用于周界安防的光纤光栅振动传感系统研究

基于光纤光栅传感理论设计了一种应用于周界安防的低频振动传感器.采用商用解调仪OPD4000对传感器的灵敏度进行了测试,在10～100 Hz频率范围内,传感器灵敏度高于1 000 pm/g.基于非平衡迈克尔逊干涉仪相位载波调制(PGC)解调技术搭建了一套光栅传感器解调系统,实现对传感器低频振动信号的高精度实时解调,使得该系统可广泛应用于机场、监狱、油库、核场所等重要区域的周界安防中.     

基于FP-LD强反馈的光纤迈克尔逊干涉仪传感系统

针对采用传统自组光纤激光器的光纤传感系统存在成本较高和结构复杂等问题,提出了一种基于商用激光器强反馈的光纤迈克尔逊干涉仪(FMI)传感解调系统。该系统采用商用法布里-珀罗腔型半导体激光器(FP-LD)为光源,由直流电源直接驱动,经FMI的反射、干涉后对其形成强反馈;利用多纵模激光拍频解调技术实现对FMI的传感解调,将FMI光域干涉光强的变化直接转化为电域拍频包络的变化。研究了不同FMI臂长差时拍频信号随温度的变化过程及传感系统灵敏度。实验结果表明:当臂长差分别为0.45、0.40 m时,灵敏度分别为325、358.33 kHz/℃。     

采用后向瑞利散射空间差分的周界安防分布式振动监测

提出了应用于周界安防的基于后向瑞利散射光空间差分干涉的光纤分布式振动传感监测方案。环境振动信号引起传感光纤的相位变化,含有相位信息的后向瑞利散射信号注入到非平衡迈克尔逊干涉仪,实现了后向瑞利散射信号的空间差分干涉,光纤分布式振动传感监测完成相位信号的解调,提高了系统的灵敏度。该系统能够实时监测入侵者的行走路线和速率以及模拟挖掘的距离的判断,实现了15 dB的信噪比以及35 m的探测距离。     

基于Sagnac干涉仪的多点局部放电检测系统

提出了一种基于光纤Sagnac干涉仪用于多点局部放电超声检测的光纤传感系统。该超声检测系统由光源、单模光纤延迟线、光纤耦合器、相位调制器、偏振控制器和对比度为1的光纤Sagnac干涉仪组成。首先介绍了传感系统的超声检测的原理,然后搭建了模拟局部放电超声实验平台,利用Nd∶YAG激光器照射钢板激发出的表面波和高频声源,针对局部放电超声在钢板和变压绝缘油中的传播情况进行了实验。实验结果证明了使用该系统用于局部放电超声检测的有效性,在100kHz～200kHz频率范围内,信噪比可达40dB以上,同时实验验证了该Sagnac传感器对局部放电超声的多点检测能力。该光纤超声检测系统结构简单,频率响应高,成本低廉在局部放电等领域有着巨大潜力。     

基于光纤激光器的微振动信号保真拾取干涉仪

提出了一种新型的远距离微振动信号的测量和保真拾取系统.该系统基于迈克尔逊干涉仪结构,以窄线宽光纤激光器为光源,采用相位载波零差解调方案实现信号的还原.通过优化压电陶瓷堆(PZT)相位调制器驱动电路,有效地提升了系统的频率响应范围.通过引入移相电路提高了系统的信噪比.系统在50 Hz～4 kHz频率范围内线性度良好,输出信号的信噪比为60 dB,谐波抑制比为50 dB,系统的灵敏度为1×10-5rad/Hz1/2.     

