基于光纤声发射传感技术的桥梁监测实验研究

光纤传感器耐久性好,体积小,质量轻,易于实现分布式检测,能满足桥梁等土木结构的实时健康监测.该文设计了一非本征光纤法布里-珀罗(F-P)传感器结构,分析了光纤F-P声发射传感机理,建立了基于光纤F-P声发射传感技术的检测系统,用于混凝土桥梁健康状况的实时在线检测.实验结果表明,该传感器结构简单,体积小,成本低,制作容易,能有效用于桥梁健康监测,易于实现商品化.     

基于菲涅耳反射的准分布式光纤温度传感器

基于菲涅耳反射原理和光时域反射(OTDR)技术,提出了一种新型的、结构简单的准分布式光纤温度传感器.传感器由两个端面抛光的光纤对接构成,并在两端面间隙中填充温敏材料.传感器周围温度变化改变温敏材料的折射率,从而引起菲涅耳反射强度的变化.将三个传感头串联,利用OTDR探测各传感器菲涅耳反射的微弱变化实现温度传感和传感器定位.在-30～80℃范围内,随着温度升高,该系统各个传感头的菲涅耳反射强度单调增大,且温度传感特性具有良好的重复性,同时具有极低的附加损耗.     

基于保偏光纤模式干涉的温度传感技术

基于Sagnac光纤干涉仪偏振非互易的光纤温度传感器的理论、方案和相关技术,利用光强度直接测量的信号检测技术,实现了单点温度传感并进行了实验验证.实验和测试表明:这种温度传感器达到了0.01℃的温度分辨率和稳定性,通过改变温度传感头的长度和传感保偏光纤的双折射率,可方便地调节其测量范围.同时又提出了一种新的反射型保偏光纤温度传感方案并研制出微小型保偏光纤温度传感头.在此基础上,实现了多点温度测量,研制出大型变压器绕组温度监控用多点温度传感系统,在0～200 ℃的温度范围内达到了0.5℃的测量精度和分辨率,研制的传感头满足高电压绝缘和热油、热蒸汽的恶劣环境要求.     

基于波分复用的光纤多防区周界传感系统

提出了一种新的光纤多防区周界传感系统,采用波分复用技术实现了监控防区和通道的扩展。该系统对传统采用单根传感光纤和反射镜的结构作了改进,并扩展了传感光纤的数量,将多根传感光纤分别置于监控领域内的不同防区,每个防区分别用不同中心波长的光纤布拉格光栅作为反射装置,使每根传感光纤工作在不同的波长。利用波分复用器件与技术,多根传感光纤共用一套干涉系统,实现了多个干涉子系统同时、独立的监测。实验结果表明,该系统可以实现多个分散防区同时、独立的入侵检测和定位,信号响应时间小于1ms,不同防区间信号的串扰小于-20dB。     

小波分析在恶劣环境光纤传感中的应用(英文)

光纤光栅是通过外界物理参量对光纤布拉格波长的调制来获取传感信息的,是一种波长调制型光纤传感器。现代光纤传感系统的应用领域要求光纤传感器能适用于各种极端恶劣复杂环境,并在恶劣环境中实现高精度高灵敏度的检测。现有很多方法可用于光纤光栅的波长检测,但这些方法的精度都受限于不同的光噪声。如果光纤光栅检测系统的光源采用激光光源,信号功率可大大增强,但多余反射会产生有害干扰信号,限制光栅的波长解调精度。论文采用理论仿真和实验验证的方式将小波分析用于恶劣环境中的光纤传感信号的去噪。仿真和实验结果表明,小波分析处理方法可有效降低系统检测误差,提高测量精度和系统信噪比,满足恶劣环境中光纤传感检测的性能要求。     

基于FBG传感网络和时间反转聚焦成像方法的声发射定位技术研究

针对传统声发射定位系统存在的结构复杂、难以组网、定位精度低等问题,设计了一种基于光纤布拉格光栅(FBG)传感器网络和时间反转聚焦成像的声发射定位方法。在对时间反转聚焦定位原理分析的基础上,利用四个FBG传感器构建四点定位系统,并采用窄带激光边缘滤波技术实现信号解调。利用Morlet小波提取信号中特定频率成分,并计算模值和时差。通过建立时间反转聚焦模型实现声发射源定位,并在铝合金板结构上对整套成像定位方法进行验证。实验结果表明,该方法能有效地对400mm×400mm监测区域进行声发射定位成像,定位误差小于20mm,耗时小于2s。为声发射检测和定位提供了一种新的方法。     

一种新型光纤光栅传感器解调系统

选择线性滤波法解调光纤光栅(FBG)传感信号,实现传感光栅Bragg波长微小偏移的实时检测.利用单片机取代PC机,有效实现了系统的小型化.采用锁相放大电路和24位∑-Δ高精度A/D转换模块采集有用信号,提高系统精度和动态范围.使用USB接口模块存储和传输数据,使解调系统特别适合现场测量和野外作业的要求.设计出了一种新型FBG传感器解调系统,通过实验和数据验证了该系统高精度、便携带的特点.     

