There is a growing interest in developing compact and reliable sensors for molecular detection. Raman spectroscopy (RS) has the advantage of molecular specificity compared to other sensing techniques but lacks the required sensitivity. The development of surface enhanced Raman scattering (SERS) technologies has provided a solution to the sensitivity problem. In addition, the application of optical fibers, in conjunction with RS and SERS, has proved to be a unique platform for remote sensing, system integration, and further sensitivity enhancement. In this paper, we review our recent work on two types of optical fiber sensors for enhanced Raman gas detections. One is the hollow-core photonic crystal fiber (HCPCF) sensor utilizing the increased interaction volume by the light confinement inside the HCPCF. The other is the nanostructured optical fiber sensor, in which a multimode fiber facet is patterned with an array of metal-coated nanopillars, leading to surface-enhanced Raman scattering (SERS) that significantly increases the sensitivity. We demonstrate that these techniques can be well applied in the in-situ remote detection of organic vapors and explosives.

A novel class of polarization converters (PCs) in highly birefringent (Hi-Bi) microfibers is proposed and investi- gated numerically by use of the coded full vectorial finite difference beam propagation method. The novel PCs may be implemented by periodically deforming the surface along “one-side” of a Hi-Bi microfiber. Simulation shows that complete polarization may be achieved with a device length of less than 300 μm.

Fiber amplifiers such as Erbium-doped fiber amplifier (EDFA) played a key role in developing long-haul transmission system and have been an important element for enabling the development of optical communication system. EDFA amplifies the optical signal directly, without the optical-electric-optical switch and has the advantages such as high gain, broad band, low noise figure. It is widely used in repeaterless submarine system, smart grid and community antenna television system. This article describe the application of optical-fiber amplifiers in distributed optical fiber sensing system, focusing on erbium-doped fiber preamplifiers in modern transmission optical systems. To enhance the measurement range of a spontaneous Brillouin intensity based distributed fiber optical sensor and improve the receiver sensitivity, a two cascaded EDFAs C-band preamplifier with an optical bridge structure is proposed in this paper. The first cascaded EDFA is consisted of a length of 4.3m erbium-doped fiber and pumped in a forward pump light using a laser operating at 975nm. The second one made by using a length of 16m erbium-doped fiber is pumped in a forward pump light which is the remnant pump light of the first cascaded EDFA. At the preamplifier output, DWDM, centered at the signal wavelength, is used to suppress unwanted amplified spontaneous emission. The experimental results show that the two cascade preamplifier with a bridge structure can be used to amplify for input Brillouin backscattering light greater than about -43dBm. The optical gain is characterized and more than 26dB is obtained at 1549.50nm with 300mW pump power.

OPPC (Optical Phase Conductor) is a particular type of electric optical cables which composite the fiber unit into the structure of traditional phase lines. The special design fully leverages the power system's own line resources and achieves dual functions of power transmission and communication simultaneously, particularly in the power distribution networks. Furthermore, Raman optical time domain reflectometry (ROTDR) based distributed temperature sensing (DTS) system integrates with OPPC, that is to plant a single or several multimode optical fibers into the fiber unit of OPPC, which can realize the remote, online, continuous measure and location for the conductor’s temperature. This kind of monitoring system has many advantages such as anti-electromagnetic interference, information sensing and data transmission unification, long life-cycle, light weight, long transmission distance and non-power supply on site. But nonetheless, there is still a problem has to been resolved, that is whether the temperature of DTS fiber’s position represents exactly the one of OPPC’s. This article takes the section temperature field of 400/50 OPPC as the research object. Based on the temperature data measured by the Raman distributed temperature optical fiber sensor, a large number of finite element analysis and experiments are developed. The DTS measurement results under different actual working conditions of current-carrying capacity, wind velocity and environment temperature are quantitative analyzed. The changing rules and the relationships among the measurement results of DTS, the maximum and the surface temperatures of OPPC, and the results of numerical simulations and experiments have been proposed and demonstrated. On the whole, the main contributions of this paper are: (1) According to the structure of 400/50 OPPC, the Fluid-Structure Interaction (FSI) methodology and the steady section temperature field model are established which can reveal the OPPC’s temperature profile in multiple conditions; (2) Optical fiber Raman distributed temperature sensor is applied to measure the inner temperature of OPPC’s optical unit, and the measurement accuracy can be up to ±1°C; (3) A thorough experimental scheme is proposed that verified the correctness of the temperature field analysis approach, and also certified that the inner fiber catheter temperature and the maximum temperature of OPPC are consistent under common working conditions.

Verdet constants of beta-barium borate (BBO) and lead molybdate (PMO) crystals are measured experimentally by the method of comparison with a block of terbium-doped glass with a known Verdet constant. Experimental setups mainly include two prism polarizers, a solenoid and ac current supply, and signal processing circuits. The influences of light intensity fluctuation, applied magnetic field and signal processing circuits on measurement result of Verdet constant can be removed by using the method of comparison. For light wavelength of 635nm, the measured Verdet constants respectively are 5.80±0.06 rad/(T.m) for the BBO crystal and 54.6±1.1 rad/(T.m) for the PMO crystal. A novel optical current sensor based on electrooptic compensation is designed in principle using the BBO crystal.

Radiation-induced transmission loss in Low Water Peak Single Mode (LWPSM) fiber has been investigated. Formation and conversion processes of defect centers also have been proposed using electron spin resonance in the fiber irradiated with gamma rays. When the irradiation dose is low, Germanium electron center (GEC) and self-trapped hole center (STH) occur. With the increase of dose, E’ centers (Si and Ge) and nonbridge oxygen hole centers (NBOHCs) generate. With the help of thermal-bleaching or photo-bleaching, the radiation-induced loss of pre-irradiation optical fiber can be reduced effectively. The obtain results also have been analyzed in detail.