1阶反馈稳定光纤3×3耦合器干涉测量系统

为了消除环境干扰对光纤干涉测量系统的影响,采用光纤3×3耦合器和光纤光栅构成光路复合在一起的两个光纤迈克尔逊干涉仪构成了光纤干涉测量系统。利用光纤光栅作为反射镜,两个光纤迈克尔逊干涉仪共有几乎相同的光路。其中一个光纤迈克尔逊干涉仪通过一个1阶反馈来补偿环境干扰的影响,实现对该测量系统的稳定;另一个光纤迈克尔逊干涉仪用于完成测量工作。结果表明,1阶反馈可以对0Hz～21Hz的干扰进行补偿,使得该测量系统适合于在线精密测量。     

1阶反馈稳定光纤3×3耦合器干涉测量系统

为了消除环境干扰对光纤干涉测量系统的影响,采用光纤3×3耦合器和光纤光栅构成光路复合在一起的两个光纤迈克尔逊干涉仪构成了光纤干涉测量系统.利用光纤光栅作为反射镜,两个光纤迈克尔逊干涉仪共有几乎相同的光路.其中一个光纤迈克尔逊干涉仪通过一个1阶反馈来补偿环境干扰的影响,实现对该测量系统的稳定;另一个光纤迈克尔逊干涉仪用于完成测量工作.结果表明,1阶反馈可以对0Hz～21Hz的干扰进行补偿,使得该测量系统适合于在线精密测量.     

新型簧片式光纤加速度传感器研究

研制了一种新型光纤加速度传感器。基于迈克尔逊干涉仪原理,采用了质量块和可 弯曲簧片结构,通过使用竖直 绕制传感光纤和横向绕制参考光纤的方式提高了加速度传感器的加速度灵敏度。实验测试了 其加速度灵敏度以及横向串扰。在簧片厚为1mm、质量块质量为208 g时,其加速度灵敏度 可达556rad/g(g为重力加速度);在噪声本底为10－4 rad/Hz 、加速度传感器工作频率为100Hz时,其可探测的最小加速度信号为 200ng/Hz(g为重力加速度)。采用该全金属结 构,传感器可更好地用于微弱信号检测。     

激光干涉条纹锁定系统测量地面低频振动谱

地面振动噪声是在地面高精度实验中一个重要的误差来源,安静环境下地面振动噪声水平的幅度为纳米量级,通常干涉仪无法直接测量.设计并制作用于了纳米精度测量的激光干涉仪反馈控制系统,该系统由激光器及稳频装置、干涉系统、检测及控制电路和位移反馈执行机(压电陶瓷)组成.采用一个长周期的折叠摆对水平方向0.3 Hz以下的振动频率进行...     

基于光纤环形激光器的传感技术研究与应用

基于光纤环形激光器的新一代光纤传感系统通过解调激光波长偏移来检测外界参量变化,得利于激光光谱窄线宽及高信噪比的特性,可实现高分辨率、高灵敏度、大动态范围的传感监测。文章介绍了包括基于光纤光栅、迈克尔逊干涉仪、法布里-珀罗腔、萨格奈克环以及马赫-曾德尔干涉仪等多种结构的光纤传感器工作原理,以及进一步构成光纤环形激光传感器的特性和多种应用案例,并对未来该领域的关键技术发展进行了分析。     

金属环封装低频光纤布拉格光栅振动传感系统研制

研制了一种金属环封装的单柱体芯轴式光纤布拉格光栅(FBG)振动传感器,搭建了基于非平衡迈克耳逊干涉仪相位载波调制(PGC)解调技术的FBG振动传感器解调系统,实现了低频振动信号的高精度实时解调,并分析了各参数对传感器谐振频率和灵敏度等特性的影响。实验结果表明,研制的FBG振动传感器谐振频率为388Hz,在10～200Hz频率范围内,传感器的加速度灵敏度约为81pm/g,且加速度响应平坦,起伏小于1dB,与理论分析结果基本一致。研制的振动传感器可实现200Hz以下低频振动信号的实时检测,解调系统的波长检测精度为1.07×10-3 pm,最小可检测加速度为1.3×10-5 g。     

Multi-Channel FIR HCN Laser Interferometer on HT-7 Tokamak

A Five-channel far-infrared (FIR) hydrogen cyanide (HCN) laser interferometer was developed to measure plasma electron density profile on the HT-7 superconducting tokamak. The structure of the five-channel FIR laser interferometer is described. The laser source used in the interferometer was a continuous wave glow discharge HCN laser with 3.4 m cavity length and 100 mW power output at 337 μm wavelength. The temporal resolution was 0.1 ms and the detection sensitivity was 1/12 fringe. Preliminary experimental results measured by the interferometer on HT-7 tokamak are reported.     

