光纤光栅传感器波长移位检测方法

光纤光栅波长移位检测是光纤光栅传感器的核心技术之一,已提出的光纤光栅波长移位检测方法有被动解调法、匹配光栅法、非平衡Mach-Zehnder干涉仪法、可调谐窄带光源法和激光锁模法等详细介绍了光纤布拉格光栅(FBG)传感器的波长移位检测方法,分析了各种检测方法原理.重点讨论了非平衡M-Z干涉仪法和可调谐窄带光源法,并对以上各种方法的优、缺点进行了分析和讨论.     

基于Bitaper-LPFG-Bitaper结构的全光纤Mach-Zehnder干涉仪的温度传感特性

提出并制作出一种基于锥体光纤-长周期光纤光栅-锥体光纤结构的全光纤Mach-Zehnder(M-Z)干涉仪传感器,并对其温度传感特性进行了研究.实验结果表明,固定光纤锥体和长周期光纤光栅的结构,仅改变两个光纤锥体之间的距离,对应不同的M-Z干涉谐振峰呈现出不同的温度传感特性:随着两个光纤锥体之间的距离增加,位于短波长处的谐振峰,传感器的温度灵敏度减小,而位于长波长处的谐振峰,传感器的温度灵敏度增加.当传感器长度为16.5 cm时,在1 680 nm附近的温度灵敏度达到0.102 06 nm/℃.实验结果对于锥体光纤-长周期光纤光栅组合型温度传感器的优化设计具有重要参考价值.     

光纤法布里-珀罗干涉温度压力传感技术研究进展

光纤法布里-珀罗干涉温度和压力传感器具有灵敏度高、制作简单、成本低、体积小和抗电磁干扰能力强等优点,已被广泛应用于军事和民用领域.在某些环境恶劣,如具有强电磁干扰和腐蚀性,或提供给传感器的安装空间非常有限的特殊工业领域,微型光纤温度和压力传感器发挥着重要的作用,国内外诸多高校、科研院所都在对其进行研究.本文综述了光纤法布里-珀罗干涉仪的基本原理、制备技术、及其压力和温度传感应用的研究进展.详细介绍了湿法化学腐蚀制备法、电弧放电制备法、飞秒激光制备法、聚合物辅助制备法等常见光纤法布里-珀罗腔传感器的制作工艺,分析了不同制作工艺的优缺点;详细介绍了光纤法布里-珀罗干涉仪在温度传感、压力传感和温压一体传感领域的应用;最后对光纤法布里-珀罗干涉温度压力传感器的发展进行了总结和展望.     

相位调制全光纤Mach-Zehnder干涉仪传感实验

使用单模石英光纤设计了相位调制全光纤M-Z干涉仪传感实验系统,采用CCD技术显示干涉条纹的空间分布及其移动情况,同时利用光电检测及可逆计数技术实现移动条纹的自动计数.利用该系统进行了光纤温度传感、光纤应变传感原理性实验测试.     

蓝宝石光纤及其高温传感器

单晶蓝宝石光纤具有热稳定性好、机械性能强、化学性能稳定等优点,在高温、高压等恶劣环境中的应用受到广泛关注.介绍了单晶蓝宝石光纤的制备方法、基本特性及高温传输特性.重点讨论了目前基于单晶蓝宝石光纤制备的高温传感器件,包括法布里-珀罗干涉仪、布拉格光栅、以及迈克尔逊干涉仪,并分析了这些传感器的制备方法和工作原理.最后针对单晶蓝宝石光纤与传统单模光纤难兼容的问题,介绍了蓝宝石衍生光纤的制备及其传感器的最新进展,并展望了未来蓝宝石光纤的发展方向.     

少模光纤模式反射迈克尔孙干涉仪及其游标增敏应用

提出了一种少模光纤迈克尔孙干涉仪（MI）级联法布里-珀罗干涉仪（FPI）的游标增敏折射率传感器。少模光纤MI用作参考干涉仪,开放腔FPI作为传感干涉仪,解决了传统双FPI传感器的参考干涉仪制备复杂、可控性差的问题。仿真研究了单模-少模光纤错位量对少模光纤模式激发效率的影响,以及少模光纤长度对增敏倍数的影响。基于仿真优化参数制备了少模光纤MI-FPI传感器,并测试了其折射率响应特性,分析了增敏极限及限制因素。该传感器在1.3384～1.3412的折射率范围内的折射率灵敏度达到12466.956 nm/RIU（灵敏度单位）,相对于无MI级联的单个FPI传感器提升了12.29倍,放大倍数可基于少模光纤长度灵活控制。该方法使传感器的增敏效果显著、增敏倍数可控、制备方法简单且光谱稳定性好,在折射率传感领域具有潜在的应用价值。     

光纤Fizeau干涉仪的声发射检测研究

验证了一种基于光纤Fizeau干涉仪的声发射传感器,可用于固体表面传播的超声波的检测.这种传感器的特点是能够精确地检测由固体表面传播的超声波产生的微弱振动.当超声波信号通过光纤传感器到达探测器时,干涉仪的输出光强度受到了超声信号的调制.通过检测干涉仪的输出光强度并利用Fourier变换,测得了超声信号的振幅和频率.对传感系统的相位调制特性进行了仿真,并对实验结果进行了分析.     