An optical temperature sensor based on Yb³⁺ and Er³⁺ codoped La2(WO4)3 phosphor for using in the high temperature region is discussed on the basis of fluorescence intensity ratio (FIR) method. The dependence of temperature on the upconversion green emission was intensive studied when the temperature increased from 300 K to 550 K under the excitation of 971 nm laser diode. The fluorescence intensity ratio of the two green emissions bands centered at 525 nm, 545 nm changed dramatically with the thermal treatment. By analyzing the experimental data according to the FIR method, the result on the thermometric property of La₂(WO₄)₃:Yb³⁺, Er³⁺ was obtained and it shows that the sensitivity of La₂(WO₄)₃:Yb³⁺, Er³⁺ reached the maximal value of about 0.0097 K-1 at the temperature of 510 K, even when the temperature was as high as 900 K, the sensitivity could still exceed 0.007 K-1. Results indicate that La₂(WO₄)₃:Yb³⁺, Er³⁺ has higher sensitivity for thermometry in high temperature area. Owing to its good thermal stability, low synthesis cost and high sensitivity, La₂(WO₄)₃: Yb³⁺, Er³⁺ phosphor has potential application in optical temperature sensing.

An analysis of highly birefringence low losss index-guiding phptonic crystal fiber composed of different sized circular air-holes in cladding and adjacent to the two ellipital air-holes x-diraction in the first inner rings is carried out in this work using voul fector finite element method.The birefringence properities in terms of various parameters,e.g,pitch length,air-hole size and ellipticity ratio are calculated.Form the numerical results confirm that the size control of these air holes and pitch length is the key to reaching high model birefringnce.The proposed struture at wavelength 1.55μm shows a birefringence of up to 3.02x10^-2 and at the same time can get the confinement loss of less than 1.9x10^-7dB/m, which is a reference significance in useful to dessign temperature sensors.

A wavelength dependent all-optical switching induced by side-mode injection locking behavior is experimentally demonstrated in single-mode Fabry-Pérot laser diode (SMFP-LD). The injection locking phenomenon is also observed while the peak wavelength at the injection beam is slightly shorter than that of the adjacent lasing mode, i.e. negative wavelength detuning, in which the obtained spectrum width is obviously extended compared to the case of positive wavelength detuning. As the wavelength detuning varies from ~0.35 nm to ~-0.2 nm with 3.5 dBm injection power, the on/off ratio of optical switching at dominated mode is remarkably decayed from ~50 dB to ~20 dB.

We fabricated MEMS-based optical fiber pressure sensor with anodic bonding. The vacuum-sealed microcavity with a thin silicon diaphragm is used as sensing element and its deformation characteristics determine the pressure measurement performance. Considering residual gas inside Fabry-Perot cavity and the thermal properties of material, we established a sensor’s temperature response mathematical model based on ideal gas equation and elastic theory. Temperature experiment of this sensor was carried out under vacuum. This work will provide a guide of temperature compensation process for achieving high precision pressure measurement.

In modern diesel engines, EGR (Exhaust Gas Recirculation) is an important technique used in nitrogen oxide (NOx) emission reduction. This paper describes the development and experimental results of a fiber-optical sensor using a 2.7 μm wavelength absorption to quantify the simultaneous CO₂ concentration which is the primary variable of EGR rate (CO₂ in the exhaust gas versus CO₂ in the intake gas, %). A real-time laser absorption method was developed using a DFB (distributed feedback) diode laser and waveguide to make optimal design and control of electronic EGR system required for ‘Euro-6’ and ‘Tier 4 Final’ NOx emission regulations. While EGR is effective to reduce NOx significantly, the amount of HC and CO is increased in the exhaust gas if EGR rate is not controlled based on driving conditions. Therefore, it is important to recirculate an appropriate amount of exhaust gas in the operation condition generating high volume of NOx. In this study, we evaluated basic characteristics and functions of our optical sensor and studied basically in order to find out optimal design condition. We demonstrated CO₂ measurement speed, accuracy and linearity as making a condition similar to real engine through the bench-scale experiment.

A fiber refractive index (RI) sensor based on a Mach–Zehnder interferometer (MZI) formed by sandwiching a thinned taper between two abrupt tapers. The abrupt tapers and the thinned taper are easily fabricated by a commercial fiber fusion splicer and a homemade tapering machine, respectively. The sensor has been experimentally demonstrated for RI sensing by monitoring its spectral shifts. The experimental results show that the sensor with a thinner taper has higher sensitivity due to the strong evanescent field interaction. A sensitivity of 3808.4 nm/RIU (refractive index unit) is obtained, which is about 100 times higher than that of the conventional taper-based MZI sensors.

In this paper we report the first stage field test results of a novel DFB fiber laser geophone system in Shengli oilfield. Two distributed feedback (DFB) fiber laser geophones are wavelength multiplexed and the space between them is 50m. The performance of DFB fiber laser geophones are tested by weak seismic signals stimulated by explosions together with conventional 20DX moving-coil geophones. The results show that the DFB fiber laser geophones have highly similarity with conventional geophones and higher bandwidth. The DFB fiber laser geophone system is promising in micro-seismic monitoring of unconventional oil and gas hydraulic fracturing.

