainer Engelbrecht;
Bernhard Schmauss
Show Abstract
Many fiber optic distance sensors use a reflective configuration, where a light beam is launched from an optical fiber, reflected from a target and coupled back into the fiber. While singlemode fibers (SMF) provide low-loss, high-performance components and a well-defined output beam, the coupling of the reflected light into the SMF is very sensitive to mechanical misalignments and scattering at the reflecting target. In this paper we use a double-clad fiber (DCF) and a DCF coupler to obtain an enhanced multimodal coupling of reflected light into the fiber. Increased power levels and robustness are achieved compared to a pure SMF configuration.
Dual-channel SPR fiber sensor by adjusting incident angle in fiber
Author(s):
Zongda Zhu;
Lu Liu;
Yong Wei;
Yaxun Zhang;
Yu Zhang;
Zhihai Liu
Show Abstract
We propose a novel dual-channel Surface Plasmon Resonance (SPR) fiber sensors based on the incident angle adjusting method. By grinding fiber tip to form wedge-shape with different angles, we can easier adjust the incident angle in fiber, and then the SPR wavebands will change corresponding. The simulation and experiment demonstrate that the SPR wavebands will red-shift with increasing of the fiber grinding angle. Based on this, we cascade two fiber tips whose grinding angles are 5° and 15° respectively. Under the tests of the refractive index (RI) range from 1.333 to 1.385, the SPR wavebands are 576~683nm and 677~955nm respectively. Therefore, we can demodulate SPR signal by wavelength division multiplexing (WDM) technology. Sequentially, we can detect two analytes simultaneously. This dual-channel SPR fiber sensor has important significance in the fields of multichannel liquid refractive indices and temperature selfreference measurements.
Demonstration of distributed shape sensing based on Brillouin scattering in multi-core fibers
Author(s):
Zhiyong Zhao;
Marcelo A. Soto;
Ming Tang;
Luc Thévenaz
Show Abstract
In this paper we demonstrate distributed shape sensing based on stimulated Brillouin scattering in a multi-core fiber (MCF). Brillouin optical time-domain analysis with differential pulse-width pairs is implemented to measure the local tangential strain-induced variation of the Brillouin frequency shift along different cores of the fiber. Employing the differential strain measured in multiple off-center cores in the MCF, distributed profiles of both bending angle and fiber curvature are parametrically retrieved. The paper presents the first demonstration of distributed bending sensing, providing the cornerstone to further develop the system into a fully distributed 3D shape sensor.
A new fiber optic accelerometer with push-pull structure using 3x3 coupler
Author(s):
Xiaokang Qiu;
Fei Liu;
Bin Xie;
Hongpu Zhou;
Duo Yi;
Xiangge He;
Xiaoping Zheng;
Min Zhang
Show Abstract
In this paper, we propose a new type of push-pull structure fiber optic accelerometer based on 3×3 coupler for the first time and carried out measurements of its responsivity and cross-axis sensitivity. With specific algorithm, the phase signal of the sensor can be extracted without complicated modulation and demodulation. Experiments show that the responsivity of the accelerometer is larger than 40dB (0dB ref 1rad/g) within the frequency band from 10Hz to 800Hz, which agrees well with the theoretical analysis. In addition, the cross-axis sensitivity can be optimized as low as about -30dB due to the push-pull structure. The results reported here indicate that this type of fiber optic accelerometer can be applied in vibration sensing such as micro seismic monitoring.
BOTDA sensing system employing a tunable low-cost Brillouin fiber ring laser pump-probe source
Author(s):
M. Iuliano;
D. Marini;
F. Bastianini;
G. Bolognini
Show Abstract
In this paper we show a Brillouin optical time-domain analysis (BOTDA) sensing system experiment employing a tunable narrow-linewidth dual pump-probe source based on modified Brillouin ring laser technology. The developed cost-effective source generates a pump-locked and tunable probe light, with wavelength shift and a large tuning range (~200 MHz), narrow linewidth (<2.5 MHz) and adequate power (~0.5 mW). The developed source was hence employed in BOTDA system experiments providing distributed sensing over ~10 km single mode optical fiber, and attaining strain and temperature resolutions of ~10με and ~0.5 °C respectively, indicating the pump-probe source as an efficient and cost-effective solution for BOTDA avoiding high-frequency signal generators or complex locking techniques.