Distributed optical fiber perturbation sensing system based on Mach-Zehnder interferometer

A novel distributed optical fiber vibration-sensing system based on Mach-Zehnder interferometer has been designed and experimentally demonstrated. Firstly, the principle of Mach-Zehnder optical path interferometer technique is clarified. The output of the Mach-Zehnder interferometer is proportional to the phase shift induced by the perturbation. Secondly, the system consists of the laser diode (LD) as the light source, fiber, Mach-Zehnder optical interferometers as the sensing units, a 1×N star fiber-optic coupler, an N×1 fiber-optic coupler, a photodiode (PD) detector, and a computer used in signal processing. The entire monitoring region of this system is divided into several small zones, and each small monitoring zone is independent from each other. All of the small monitoring zones have their own sensing unit, which is defined by Mach-Zehnder optical interferometer. A series of sensing units are connected by the star fiber-optic couplers to form a whole sensing net. Thirdly, signal-processing techniques are subsequently used to calculate the phase shift to estimate whether intruders appear. The sensing system is able to locate the vibration signal simultaneously, includ-ing multiple vibrations at different positions, by employing the time-division multiplexed (TDM) technique. Finally, the operation performance of the proposed system is tested in the experiment lab with the conditions as follows: the number of the sensing units is 3, the length of the sensing fiber is 50 m, and the wavelength of the light diode is 1550nm. Based on these investigations, the fiber surrounding alert system is achieved. We have experimen-tally demonstrated that the sensing system can measure both the frequency and position of the vibration in real time, with a spatial positional resolution better than 50 m in an area of 1 km2.     

Laser interferometer using a dual interference method

A stabilised Michelson interferometer system using a new interference mode has been developed, in which a specially designed beam-splitter produces two complementary interference patterns. With differential detection, the laser intensity noise is efficiently eliminated, and the system is simpler and stabler. The measured displacement sensitivity is 10?2 A?/ ?(HZ).     

基于相位光时域反射的光纤分布式声波传感研究

文中提出了一种光纤分布式声波传感方案。作用在传感光纤上的声波信号导致后向瑞利散射光的相位变化,将含有声波信息的后向瑞利散射信号注入到迈克尔逊干涉仪,并采用相位载波解调算法解调出相位信息。实验中采用压电拉伸器模拟声波振动,分布式声波传感系统实现了10 m的空间分辨率以及平坦的频响。     

A Michelson interferometer with balanced detection for thecharacterization of modulation and noise properties of semiconductorlasers

A Michelson interferometer with balanced detection, built to study semiconductor lasers, is analyzed. The quantum noise due to vacuum fluctuations, coupling losses, detector quantum efficiency, and spatial mode mismatches are included in the analysis. The limits for frequency noise detection and the sensitivity of the interferometer are examined. It is observed that under ordinary measurement conditions the frequency noise can only be measured up to slightly above the cavity bandwidth of the laser. Comprehensive measurement procedures are proposed, and experimental results showing the frequency modulation response, measured from 10 kHz to 8 GHz, of a three-section distributed feedback (DFB) laser and the frequency noise spectra, measured from 30 MHz to 8 GHz, of a two-section distributed Bragg reflector (DBR) laser are presented. These results reveal new cavity detuning effects in the noise characteristics of tunable DBR lasers     

光纤干涉仪输入光偏振态反馈控制理论分析

具有较大非平衡长度的光纤Mach-Zehnder干涉仪解调DFB激光器传感信号时,存在着偏振衰落现象,为了解决这一问题,提出了一种对干涉仪输入光偏振态进行反馈控制的方案,论述了具有反馈控制功能的干涉仪信号解调系统,推导了反馈控制系统的控制信号与干涉仪条纹可见度之间的关系式,分析了该系统在不同光信号输入情况下的工作状况,从理论上证明了利用该系统可在一定条件下使干涉仪的条纹可见度稳定在1附近,论证了该方案消除干涉仪解调传感信号时偏振衰落现象的可行性。