Dielectrowetting is a powerful technique in manipulation of droplet. The key feature of dielectrowetting is the ability of a non-uniform and decay electric field to reversibly alter the energy balance of a droplet above a solid surface and change the contact angle of the droplet by employing microfabricated interdigitated electrodes. The contact angle versus voltage is presented and the effects of using different AC frequencies are also discussed. Special attention is dedicated to dielectrowetting-based light control system. The transmission spectrum of the light valve can be controlled with various voltages. This work facilitates us to improve and optimize the performance of light valve device operations.

A power-referenced fiber refractometer based on a hybrid fiber grating formed by a tilted-fiber Bragg grating (TFBG) cascading by a chirped-fiber Bragg grating (CFBG) is proposed and experimentally demonstrated. The optical signal reflected by the CFBG passes twice through the TFBG that enhances sensitivity of the refractometer. In addition, the optical signal is propagating all the way in the fiber core so that the extra insertion loss is low. Refractive index measurement with sensitivity up to 597.2 μW/R.I.U. is achieved within the range from 1.333 to ~1.42. The maximum detectable refractive index is ~1.45.

Steel cable plays an important role in modern infrastructure due to its special characteristics. Because most of structure load is transformed to the cable tension in cable stayed structures, it is very important to monitor cable tension. Being a slender element, Fiber Grating Strain Sensor is sensitive to axial strain and is regarded as a most prospective way to monitor the cable tension. The paper reviews a series of problems of FBG when embedded into the cable, and introduced five different embedded FBG strain sensors. Principle, characteristics, and application states of these five sensor has been discussed in details. The prospective of embedded FBG Strain Sensor for cable tension has been forecast.

We demonstrate a highly-sensitive current sensor by packaging a single taper-based modal interferometer into a copper tube that is filled with alcohol and surrounded with chrome-nickel wire. As the flowing current in the chrome-nickel wire is changed, the interference spectrum varies accordingly with sensitivity as high as 1014.5 nm/A² . Our results are promising for the current sensing and the electric-tunable filtering.

Smart Grid is a promising power delivery infrastructure integrated with communication and information technologies. By incorporating monitoring, analysis, control and communications facilities, it is possible to optimize the performance of the power system, allowing electricity to be delivered more efficiently. In the transmission and distribution sector, online monitoring of transmission lines and primary equipments is of vital importance, which can improve the reliability of power systems effectively. Optical fiber sensors can provide an alternative to conventional electrical sensors for such applications, with high accuracy, long term stability, streamlined installation, and premium performance under harsh environmental conditions. These optical fiber sensors offer immunity to EMI and extraordinary resistance to mechanical fatigue and therefore they will have great potential in on-line monitoring applications in Smart Grid. In this paper, we present a summary of the on-line monitoring needs of Smart Grid and explore the use of optical fiber sensors in Smart Grid. First, the on-line monitoring needs of Smart Grid is summarized. Second, a review on optical fiber sensor technology is given. Third, the application of optical fiber sensors in Smart Grid is discussed, including transmission line monitoring, primary equipment monitoring and substation perimeter intrusion detection. Finally, future research directions of optical fiber sensors for power systems are discussed. Compared to other traditional electrical sensors, the application of optical fiber sensors in Smart Grid has unique advantages.

Optical fiber sensor has great advantage for applications dealing with extreme environment. We developed a high precision optical pressure sensor for aviation industry. The optical pressure sensor is based on two-beam interference of microcavity and is fabricated with Micro-electromechanical systems (MEMS) and laser fusion technology. The cavity length variation resulting from external pressure is demodulated with spatial polarization low coherence interference unit and a high stable phase demodulation algorithm. The effect of light source output parameter is also investigated. We carried out research on optical fiber strain, temperature and acoustic vibration sensor for aerospace application. The optical fiber sensors for strain and temperature measurement are based on fiber Bragg grating(FBG).Both bare FBG and packaged FBG performances under cryogenic temperature and high vacuum are investigated. An eight-channel parallel FBG wavelength interrogator is developed. The optical fiber acoustic vibration sensor is based on two-beam interference of microcavity and use intensity demodulation method for high speed response. The mutiple-parameter and multiplepoint measurement instrument is successfully applied to status monitoring of water sublimator.

Fiber optic sensor network is the development trend of fiber senor technologies and industries. In this paper, I will discuss recent research progress on high capacity fiber sensor networks with hybrid multiplexing techniques and their applications in the fields of security monitoring, environment monitoring, Smart eHome, etc. Firstly, I will present the architecture of hybrid multiplexing sensor passive optical network (HSPON), and the key technologies for integrated access and intelligent management of massive fiber sensor units. Two typical hybrid WDM/TDM fiber sensor networks for perimeter intrusion monitor and cultural relics security are introduced. Secondly, we propose the concept of “Microstructure－Optical X Domin Refecltor (M-OXDR)” for fiber sensor network expansion. By fabricating smart micro-structures with the ability of multidimensional encoded and low insertion loss along the fiber, the fiber sensor network of simple structure and huge capacity more than one thousand could be achieved. Assisted by the WDM/TDM and WDM/FDM decoding methods respectively, we built the verification systems for long-haul and real-time temperature sensing. Finally, I will show the high capacity and flexible fiber sensor network with IPv6 protocol based hybrid fiber/wireless access. By developing the fiber optic sensor with embedded IPv6 protocol conversion module and IPv6 router, huge amounts of fiber optic sensor nodes can be uniquely addressed. Meanwhile, various sensing information could be integrated and accessed to the Next Generation Internet.