High bending curvature withstanding one-dimensional angle sensor with fiber Bragg gratings
Author(s):
Minsu Jang;
Ockchul Kim;
Sungwook Yang;
Jinseok Kim
Show Abstract
We report on the development of an angle sensor which can measure at high bending curvature. Unlike the other sensors, the novel angle sensor can be durable and flexible. The sensors consist of one fiber Bragg grating (FBG) fiber which is located in the middle of each sensor, and are fabricated in varying thickness to confirm the relation between the distance of the center of the angle sensor to the core of the FBG node and the radii of curvature at which the sensor can measure. The thinnest sensor has the thickness of 200 μm and can measure at the bending radius of 5 mm. However, its angle measurement error is the largest with 1.25°, because of high sensitivity. Regulating the thickness of sensor, the angles at high curvatures can be measured reliably.
Eliminating the non-local effect in frequency-fixed probe wave based BOTDA sensor
Author(s):
Sheng Wang;
Zhisheng Yang;
Xiaobin Hong;
Wenqiao Lin;
Jian Wu
Show Abstract
The robustness of the BOTDA method based on dual-tone probe wave with fixed frequency separation is studied. It is verified that when the sensing fiber consists of two fiber segments with large Brillouin frequency shift difference (>100 MHz), the non-local effect would take place in the front fiber segment, which gives rise to frequency error on the determination of hotspot. Aiming at solving this problem, both the upper and lower probe sidebands are acquired simultaneously by using two photodiodes, and the average between the Brillouin gain and loss spectrum is calculated to eliminate the detrimental impact of the non-local effect.
A multicore compound glass optical fiber for neutron imaging
Author(s):
Michael Moore;
Xiaodong Zhang;
Xian Feng;
Gilberto Brambilla;
Jason Hayward
Show Abstract
Optical fibers have been successfully utilized for point sensors targeting physical quantities (stress, strain, rotation, acceleration), chemical compounds (humidity, oil, nitrates, alcohols, DNA) or radiation fields (X-rays, β particles, γ-rays). Similarly, bundles of fibers have been extremely successful in imaging visible wavelengths for medical endoscopy and industrial boroscopy. This work presents the progress in the fabrication and experimental evaluation of multicore fiber as neutron scattering instrumentation designed to detect and image neutrons with micron level spatial resolution.
Brillouin optical time domain analysis enhanced by tailored pump compensation
Author(s):
Young Hoon Kim;
Kwang Yong Song
Show Abstract
Brillouin optical time domain analysis (BOTDA) enhanced by the tailored compensation for the propagation loss of a pump pulse is experimentally demonstrated for long-distance and high-resolution distributed sensing. Distributed Brillouin amplification (DBA) of the pump pulse is applied in addition to an ordinary BOTDA configuration, where the frequency modulation with time-dependent amplitude variation is introduced to the DBA pump for tailored compensation for the propagation loss. In experiments, the distribution map of the Brillouin frequency along a 51.2 km test fiber is measured with a spatial resolution of 50 cm and a measurement error (σ) of less than 1 MHz.
Low velocity impact monitoring of composite wing structure under simulated wing loading condition using fiber Bragg grating sensors
Author(s):
Pratik Shrestha;
Yurim Park;
Hyunseok Kwon;
Chun-Gon Kim
Show Abstract
A low velocity impact onto a composite structure can result in the occurrence of barely visible impact damage (BVID), which is difficult to detect. Therefore, the low velocity impact monitoring of composite structures is highly desirable for impact detection and localization. In this paper, low velocity impacts on a composite wing under a simulated wing loading condition were monitored using six multiplexed fiber Bragg grating (FBG) sensors and localized using error outlier based impact localization algorithm. The impact response signals from the FBG sensors were sampled at a rate of 100 kHz using high-speed interrogator. The impacts were localized with an average error of 18.4 mm.