单轴分布式光纤传感器管线泄漏探测方法及定位理论分析

利用Sagnac干涉原理的分布式光纤传感器是一种可用于长途油气管线侵入、泄漏探测和定位的新技术.为了克服屏蔽和隔离Sagnac光纤环中未用作传感的那一半光纤所带来的屏蔽困难、成本增加等问题,提出一种单轴分布式光纤传感器的方法.其原理是利用一条光纤代替光纤环,并在光纤尾端设置法拉第旋转镜,构成偏振无关Sagnac干涉仪探测和定位管线泄漏.文中详细分析和讨论了该方法的系统光路和探测定位原理.     

基于多芯光纤级联布喇格光纤光栅的横向压力与温度同时测量

提出并制作了一种基于多芯光纤与单模光纤错位构成的马赫-曾德尔干涉仪,将其与光纤布喇格光栅级联,形成的全光纤传感系统可实现横向压力和温度双参量同时测量.马赫-曾德尔干涉仪是利用多芯光纤和单模光纤的模场不匹配而发生模间干涉,当外界横向压力直接作用在多芯光纤内部光场,干涉仪具有较高的灵敏度.实验结果表明:马赫-曾德尔干涉仪压力灵敏度为28.57nm/(N·mm~(-1)),线性度为0.997,而光纤布喇格光栅在一定范围内对压力变化不敏感;马赫-曾德干涉仪和光纤布喇格光栅对温度变化都具有较高的线性度,温度灵敏度分别为56.1pm/℃和11.3pm/℃.对于分辨率为0.02nm的光谱仪,传感器可实现的压力和温度测量分辨率分别为7.0×10~(-4)N/mm和0.03℃.马赫-曾德尔干涉仪的透射谱和光纤布拉光栅的谐振峰对横向压力和温度的变化有不同的光谱响应,利用光谱仪对传感器的透射谱实时监测,方便地实现了压力与温度双参量的测量.该传感器结构简单,灵敏度高,可用于不同领域的压力传感.     

超低温度系数的光子晶体光纤Sagnac压力传感器

 提出了一种基于光子晶体光纤Sagnac干涉仪的横向压力传感器。使用的光子晶体光纤为低双折射光纤,首先预先在Saganc环中的光子晶体光纤上施加初始压力,使Sagnac干涉仪产生正弦干涉光谱,然后再将被测物体放在光子晶体光纤上,由于被测物体重力的作用,Saganc干涉仪输出的光谱产生移动,实现横向压力传感测量。传感器具有高灵敏度0.529 nm/(N·mm)及超低的温度系数-0.4 pm/℃,其环境温度的影响可以忽略。     

All-fiber optic acoustic sensor based on multimode-single mode-multimode structure

A simple and low cost optical fiber acoustic sensor based on multimode-single mode-multimode (MSM) fiber structure is presented. The optical coupling efficiency between hetero-core fibers spliced structure is modulated by acoustic pressure through a thin metal foil. Acoustic wave is detected by measuring the intensity change of transmission light. Experiments are carried on to testify the performance of MSM fiber acoustic sensor and the experimental results show that the acoustic wave can be sensitively detected within 11 kHz frequency range.     

Surface-bonded fiber optic Sagnac sensors for ultrasound detection

This paper describes a fiber optic sensor suitable for remote sensing and multi-point detection of ultrasound. This ultrasound sensor is based on the surface-bonded fiber optic Sagnac interferometer with the output fringe visibility of 1; it consists of a laser source, an ordinary single mode fiber delay line, a fiber coupler, a phase modulator and polarization controllers. For the validation of the sensor, surface acoustic waves and Lamb waves are excited by illuminating a steel specimen with an array of Q-switched Nd:YAG laser-generated line sources and the measurement of laser-generated ultrasonic waves are performed on the specimen surface using the surface-mounting fiber optic Sagnac sensor. The surface-bonded fiber optic sensor developed in this study has a simple configuration for detection of ultrasonic waves. Effectiveness of surface-bonded fiber optic Sagnac sensors for remote sensing of ultrasound and in situ monitoring of structures is investigated. The capability of multi-point detection of ultrasound by this Sagnac sensor is also discussed.     