We present an effective method to compensate the spatial-frequency nonlinearity for polarized low-coherence interferometer with location-dependent dispersion element. Through the use of location-dependent dispersive characteristics, the method establishes the exact relationship between wave number and discrete Fourier transform (DFT) serial number. The jump errors in traditional absolute phase algorithm are also avoided with nonlinearity compensation. We carried out experiments with an optical fiber Fabry-Perot (F-P) pressure sensing system to verify the effectiveness. The demodulated error is less than 0.139kPa in the range of 170kPa when using our nonlinearity compensation process in the demodulation.

A demodulation algorithm for Low-coherence Interferometry is proposed. The demodulation includes a Lithium Niobate wedge, which index is tunable via optics-electric property. This method is based on the theorem that second harmonic term is orthogonal with the fundamental term in Fourier transform. An alternative external electric field is imposed on the wedge and tune the position of Low-coherence Interferometry is proposed. For every point on the CCD camera, the variation of the detected light power is Fourier transformed and obtains the ratio between second-harmonic term and fundamental term. This paper demonstrate theoretically that proposed demodulation method can enhance the accuracy of pressure sensing for more than 35 times.

The performance of attitude determination and control system using sun-sensor/magnetometer/gyro as attitude sensors would be impacted by the remanence of micro-satellite. To reduce the influences of remanence, a two-step Extended Kalman Filter (EKF) method is developed to estimate the steady magnetometer bias and residual magnetic moment. Firstly, the magnetometer bias is estimated. Then the magnetometer is calibrated with the estimation of magnetometer bias, and the corrected measurement is employed to estimate the attitude as well as the residual magnetic moment. Simulation results indicate that the accuracy of attitude determination is about 1° and the accuracy of magnetometer bias and magnetic moment estimation is about 10nT and 0.03A•m². The impact of remanence can be observably eliminated via the two-step EKF method.

Characteristic equations for eigenmodes in a planar waveguide which utilizes negative refractive index (NRI) material as a guiding layer and positive refractive index (PRI) materials as cladding layers have been deduced from the first principles in this work. Although the deduced characteristic equations for a NRI planar waveguide are just slightly modified compared with those of a PRI planar waveguide, they change the eigenmodes in the waveguide considerably. Firstly, the fundamental modes for both TE and TM polarization are excluded in a NRI planar waveguide; secondly, the first order modes in a NRI planar waveguide exhibit antisymmetric mode profiles (with their maxima and minima at the interfaces of guiding and cladding layers); finally, the modes of higher orders are trivial and of little interest. Although NRI materials that operate at optical frequencies are not available yet, evolvement of the metamaterial technique may provide us with such materials in the future and a NRI optical planar waveguide can be fabricated. With its unique features predicted by the characteristic equations (such as the maximal field strength at the interfaces of guiding and cladding layers for the first order modes), the NRI optical planar waveguide is of great potential to be used as highly sensitive sensing elements or non-plasmonic enhancement substrates for waveguide spectroscopy.

As a kind of photoelectrical imaging device, infrared thermal imaging system is widely used in the fields of industry, security, fire control and military etc. Infrared thermal imaging system is mainly used to detect the remote targets in the night and bad environmental condition. Therefore detection capability of infrared thermal imaging system to targets is key parameter under these applications. The technical factors and environmental condition affecting detection capability of infrared thermal imaging system are analyzed in this paper, and the theoretical method is set up on this basis. The detection capability of infrared thermal imaging system to targets on the sea is analyzed by the method, and compared with the real test results, the analytical results are proved to be correct.

Modern star sensors are powerful to measure attitude automatically which assure a perfect performance of spacecrafts. They achieve very accurate attitudes by applying algorithms to process star maps obtained by the star camera mounted on them. Therefore, star maps play an important role in designing star cameras and developing procession algorithms. Furthermore, star maps supply significant supports to exam the performance of star sensors completely before their launch. However, it is not always convenient to supply abundant star maps by taking pictures of the sky. Thus, star map simulation with the aid of computer attracts a lot of interests by virtue of its low price and good convenience. A method to simulate star maps by programming and extending the function of the optical design program ZEMAX is proposed. The star map simulation system is established. Firstly, based on analyzing the working procedures of star sensors to measure attitudes and the basic method to design optical system by ZEMAX, the principle of simulating star sensor imaging is given out in detail. The theory about adding false stars and noises, and outputting maps is discussed and the corresponding approaches are proposed. Then, by external programming, the star map simulation program is designed and produced. Its user interference and operation are introduced. Applications of star map simulation method in evaluating optical system, star image extraction algorithm and star identification algorithm, and calibrating system errors are presented completely. It was proved that the proposed simulation method provides magnificent supports to the study on star sensors, and improves the performance of star sensors efficiently.

A photonic crystal fiber sensor was prepared for refractive index sensing. Based on modal interferometer theory, the relationships between the refractive index of glycerine solution and resonant wavelength shift of the sensor are analyzed by numerical simulation. A fiber optical device was designed to operate the sensing experiment. The sensing experiment shows that the resonant wavelength blued-shift for the sensor with refractive index in the range of 1.33~1.41 happens when increasing glycerine solution from 0.0% to 50.0% (v/v). The experimental results are approximately consistent with theory.