Spatial-division multiplexed hybrid Raman and Brillouin distributed sensor employing multicore fiber
Author(s):
Zhiyong Zhao;
Yunli Dang;
Ming Tang;
Li Duan;
Meng Wang;
Songnian Fu;
Weijun Tong;
Deming Liu
Show Abstract
Employing the multiple spatially independent channels offered by multicore fiber (MCF), spatial-division multiplexed (SDM) hybrid Raman and Brillouin distributed sensor has been demonstrated. The interrogation of Raman and Brillouin scattering are performed in distinct cores of the MCF, allowing for flexible management of the input powers between each of them, which is actually incompatible in hybrid Raman/Brillouin distributed system using single mode fibers (SMFs) due to the limitation of nonlinear effects. The proposed SDM system employs shared devices to generate pump pulse, but separate interrogation fiber channels. The combination of Raman and Brillouin sensing provides the capability of discriminative measurement between temperature and strain.
Long-distance delivery of multi-channel polarization signals in nuclear fusion research
Author(s):
Jinseok Ko;
Jinil Chung;
Kyuhang Lee
Show Abstract
A polarization-preserving optical system that includes a dual photoelastic modulator (PEM) has been designed and fabricated for the motional Stark effect (MSE) diagnostic system which measures internal magnetic field structures inside the tokamak for the Korea Superconducting Tokamak Advanced Research. The collection optics located outside the vacuum window is composed of four lenses, a dielectric coated mirror, and a dichroic beam splitter in addition to the PEM and a polarizer. The fiber dissector is designed based on the focal plane that aligns 25 lines of sight, each of which constitutes a bundle of 19 600-μm fibers. The fibers run about 40 m from the front optics in the tokamak vacuum vessel to the detector in the diagnostic area remote from the tokamak hall. This takes the advantage of the fact that the polarization information is intensity-modulated once going through the PEM and the polarizer. The polarization signals measured by the MSE diagnostic successfully demonstrates its proof-of-principle physics that is critical in the stable and steady-state operation of the tokamak plasmas.
Investigation of LEO environment exposure monitoring potential using embedded FBG sensors
Author(s):
Yurim Park;
Hyunseok Kwon;
Pratik Shrestha;
Chun-Gon Kim
Show Abstract
Composite materials provide many advantages over conventional materials including metals, especially for space applications. However, composites have failure modes that are complex and difficult to identify, and various cracks and delamination are predominantly difficult to detect visually. In this regard, an effective method of monitoring the integrity of composite materials and structures exposed to hazardous space environments is necessary to ensure the long-term reliability of composite materials in aerospace applications. FBG sensors are advantageous for space applications due to their immunity to various environments. In this study, FBG sensors were used to investigate LEO environment exposure monitoring of CFRP.
Distributed section-localization of an impact in a composite cylinder using the phase-sensitive optical time domain reflectometer
Author(s):
Khurram Naeem;
Yong-seok Kwon;
Il-Bum Kwon
Show Abstract
We demonstrate a distributed localization of an impact source in the composite cylinder using a home-made phase sensitive optical time domain reflectometer (Φ-OTDR). The system shows the advantages of simple configuration using semiconductor optical amplifier to improve the spectral response of the pump pulses, high spatial resolution and high signal-to-noise ratio (SNR). With a spatial resolution of 10 m, the SNR could be obtained as high as 6.5 dB. A composite cylinder is longitudinally divided in multiple sections of equal lengths by bending the sensing fibers around it at different locations, and the section of a source impact is localized using the time-delay of the signal detected by the sensing fibers.
GeAsSe chalcogenide slot optical waveguide ring resonator for refractive index sensing
Author(s):
N. Ashok;
Yeung Lak Lee;
WooJin Shin
Show Abstract
We present a slot optical waveguide ring resonator that can be used as a refractive index sensor. The proposed ring resonator works on the principle of coupling of the mode from the bus waveguide to the ring waveguide. The ring resonator was analyzed using the finite-difference time-domain method. Our proposed waveguide structure showed a sensitivity of 42 nm/RIU. Our aim is to design a chalcogenide ring resonator for refractive index sensing in midinfrared wavelengths.