光学电流传感器系统方案和工作原理

根据光学电流传感器系统中传感头结构及传感机理对其进行分类,详细介绍了全光纤型、块状玻璃型、混合型光纤电流传感器及光纤光栅型电流传感器的传感原理及研究现状,并对它们的优缺点进行比较分析.最后对光学电流传感器的未来研究前景进行展望.     

光纤传感技术的发展及应用

介绍了传光型光纤传感器与传感型光纤传感器的基本原理,阐述了强度调制型光纤传感器、干涉型光纤传感器、光纤光栅以及光纤声发射传感器的应用,提出了我国光纤传感技术存在的问题以及发展方向.     

光纤传感器的研究及应用

介绍了光纤传感器与其他传感器相比的优点,还介绍了传感型光纤传感器与传光型光纤传感器的基本原理.同时,文章阐述了强度调制型光纤传感器、干涉型光纤传感器、光纤光栅和光纤声发射传感器的应用.文章最后提出了我国光纤传感技术存在的问题以及发展方向.     

用于局部放电探测的超声光纤传感方法

局部放电是一种有效的高压部件绝缘性能检测方法,可通过声、光及电等信号的探测来有效预报绝缘劣化程度。该文建立了基于局部放电超声信号检测的光纤传感器测试系统,使用Mach-zehnder光干涉法来检测声信号导致的光程差,测算测量回路的微小机械形变。实际测试结果表明,该系统具有高的测试灵敏度,可精确测量纳米级的机械形变,准确反映局部放电过程引起的超声信号。采用该光纤传感系统可对多层陶瓷器件的局部放电进行跟踪测量。     

Fiber optic sensors focus on smart systems

Materials with structurally integrated fiber-optic sensors, the first step toward smart structures, which continuously monitor their own vibration, internal strain and deformation, temperature, and structural integrity are described. It is shown that the Fabry-Perot fiber-optic strain sensor has capabilities that far exceed those of conventional foil strain gauges, which holds the promise of responding to acoustic emission signals while simultaneously tracking the high loads likely to be encountered in practical structures such as aircraft wings. The same sensing system may be able to monitor the degree of cure during fabrication of thermoset composite structures. The fabrication and characterization of such all-fiber, intrinsic Fabry-Perot strain sensors are discussed. Passive and active homodyne signal recovery techniques used in the fiber-optic sensor systems are also described     

Combined optical fiber interferometric sensors for the detection of acoustic emission

A type of combined optical fiber interferometric acoustic emission sensor is proposed. The sensor can be independent on the laser source and make light interference by matching the lengths of two arms, so it can be used to monitor the health of large structure. Theoretical analyses indicate that the system can be equivalent to the Michelson interferometer with two optical fiber loop reflectors, and its sensitivity has been remarkably increased because of the decrease of the losses of light energy. PZT is powered by DC regulator to control the operating point of the system, so the system can accurately detect feeble vibration which is generated by ultrasonic waves propagating on the surface of solid. The amplitude and the fre- quency of feeble vibration signal are obtained by detecting the output light intensity of interferometer and using Fourier transform technique. The results indicate that the system can be used to detect the acoustic emission signals by the fre-quency characteristics.     

基于Fabry-Perot光纤应变传感技术的监测系统

介绍了外腔式光纤法布里-珀罗(F-P)应变传感器的基本原理和信号调理技术。设计了基于F-P应变传感技术和虚拟仪器技术的结构应变实时监测系统并应用于桥梁健康监测现场。现场应用结果表明,法布里-珀罗光纤传感器与传统传感器相比具有响应速度快、动静态测量、绝对测量、抗电磁干扰和易于与钢筋、混凝土复合等特点,适用于桥梁等结构的应变测试。所设计的应变监测系统可用于结构健康状态的在线监测。     

光纤F—P和FBG传感器通用解调系统的研究

针对目前不同种类传感器在建筑结构及其工作环境进行实时监测应用上的实际情况,提出了一种利用可调F—P滤波器对光纤法珀传感器和光纤布拉格光栅传感器通用解调方案,研究了解调系统的组成和对传感器的解调原理．初步实验结果表明,系统能够对上述2种传感器进行解调,并具有复用能力,光纤法珀传感器的应变解调精度在2με以下,光纤布拉格光栅传感器解调精度在0．5με以下,是一种低成本、通用的解调系统．     