A positioning system based on Mach-Zehnder optical fiber interferometer is proposed, which can sense vibration information along the circumference of the fiber sensor and hence be applied to positioning invasions as a safe-guard system in residence communities. A cross-correlation algorithm fulfilled with a DSP processor has been adopted to calculate the time difference of two channels of the Mach-Zehnder optical fiber interferometer. A signal identification algorithm is proposed to decrease the workload of the DSP when no vibration occurs. An experiment with 11.28 kilometers sensing fiber has been carried out, whose results show the Mach-Zehnder positioning system identifies the position of vibration instantaneously and has a 44 meters positioning error within the total sensing distance.

Pavement rut is one of the major highway diseases. In this article, the method of measuring rut based on laser triangulation is created. The rut-resolution model is established to design the parameters of optical system and the laser profile of road image was extracted by median filter and wavelet transform. An accurate calibration method on large field of view consisting of 28 sub-FOVs calibration and road profile reconstruction is also created. The process of calibration experiment and a new calculation method of rut is described. The measurement results were showed, which concluded the static test of gauge block and the dynamic measurement on highway. The conclusion is with this method using single CCD camera and two semiconductor laser of 808nm wavelength can reach the accuracy of 1mm on rut measurement in tough circumstance.

A subwavelength core microstructured optical fiber (MOF) temperature sensor based on infiltration with chloroform is proposed. Fiber core is surrounded by three large holes which can facilitate the infiltration of the chloroform. The refractive index of chloroform is sensitive to the temperature of the environment. Mode loss of the guided mode caused by index change of chloroform is obtained by solving Maxwell’s equation with finite element method (FEM), and is used as a criterion for sensitivity estimation. The relationship between the sensitivity of temperature sensor and the core diameter of MOF is investigated. Our simulation results show that the subwavelength core MOF is very promising for developing a linear response to temperature sensor of significantly reduced core size.

A U-shaped optical fiber sensing system designed to measure the refractive index of liquid had been proposed. The sensing mechanism of U-shaped optical fiber was discussed. A general single-mode fiber was bent into U-shaped and partially cladding of U-shaped fiber was corroded by HF acid buffer solution. Powers of different diameters of U-shaped fibers had been measured by many experiments. The results showed that the diameter of U-shaped fiber cladding 40 μm and the diameter of U-shaped was 1 cm were suitable to measure liquid refractive index. Then, this U-shaped optical fiber was immersed in liquid, such as pure water, ethanol, acetone and isopropanol, respectively. The evanescent field of the U-shaped fiber should be modulated by the liquid. The optical signal in the U-shaped fiber was measured with the optical spectrum analyzers(OSA). Finally, the experimental results were analyzed, and the spectra in the air was selected as a reference. The relative intensity was obtained for the different liquid. These results showed that the relative intensity of the liquid had a good linear relationship. This sensing device could accurately demarcate refractive index of liquid. It is simple, low cost, and it can also be applied in measuring the level of liquid.

For EMBCCD (Electron-Multiplying Back Illuminated CCD) which is low light level imaging device, EMBCCD high voltage multiplier clock driver circuit is the key to realizing EMBCCD chip gain function and low light imaging. Through the circuit software simulation, circuit board production and experimental testing, we observed high voltage multiplier clock driver waveform that meets the requirements. When this circuit was used in the integral low-light level imaging system, the luminance of the video on the monitor was strengthened. Then the amplitude of high-voltage drive waveform was adjusted, the video luminance changed along with the high voltage drive waveform amplitude.

Spectral imaging technology research is becoming more popular in the field of forensic science. Ultraviolet spectral imaging technology is an especial part of the full spectrum of imaging technology. This paper finished the experiment contents of the ultraviolet spectrum imaging method and image acquisition system based on ultraviolet spectral imaging technology. Ultraviolet spectral imaging experiments explores a wide variety of ultraviolet reflectance spectra of the object material curve and its ultraviolet spectrum of imaging modalities, can not only gives a reference for choosing ultraviolet wavelength to show the object surface potential traces of substances, but also gives important data for the ultraviolet spectrum of imaging technology development.

We demonstrate a novel fiber-optic hydrophone that use a fiber Bragg grating (FBG) as a sensing element. The operation principle is based on the modulation of birefringence of the FBG by high-frequency ultrasound. By measuring the amplitude of the first Stokes parameters of the transmitted light in FBG using a in line polarimeter, the amplitude and frequency of acoustic pressure can be determined. The FBG hydrophone has a linear response to acoustic pressure, and the sensitivity and dynamic range of the sensor are studied.

In this work, we present an optical fiber sensor system for remote refractive index measurement using the optical time domain reflectometry technique as an interrogation method, and investigate the refractive index sensibility of the sensor system in detail. The sensor system operates based on Fresnel reflection at the fiber’s end that is cleaved as a vertical planar surface. Surrounding refractive index from a long distance away can be measured easily through utilizing this sensor system. The experimental setup is simple and easy to handle. Experimental results show the feasibility of the remote measurement of refractive index. The range of this measurement can reach ~30km, moreover, to ensure its repeatability and accuracy, we retest the same sample for many times, some of which are artificially applied with disturbance. Lastly we make a comparative analysis to certify that the sensor system has a good potential to remote practical applications.

In this paper, a modal interferometer based on a simplified hollow-core PCF, which diffused with volatile organic compounds (VOCs) in the air holes, is proposed and investigated in our experiment. When light travels through the input single mode fiber and transmits into the simplified hollow-core PCF, there is only fundamental core mode. However, the high-order core modes will be excited when the molecules of VOCs diffuse into the air holes. After propagation of these modes in the simplified hollow-core PCF, they will recombine at the exit single mode fiber. The ethanol is chosen as the VOC sample in our experiments. The interference pattern of the interferometer, based on a 5.1 cm long simplified hollow-core PCF, exhibited fringe spacing of ~30 nm. The transmission intensity decreases while the fringe visibility increases as the ethanol concentration becomes larger, and the interference spectrum of the ethanol-diffused simplified hollow-core PCF modal interferometer has a red-shift, from 1542.96 nm at 250 ppm to 1545.52 nm at 1000 ppm. The modal interference proposed above has great potential as an optical fiber sensor, measuring physical parameters such as the concentration of VOCs.