Signal characteristics of the surface bonded fiber Bragg grating sensors by bonding length under different load types
Author(s):
Hyunseok Kwon;
Yurim Park;
Pratik Shrestha;
Chun-Gon Kim
Show Abstract
The surface-bonding method of the fiber Bragg grating(FBG) sensor is easier to handle than embedding method. However surface bonded FBG sensors have the limitation of the signal characteristics being affected by the bonding layer. In this study, the effects of the bonding length on the surface installed FBG sensor signal characteristics under various load types were empirically investigated. To evaluate the stability of the signal characteristics of the FBG sensors, the strain transfer rate and the multiple peaks ratio of the reflected spectrum were calculated and compared. From the experimental results, the strain transfer ratio and multiple peaks ratio varied because of the different strain gradients formed depending on the applied load type. Therefore, it was found that the effective bonding length for respective load types need to be determined to get a stable signal from the surface bonded FBG sensors.
Optical fiber end-facet polymer suspended-mirror devices
Author(s):
Mian Yao;
Jushuai Wu;
A. Ping Zhang;
Hwa-Yaw Tam;
P. K. A. Wai
Show Abstract
This paper presents a novel optical fiber device based on a polymer suspended mirror on the end facet of an optical fiber. With an own-developed optical 3D micro-printing technology, SU-8 suspended-mirror devices (SMDs) were successfully fabricated on the top of a standard single-mode optical fiber. Optical reflection spectra of the fabricated SU- 8 SMDs were measured and compared with theoretical analysis. The proposed technology paves a way towards 3D microengineering of the small end-facet of optical fibers to develop novel fiber-optic sensors.
Analytical expression and experimental validation of the Brillouin gain spectral broadening at any sensing spatial resolution
Author(s):
Mehdi Alem;
Marcelo A. Soto;
Moshe Tur;
Luc Thévenaz
Show Abstract
A novel and simple analytical expression to describe the Brillouin gain spectral broadening as a function of the spatial resolution in time-domain Brillouin distributed fiber sensors is deduced. The proposed model is experimentally validated using a pump-probe Brillouin sensing setup and also compared with numerical and approximate results. In addition, a compact mathematical form is presented for the peak gain reduction resulting from incomplete acoustic-wave activation in Brillouin sensors with short spatial resolution. Both mathematical expressions can be used together to quantitatively predict the impact of the spatial resolution on the signal-to-noise ratio and frequency uncertainty of the sensor.
Narrowing Brillouin gain spectrum for BOTDA sensor
Author(s):
Wenqiao Lin;
Zhisheng Yang;
Xiaobin Hong;
Sheng Wang;
Jian Wu
Show Abstract
A novel BOTDA method based on differential ∏-phase-shift-pulse pair is proposed for narrowing the Brillouin gain spectrum. Theoretical analysis and experimental results demonstrate that the proposal could achieve 17 MHz Brillouin gain spectrum linewidth with a fixed spatial resolution of 2.5 m. The Brillouin gain spectrum linewidth is 3 times narrower than that obtained using conventional single-pulse based BOTDA method with same spatial resolution, resulting in √3 times frequency accuracy improvement. Furthermore, the sharper rising/falling edge of the Brillouin frequency shift profile resulting from the narrowed Brillouin gain spectrum could obtain more precise temperature/strain information along the fiber.
Polarisation pulling in Brillouin optical time-domain analysers
Author(s):
Marcelo A. Soto;
Moshe Tur;
Alexia Lopez-Gil;
Miguel Gonzalez-Herraez;
Luc Thévenaz
Show Abstract
The impact of Brillouin scattering on the polarisation of pump and probe in a Brillouin optical-time domain analyser is investigated. Experimental results indicate that the Brillouin interaction integrated along the entire sensing fibre produces a polarisation pulling force that changes the pump polarisation. Although this force can be compensated to first order by dual-sideband probes, the Brillouin gain/loss experienced by probe bands induce a net pulling that leads to uncompensated polarisation fading and reduced signal-to-noise ratio. While the use of two simultaneous orthogonally-polarised probes alleviates fading issues, spectral distortions originate from the coupling between Brillouin gain and polarisation pulling.