微弱光纤声发射信号检测电路建模与仿真

采用双波长稳定技术可克服光纤声发射传感器正交工作点偏移产生的信号衰减与失真,但会造成输出光微弱而难以检测。针对该问题,给出一种光纤声发射信号检测电路设计方案,建立了光电管、前置运放、电流转换的子模型及系统模型,分析了系统噪声特性与稳定性,并采用通用电路模拟软件PSPICE进行仿真验证,仿真实验结果表明,采用该设计方案能有效展宽频带和提高信噪比,可用于频带宽度为318 kHz与幅值低达1 nA的光电流检测。     

A study on the development of transmission-type extrinsicFabry-Perot interferometric optical fiber sensor

The conventional reflection-type extrinsic Fabry-Perot interferometric (EFPI) optical fiber sensor has good sensitivity and resolution compared with other types of optical fiber sensors. However, they have the disadvantage that the distinction of strain direction of EFPI is difficult because of measurement method by only fringe counting. This paper presents the newly developed transmission-type EFPI (TEFPI) optical fiber sensor, which has been improved by additional functions, and whose measuring system differs from that of the reflection-type EFPI optical fiber sensors using a single-mode fiber (SMF) and multimode (MMF) fibers as light guides and reflectors, respectively. The output signal of the TEFPI optical fiber sensor was analyzed with the uniform plane wave-based model, the SMF power distribution-based model and the splice loss-based model; the analyzed signals were then verified experimentally. Based on the results of analysis, the TEFPI optical fiber sensor was fabricated using two single-mode fibers connected to the light source and optical receiver; this was then used in strain measurement. The strain measured by the TEFPI optical fiber sensor was compared with that measured by the electric strain gauge     

偏振正交双频DBR腐蚀声发射传感器研究

为了实现基于光纤传感器的金属腐蚀在线监测,以金属Q235腐蚀声发射在线监测为目标,采用分布式布喇格反射（DBR）光纤激光器作为腐蚀声发射传感器的方法,通过对偏振正交DBR光纤激光器的工作机理及模型进行研究,分析了偏振正交双频DBR激光器用于腐蚀声发射传感器的谐振腔参量对其性能影响的规律,并进行了基于偏振正交双频DBR激光器的声发射检测实验,实现了偏振正交DBR光纤激光器的优化设计,提出了表征Q235碳钢腐蚀阶段的特征量。结果表明,偏振正交DBR光纤激光器不仅能实现对金属腐蚀声信号的检测,其检测频带范围为0MHz~1MHz,还能实现通过平均拍频值的变化来表征金属腐蚀主要的3个腐蚀阶段。该研究为偏振正交DBR腐蚀声发射传感器及组网的优化设计与制作提供了理论和技术基础,对金属腐蚀特别是核级关键材料的在线腐蚀监测具有重要意义。     

Self-calibrated interferometric-intensity-based optical fibersensors

This paper presents self-calibrated interferometric-intensity-based optical fiber sensors, which combine for the first time fiber interferometry and intensity-based devices into a single sensor system. The sensor involves an extrinsic Fabry-Perot (FP) interferometric cavity. The broadband light returned from the FP cavity is split into two channels in such a way that one channel has a coherence length much longer than the doubled air-gap separation in the sensor so the FP generates effective interference, while the coherence length in the other channel is so short that no effective interference takes place. As a result, the optical signal in the channel with a long coherence length yields information about the FP cavity length while the signal in the other channel is proportional only to the source power, fiber attenuation, and other optical loss factors in the optical path. To eliminate fringe direction ambiguity and relative measurement limitations associated with interferometric sensors, the sensor is designed such that it is operated over the linear range between a valley and a peak of one interference fringe in the first channel. Moreover, the ratiometric signal-processing method is applied for the signals in the two channels to obtain self-calibrating measurement to compensate for all unwanted factors, including source power variations and fiber bending losses. Various pressure and temperature sensors based on the self-calibrated interferometric/intensity-based scheme are designed, fabricated, and tested. Experimental results show that a resolution as high as 0.02% of full scale can be obtained for both the pressure and temperature measurements     

Planar location of the simulative acoustic source based on fiber optic sensor array

A fiber optic sensor array which is structured by four Sagnac fiber optic sensors is proposed to detect and locate a simulative source of acoustic emission (AE). The sensing loops of Sagnac interferometer (SI) are regarded as point sensors as their small size. Based on the derived output light intensity expression of SI, the optimum work condition of the Sagnac fiber optic sensor is discussed through the simulation of MATLAB. Four sensors are respectively placed on a steel plate to structure the sensor array and the location algorithms are expatiated. When an impact is generated by an artificial AE source at any position of the plate, the AE signal will be detected by four sensors at different times. With the help of a single chip microcomputer (SCM) which can calculate the position of the AE source and display it on LED, we have implemented an intelligent detection and location.