With the development of sensor technology, wireless senor network has been applied in the medical, military, entertainment field and our daily life. But the existing available wireless senor networks applied in human monitoring system still have some problems, such as big power consumption, low security and so on. To improve senor network applied in health monitoring system, the paper introduces a star wireless senor networks based on msp430 and DSP. We design a low-cost heart-rate monitor senor node. The communication between senor node and sink node is realized according to the newest protocol proposed by the IEEE 802.15.6 Task Group. This wireless senor network will be more energy-efficient and faster compared to traditional senor networks.

This paper proposed a solution about low cost multi-channels Gallium Arsenide (GaAs) absorption-based fiber optic temperature sensing system, which can get specific channel temperature information at pre-set time slots by combining time division multiplexing technology and fiber optic multiplexing module. Established an seven channels fiber optic temperature sensing system using only one spectrum analysis unit and achieved -/+ 1°C temperature resolution, 2Hz measuring frequency at temperature range from 0°C to 150°C.

Partial discharges (PDs) are an electrical phenomenon that occurs within a transformer whenever the voltage stress is sufficient to produce ionization in voids or inclusions within a solid dielectric, at conductor/dielectric interfaces, or in bubbles within liquid dielectrics such as oil; high-frequency transient current discharges will then appear repeatedly and will progressively deteriorate the insulation, ultimately leading to breakdown. Fiber sensor has great potential on the partial discharge detection in high-voltage equipment for its immunity to electromagnetic interference and it can take direct measurement in the high voltage equipment. The energy released in PDs produces a number of effects, resulting in flash, chemical and structural changes and electromagnetic emissions and so on. Acoustic PD detection is based on the mechanical pressure wave emitted from the discharge and fluorescent fiber PD detection is based on the emitted light produced by ionization, excitation and recombination processes during the discharge. Both of the two methods have the shortage of weak anti-interference capacity in the physical environment, like thunder or other sound source. In order to avoid the false report, an all-fiber combined PD detection system of the two methods is developed in this paper. In the system the fluorescent fiber PD sensor is considered as a reference signal, three F-P based PD detection sensors are used to both monitor the PD intensity and calculate the exact position of the discharge source. Considering the wave band of the F-P cavity and the fluorescent probe are quite different, the reflection spectrum of the F-P cavity is in the infrared region, however the fluorescent probe is about 600nm to 700nm, thus the F-P sensor and fluorescent fiber probe can be connected in one fiber and the reflection light can be detected by two different detectors without mutual interference. The all-fiber partial discharge monitoring system not only can detect the PDs but also can ensure the position of the PD source and is of great anti-interference capacity in harsh environment.

Two signal multiplexing methods are proposed and experimentally demonstrated in optical time domain reflectometry (OTDR) for fault location of optical fiber transmission line to obtain high measurement efficiency. Probe signal multiplexing is individually obtained by phase modulation for generation of multi-frequency and time sequential frequency probe pulses. The backscattered Rayleigh light of the multiplexing probe signals is transferred to corresponding heterodyne intermediate frequency (IF) through heterodyning with the single frequency local oscillator (LO). Then the IFs are simultaneously acquired by use of a data acquisition card (DAQ) with sampling rate of 100Msps, and the obtained data are processed by digital band pass filtering (BPF), digital down conversion (DDC) and digital low pass filtering (BPF) procedure. For each probe frequency of the detected signals, the extraction of the time domain reflecting signal power is performed by parallel computing method. For a comprehensive performance comparison with conventional coherent OTDR on the probe frequency multiplexing methods, the potential for enhancement of dynamic range, spatial resolution and measurement time are analyzed and discussed. Experimental results show that by use of the probe frequency multiplexing method, the measurement efficiency of coherent OTDR can be enhanced by nearly 40 times.

Brillouin-based optical fiber sensing system has been taken more and more attentions in power transmission line in recent years. However, there exists a temperature cross sensitivity problem in sensing system. Hence, researching on strain separation technology of fiber brillouin sensing system is an urgent requirement in its practical area. In this paper, a real-time online distributed strain separation calculation technology of fiber Brillouin sensing combining an electric power optical fiber cable is proposed. The technology is mainly composed of the Brillouin temperature-strain distributed measurement system and the Raman temperature distributed measurement system. In this technology, the electric power optical fiber cable is a special optical phase conductor (OPPC); the Brillouin sensing system uses the Brillouin optical time domain analysis (BOTDA) method. The optical unit of the OPPC includes single-mode and multimode fibers which can be used as sensing channel for Brillouin sensing system and Raman sensing system respectively. In the system networking aspect, the data processor of fiber Brillouin sensing system works as the host processor and the data processor of fiber Raman sensing system works as the auxiliary processor. And the auxiliary processor transfers the data to the host processor via the Ethernet interface. In the experiment, the BOTDA monitoring system and the Raman monitoring system work on the same optical unit of the OPPC simultaneously; In the data processing aspect, the auxiliary processor of Raman transfers the temperature data to the host processor of Brillouin via the Ethernet interface, and then the host processor of Brillouin uses the temperature data combining itself strain-temperature data to achieve the high sampling rate and high-precision strain separation via data decoupling calculation. The data decoupling calculation is achieved through the interpolation, filtering, feature point alignment, and the singular point prediction algorithm etc. Testing in the laboratory and the transmission line test base all show that the simultaneous temperature and strain distribution measurement system can work effectively and reliably. This system provides a good solution reference to solve the temperature cross sensitivity problem in Brillouin-based optical fiber sensing system, and demonstrate a great practical value in power system applications.