Accurate determination of Brillouin frequency based on cross recurrence plot analysis in Brillouin distributed fiber sensor
Author(s):
Shahna M. Haneef;
K. Srijith;
D. Venkitesh;
B. Srinivasan
Show Abstract
We propose and demonstrate the use of cross recurrence plot analysis (CRPA) to accurately determine the Brillouin shift due to strain and temperature in a Brillouin distributed fiber sensor. This signal processing technique, which is implemented in Brillouin sensors for the first time relies on apriori data i.e, the lineshape of the Brillouin gain spectrum and its similarity with the spectral features measured at different locations along the fiber. Analytical and experimental investigation of the proposed scheme is presented in this paper.
Reducing sensitivity fading in C-OTDR by use of enhanced scattering fiber segments
Author(s):
René Eisermann;
Philipp Rohwetter;
Konstantin Hicke
Show Abstract
We present a technique to overcome the random transfer function of fiber-optic direct detection coherent optical time-domain reflectometry (C-OTDR). For this purpose, a standard optical fiber was treated by UV light in order to introduce local strongly scattering segments of definite size and distance to each other. Dynamic strain measurements were performed to demonstrate the sensory benefit in comparison to a non-manipulated fiber section. Our results show, that the modified fiber section exhibits a significant boost in strain sensitivity and in addition reduces the sensor dead time in a temperature-unstable environment as compared to a standard fiber.
Enlargement of measurement function in Brillouin optical correlation domain reflectometry with combining four performance improvement schemes
Author(s):
Ryu Shimizu;
Masato Kishi;
Kazuo Hotate
Show Abstract
We have demonstrated enhancement of measurement function in Brillouin Optical Correlation Domain Reflectometry (BOCDR) by totally combining, for the first time, four performance improvement schemes, which are double modulation scheme, temporal gating scheme, intensity modulation scheme, and phase modulation scheme. We have achieved distributed strain measurement with 10.1cm spatial resolution, over 5,280m measurement range, and 7,000μƐ strain dynamic range. The number of effective sensing points is over 52,200, which is the best result in BOCDR with wide strain dynamic range. We have also demonstrated the measurement with 3.94cm resolution over 5,280m range. The number of effective sensing points is over 134,000, which is the best result in all the BOCDR experiments reported so far.
Brillouin Standing Wave Reflectometry (BSWR): a novel approach for high sensitivity, fast and distributed strain sensing in optical fibers
Author(s):
A. Bergman;
M. Tur
Show Abstract
We demonstrate a novel distributed fiber sensing technique with a record broadband sensitivity of 10nƐ/√Hz at a sampling rate of 1MHz. A standing acoustic wave is generated by all-optical excitation of two simultaneously counter-propagating Brillouin dynamic gratings. A dual-tone readout probe pulse is used for the distributed measurement of strain-induced nonlinear phase-shifts of the acoustic wave. The phase is demodulated in electrical domain from the beat note of the reflected probe following the hardware-simpler direct detection. The measurement of 5kHz strain vibrations with a spatial resolution of 20cm (limited only by the 0.5ns switching time of our SOA) is reported.
Kilometer length low loss enhanced back scattering fiber for distributed sensing
Author(s):
Paul S. Westbrook;
Kenneth S. Feder;
Roy M. Ortiz;
Tristan Kremp;
Eric M. Monberg;
Hongchao Wu;
Debra A. Simoff;
Scott Shenk
Show Abstract
We demonstrate a 1km long optical fiber with continuous grating enhanced back scattering and attenuation close to standard single mode fiber. Scattering was observed to be more than 10dB above the Rayleigh back scattering of the optical fiber over a 10nm bandwidth between 1542 and 1552nm. The fiber attenuation was estimated to be 0.4dB/km. Our result was enabled through the fabrication of a standard single mode fiber with a UV transparent coating and reel to reel continuous UV grating inscription over more than 1km. We anticipate that enhanced scattering fiber will have impact in many sensor systems that rely on optical back scatter, including distributed acoustic sensing, security applications and structural health monitoring.