Fiber optic acoustic emission sensor and its applications in the structural health monitoring of CFRP materials

A fiber optic acoustic emission sensor based on fused-tapered coupler and its applications in structural health monitoring are proposed in this paper. The fiber optic acoustic emission sensor (FOAES) was tested using pencil lead break tests compared with the commercial acoustic emission sensor (R15 PZT). Besides, the sensor was embedded into the carbon fiber reinforced plastics (CFRP) materials and tested in the same way. It successfully detected the AE signals. FOAES was applied in the structural health monitoring (SHM) of CFRP materials. Damages of carbon fiber/epoxy composite laminates during three-point-bending test were monitored by surface-mounted and embedded FOAES, respectively. Results identified that the sensor embedded into composite structures could monitor damage of composite laminates on-line as the surface-mounted sensor did.     

基于M-Z干涉仪原理的光纤超声检测

提出了一种基于M_Z(Mach_Zehnder)干涉仪原理的光纤超声检测技术和U形结构的光纤传感器。讨论了光纤传感器与超声波之间的相互作用关系。对传感器的灵敏度与传感光纤的有效长度、U形结构的个数之间的关系进行了理论分析,实验结果和理论分析结果是一致的。通过比较超声波在三种不同入射方式下探测器的输出电压可知,该结构的光纤传感器在声信号垂直入射时由探测器探测到的信号最强,即传感器有很强的方向性,适合于对声表面波的定向检测。     

Optical fiber sensor-based detection of partial discharges in power transformers

In this paper, a fiber optic acoustic sensor system is designed and tested for on-line detection of the partial discharges inside high voltage power transformers. The fiber optic sensor uses a silica diaphragm and a single mode optical fiber encapsulated in a silica glass tube to form an extrinsic Fabry–Perot interferometer. Test results indicate that the developed fiber optic sensors are capable of detecting the acoustic signals propagating inside the transformer oil with high resolution and high frequency.     

基于光纤耦合器的声发射传感器

为检测变压器内局部放电产生的声发射信号,介绍了一种基于特殊光纤熔融拉锥耦合器型声发射传感器。它是利用声波引起的扰动改变耦合器两臂光功率输出的特点来检测声发射信号。实验结果表明：此种传感器在10kHz～250kHz范围内对声发射信号有良好响应,在155kHz灵敏度为5.6×10^-6V/Pa,噪声为1.8Pa声压,有望在复合材料与结构、电力无损检测方面得到应用。     

一种有源型光纤水听器原理与实验分析

分析了一种有源型光纤水听器的水声传感原理,在一段掺铒光纤中写入具有π相移的光纤光栅构成光纤激光器,水声压力作用在激光器上引起激光波长的移位,采用干涉法检测出波长移位引起的相位变化即得到声压的信息.水声探测实验表明,有源型光纤水听器的声压灵敏度为-166.5 dB(参考值1 rad/μPa).将不同工作波长的四元光纤水听器串接于一根光纤内组成水听器阵列,使用带通波分复用器将阵列发出的激光分离至各独立通道后检测出相应的声压信号,测得水听器之间的级串扰小于-60 dB,且单元水听器水声响应的动态范围不受影响.     

Water wave frequency detection by optical fiber sensor

An optical fiber sensor has been developed and applied to measure frequency of water waves based on wave induced polarization change of the light. The fiber sensor can accurately detect water wave frequency for regular and irregular waves. The optimum sag of sensing fiber to the sensor output’s linearity has been studied. The agreement of the fiber sensor and wave gauge in frequency and time domain suggests that the fiber sensor has great potential for passive acoustic sensing and wave monitoring.     

Fiber Sensing of Micro -Crack

Optical fiber sensors are used for sensing micro -cracking in composite and metal materials in aerospace applications.The sensing mechanism is based on the detection of acoustic emission signals, which are known to emanate from micro-cracks when they grow under further loading. The sensor head consists of a fiber Bragg grating that is capable of detecting acoustic emission signals generated by pencil lead breaking, of frequencies up to 200 kHz.     

Spatial characterization of the response of a silica optical fiber to wideband ultrasound

Optical fibers have long been recognized as a promising technology for remote sensing of ultrasound. Nonetheless, very little is known about the characteristics of their spatial response, which is significantly affected by the strong acoustic mismatches between the fiber and surrounding medium. In this Letter, a new method is demonstrated for wideband spatial acoustic characterization of optical fibers. The method is based on the excitation of a point-like acoustic source via the opto-acoustic effect, while a miniature fiber sensor is implemented by a π-phase-shifted fiber Bragg grating. Despite the relative complexity of acoustic wave propagation in the fiber, its spatial sensitivity in the high frequency band (6-30?MHz) exhibited an orderly pattern, which can be described by a simple model. This property reveals new possibilities for high-performance imaging using fiber-based ultrasound sensors, where knowledge of the sensor's spatial sensitivity map is generally required.