Remote optical fiber sensors for radiation measurement are very useful in high radiation fields. In this paper, we fabricated scintillating optical fiber by using a cerium-doped silica rod. In the drawing process, we obtained different fiber samples by changing the drawing temperature and speed. The drawing temperature is from 1900 to 2200 °C and the speed is from 1 to 10 m/min. The experimental results showed that the optical rod physical properties such as viscosity, tension and scintillating efficiency can be controlled by the parameters of temperature and speed. The optical properties and chemical composition of the scintillating optical fiber have been analyzed by Raman spectra and X-ray fluorescence spectrometer (XRF-1800, SHIMADZU). The concentration of the doped cerium is 0.55%. Moreover, a test system is proposed to measure the scintillating performance of the fabricated optical fibers. For the scintillating properties, the effect of fiber length, the number of fiber bundle and the detection angle were analyzed. Experimental results showed that the optimal length of the cerium doped fiber is ~15 cm. The scintillating light intensity increases linearly with the number of the fiber bundle. With two low intensity ⁶⁰Co (0.2784 μCi) and ¹³⁷Cs (1.0865 μCi) gamma radiation sources, the scintillating light can be detected the gamma sources by using the scintillating fiber sensor which is connected a MMF.

The orthogonal interferometer based on 1/8 wave plate generates orthogonal signals by optical configuration. It is widely applied to interference system because of simple optical path and passive demodulation scheme for easy operation. But in the process of demodulation, the DC component of the signal needs to be eliminated. Because of the instability of light source and optical structure, the DC component of the signal may change over time. Therefore the circuit subtracting a constant can not thoroughly eliminate the DC component, causing the demodulation results are inaccurate. A improved demodulation algorithm is proposed in this paper. Theoretical analysis and experimental results show that, the demodulation method is almost not affected by the size of the DC component. When small deviation in DC component occurs, the demodulation results keep stable and accurate.

In order to realize the non-connect measurement on the power and character of jamming bomb, we carried out the research on power measurement device of jamming bomb based on Infrared Radiation. First, the power and infrared radiant band of the jamming bomb was summarized and refined. Then, ensuring the feature and power of jamming bomb was characterized by the magnitude of Infrared Radiation. Afterwards, based on the theory of the above, a power measurement device of Infrared Radiation was simulated and developed. Including the selection of detector and the detector application design, analog signal processing and digital signal processing, using correlation measurement method to detect and calculate the power of device. Finally, the specific method and advantage of the device was introduced. The results of the experiment show that: the response time of the device is less than 3ms; the detection sensitivity is better than 3 x 10⁸cm √HZ / W . The device successfully accomplished the accuracy measurement of Infrared Radiation between 1 to 20um wavelength with higher detection sensitivity and lower response time.

The fiber-optic Fabry-Perot pressure sensors have been widely applied to measure pressure in oilfield. For multi-well it will take a long time (dozens of seconds) to demodulate downhole pressure values of all wells by using only one demodulation system and it will cost a lot when every well is equipped with one system, which heavily limits the sensor applied in oilfield. In present paper, a new hybrid demodulation method, combining the windowed nonequispaced discrete Fourier Transform (nDFT) method with segment search minimum mean square error estimation (MMSE) method, was developed, by which the demodulation time can be reduced to 200ms, i.e., measuring 10 channels/wells was less than 2s. Besides, experimental results showed the demodulation cavity length of the fiber-optic Fabry-Perot sensor has a maximum error of 0.5 nm and consequently pressure measurement accuracy can reach 0.4% F.S.

The subway is a representative form of the rail transit, and its catenary suspension system is a very important aspect to the safety of the whole system. The safety monitoring of the subway catenary suspension system is studied in this paper. A demonstrate model is set up in the laboratory, and some fiber Bragg grating (FBG) sensors including strain sensors and displacement sensors were utilized in the demonstrate system. It is shown that the used sensors could indicate the safety information of the system effectively. Especially, the designed displacement sensor that is packaged by athermal technique can abandon the influence of the environment temperature in a certain degree. Its engineering applicability is greatly improved.

In this paper, we described a distributed strain measurement scheme in one-dimensional. The sensing information of FBG is demodulated by a CCD spectrometer, the discrete strain is achieved by fitting and processing discrete signal demodulated utilizing labVIEW virtual instrument technology. Then it could be achieved by Using polynomial fitting method to one-dimensional discrete strain distributed detection. Experimentally, measurement was implemented in Cantilever to prove the system performance. The experimental result shows that the system can reflect the strain distribution in one-dimensional and an order strain modal characteristics of cantilever accurately. The detection system can achieve real-time and dynamic measurements, the response time for 2kHz, the response accuracy for 4μ(epsilon).

Optoelectronic electric field sensor (OEFS) is an important device for intensive electric field measurement. Relative humidity (RH) poses important impact on the stability of OEFS. To study thoroughly how RH influences OEFS’s stability and find solutions to avoid the influence is significant. In this paper, an experimental system to study how RH influences OEFS’s stability was built. A series of experiments showed high humidity affected the low frequency response of the sensor- amplitude attenuation and phase shift. The analysis of the results showed that the water film were the key influence factors of the RH stability of OEFS and hydrophobic treatment of the shell could improve the stability of the sensor from the effect of RH. Further experiments verified its correction.

A novel all-fiber Mach-Zehnder modal interferometer (MZMI) for temperature and strain measurements is demonstrated. The interference between the core and the cladding modes in the single mode fiber (SMF) is utilized. To excite the cladding modes, a microcavity is embedded in the SMF. After propagating a distance in the cladding, the cladding modes will couple back to the core mode at the other point fabricated by core-offset splicing. The MZMI exhibits a high temperature sensitivity (<0.1nm/ °C) in the range of 200-600 (°C). The strain response of the MZMI is also investigated. This compact, simple and cost-effective MZMI owns potential applications in temperature and strain measurements.

Satellite laser altimeter can not only accurately measure the surface elevation of target, but also carry characters of target surface on its return waveform. The return signals interacted by coastal zones and transmitted signal are simulated in this paper, large number of return signal waveforms of Geoscience Laser Altimeter System are analyzed, and the change rules of return signal waveforms of coastal zones relative to sea surface are concluded, which are peak decreasing, pulse width widening, and mostly bimodal pattern. It is concluded that extracting coastline and locating the deserted island are feasible with this method of analyzing return waveforms of laser altimeter.

In this thesis, the authors discuss the detection performance of the small-scale precision engineering with the Brillouin scattering light on the base of experiments. The authors made the measurements using the traditional Strain Distribution Gauge and optical fiber scattering light shift equipment AQ8603 and obtained two results. The authors compared and analyzed the data and made the conclusion that the BOTDR technology is not suitable for the small-scale Precision Engineering. The wiring methods and their effects to detection performance are also been discussed in this thesis.

OPGW(Optical Fiber Composite Overhead Ground Wire) is an important part of high voltage transmission lines with characteristics of wide distribution and long distance. It is difficult for routine inspection and status detection by traditional method. So, it is necessary to monitoring the status of OPGW using distributed optical fiber strain and temperature measurement device. In this paper, the strain and temperature calibration experiment of composite optical fiber in OPGW was completed using BOTDR (Brillouin Optical Time Domain Reflectometry). The difference of Brillouin frequency shift coefficients to strain and temperature and initial frequency shifts between different optical fibers were compared. The method to accurately locate connections was provided using distributed Brillouin frequency shift curves. The status monitoring for running OPGW was realized and the data was analyzed. Results indicate that, the frequency shift coefficients to strain and temperature of single mode fibers in one OPGW are almost the same, which are 0.05MHz/μ(epsilon) and 1.05MHz/°C, but the initial frequency shifts are different with 20MHz range. The Brillouin frequency shifts at fiber connections in change obviously, which can serve as locating basis for connections. The topography, span, mark-height and climate affect the strain and temperature distribution of OPGW.

We carried out distributed measurements of the parametric Brillouin gain using a sensing technique based on an Brillouin optical time-domain analysis. Using this distributed technique, we study the influence of the polarization mode dispersion (PMD) of the single mode fiber (SMF) to the Brillouin parametric gain spectrum. It is found that the shape of the obtained spectrum depend on the local birefringence of the fiber.

An optical fiber laser salinity sensor based on multimode interference effect is proposed and demonstrated. The sensor head manufactured by splicing a section of no-core fiber (NCF) between two single-mode fibers possesses a transmission peak at a certain wavelength due to multimode interference effect. Salinity of the liquid it immerges can be measured from wavelength shift the transmission peak. Enhanced measurement accuracy is achieved by inserting the sensor head into the cavity of an erbium-doped fiber ring laser, because the laser’s linewidth is much narrower than that of the transmission peak. Linear response with salinity sensitivity of 19.4 pm/% has been achieved and the measurement range is from 3.86% to 21.62%.

A new fully distributed optical fiber sensing and location technology based on the Mach-Zehnder interferometers is studied. In this security system, a new climbing point locating algorithm based on short-time average zero-crossing rate is presented. By calculating the zero-crossing rates of the multiple grouped data separately, it not only utilizes the advantages of the frequency analysis method to determine the most effective data group more accurately, but also meets the requirement of the real-time monitoring system. Supplemented with short-term energy calculation group signal, the most effective data group can be quickly picked out. Finally, the accurate location of the climbing point can be effectively achieved through the cross-correlation localization algorithm. The experimental results show that the proposed algorithm can realize the accurate location of the climbing point and meanwhile the outside interference noise of the non-climbing behavior can be effectively filtered out.

Coupling error is one of the main error sources of the quartz tuning fork gyroscope. The mechanism of capacitance coupling error is analyzed in this article. Finite Element Method (FEM) is used to simulate the structure of the quartz tuning fork by ANSYS software. The voltage output induced by the capacitance coupling is simulated with the harmonic analysis and characteristics of electrical and mechanical parameters influenced by the capacitance coupling between drive electrodes and sense electrodes are discussed with the transient analysis.

A fiber inline Michelson interferometer fiber optic sensor was presented for sensing applications, including high temperature performance and refractive index change. The sensor was fabricated using one-step femtosecond (fs) laser micromachining technique. A step structure at the tip of a single mode optical fiber was formed during the micromachining process. The device had a loss of 16 dB and an interference visibility exceeding 18 dB. The capability of this device for temperature sensing up to 1000 °C and refractive index sensing application in various concentrations of ethanol solution were all demonstrated.