光纤Michelson干涉仪系统的研究

文章介绍了光纤Michelson干涉仪系统的结构.阐述了光纤偏振控制器结构、工作原理以及其对光纤Michelson干涉仪系统传感臂偏振态的控制.同时,给出了光纤Michelson干涉仪系统中信号光与参考光的干涉原理以及影响干涉光强的因素.最后,文章介绍了光纤Michelson干涉仪系统的应用.     

基于Michelson干涉仪的光纤AE传感器的研究

文章介绍了光纤传感器的应用和S状光纤声发射(Acoustic Emission,AE)传感器的结构,给出了此类光纤AE传感器与超声波之间的相互作用,以及基于光纤Michelson干涉仪的此类光纤AE传感器灵敏度的理论分析,最后得到的灵敏度理论分析结论与MATLAB模拟结果相一致.     

光纤Michelson干涉仪干涉条纹对比度的研究

通过实验测定了光纤Michelson干涉仪输出的干涉信号,并由此计算了干涉条纹对比度.从条纹对比度的拟合曲线出发,分析了可能影响光纤干涉仪干涉信号对比度的主要因素,为实验中条纹对比度的进一步提高提供有益的参考.     

基于Michelson 干涉仪的光纤分布式扰动传感器

提出并研究了基于Michelson 干涉仪的应用于检测时变扰动的光纤分布式传感器。所提出的光纤传感器由两个Michelson 干涉仪和一个光纤延迟环组成。扰动作用在传感光纤上,引起传输光波相位的调制作用,可以通过该传感器进行检测并得到扰动的位置信息。通过光电探测器对干涉信号进行接收。对接收到的信号进行隔直,并通过求取峰峰值的方法对隔直后的信号进行预处理。通过希尔伯特变换、相位去包裹和三角函数运算可以提取出预处理信号中包含的相位信息。最后,通过频谱分析和相应的数学运算可以实现扰动的定位。在20 km 的监测距离内通过实验验证了传感器的可行性。所提出的光纤传感器具有实时性好、抗偏振性、低成本的独特优势。     

Mach－Zehnder光纤干涉仪可见度分析

基于部分相干理论，导出高斯谱光源谱线宽度与干涉可见度的关系，为干涉型光纤传感器的系统设计提供了理论依据，并借助计算机绘制出干涉仪可见度与由于干涉仪两臂不平衡而引起传播时间差的关系曲线。     

基于法拉第旋转镜的Michelson干涉仪偏振相位噪声研究

在理论上研究了由法拉第旋转镜构成的Michelson干涉仪的偏振特性,推导出Michelson干涉仪的偏振引入相位噪声与法拉第旋转镜旋转角偏差的关系式.理论分析法拉第旋转角有偏差时,引导光纤中的偏振态扰动(偏振噪声)会在干涉仪中引入相位噪声,该相位噪声水平与引导光纤中的偏振噪声水平和干涉仪输入光的偏振态有关.并且当法拉第旋转角偏差±2°时,可估算偏振引入的相位噪声与引导光纤中偏振噪声的幅度比值低于2×10-3;在多波长复用系统中,若法拉第旋转角偏差±5°,该幅度比值仍低于1.5×10-2.实验中观察到该幅度比值低于2.5×10-2,并发现输入光偏振态变化并不引起干涉仪相位噪声的变化,由此可知由法拉第旋转角偏差引入的相位噪声符合理论估算的量级,得到了很好的抑制.     

波长解调用偏振无关光纤干涉仪的研究

针对光纤激光传感器信号解调过程中,干涉仪输出干涉条纹可见度受输入光偏振态变化以及两臂单模光纤双折射效应的影响,介绍了一种简单的光纤干涉仪消除偏振衰落技术,通过在Michelson光纤干涉仪上加两个法拉第旋转镜来提高输出条纹可见度。使用琼斯矩阵法对干涉仪系统进行理论计算,证明法拉第旋转镜旋转角度在理想的45°附近时能达到很好的消偏振效果,并通过实验进行了有效地论证。     

偏振态调制的偏振无关的干涉型光纤传感器

针对低双折射光纤双束干涉型传感器两壁偏振态随机变化引起的信号衰落,提出了一种新型干涉型光纤传感器的消偏振衰落方案。通过在光纤干涉仪的任何一臂加对光波偏振态适当的高频调制,在输出端高频滤波后,可以消除仪两壁偏振态的随机变化的影响,获得干涉信号可见度为0.707的稳定输出,从而实现干涉型光纤传感器的消偏振衰落。     

光纤Michelson干涉仪型折射率和温度同时测量传感器

基于Michelson干涉仪原理,制作了一种可同时测量折射率和温度的全光纤传感器。传感器由单模光纤和一段长度为5mm的细芯光纤错位熔接而成。对该传感器的折射率和温度响应特性进行理论分析,并在折射率和温度的变化范围分别为1.333 3~1.404 9和20~90℃的环境中对传感器的响应特性进行实验研究,结果表明,随着环境折射率的变化,该传感器输出光谱峰值功率的响应灵敏度为-41.10dB/RIU,而光谱峰值波长对折射率变化不敏感;随着环境温度的变化,该传感器输出光谱峰值波长的响应灵敏度为23.15pm/℃,而光谱峰值功率对温度变化不敏感。因此,通过同时监测传感器输出光谱的功率变化和波长漂移量,可实现折射率和温度的同时测量。该传感器制作简单,测量精度高,在生物医学领域有较好的应用前景。     

输入光偏振态对光纤干涉仪条纹可见度的影响

文章分析了输入光偏振态对光纤Mach2Zehnder干涉仪条纹可见度和相位的影响,并通过实验进行验证。实验中,在干涉仪一干涉臂加入PZT相位调制器,通过示波器直接观测输入光偏振态对干涉仪输出光强波形的影响,并对输出波形变化进行了理论分析,验证了输入光偏振态对干涉仪可见度、相位的影响。     

System design and optimization of optically amplified WDM-TDMhybrid polarization-insensitive fiber-optic Michelson interferometricsensor

We investigate the optically amplified time-division-multiplexed (TDM) polarization-insensitive fiber-optic Michelson interferometric sensor (PIFOMIS) system using erbium-doped fiber amplifier (EDFA). The EDFA was named preamplifier, in-line amplifier or postamplifier; by the position it was located. We find that the preamplifier EDFA has limited usefulness because of its unstable amplification of the optical pulse trains. Both post- and in-line cases can work successfully in the TDM-PIFOMIS system. The amplitudes of the optical pulse trains are stable after amplified by the in-line EDFA, this is a significantly advantage of the optically amplified TDM-PIFOMIS system. The MPDS of the unamplified TDM-PIPOMIS system with an extinction ratio (ER) of 33 dB of the output pulse of the optical guide wave (OGW) modulator was 2.4×10^-5 rad/(Hz)^1/2 at 1 kHz. For maintaining MPDS better than 3.4×10^-5 rad/(Hz)^1/2 at 1 kHz, the allowable worst ER for the post- and in-line amplified system are 20 and 17.8 dB, respectively, and the corresponding input signal peak power should be larger than -20 and -25 dBm. While employing such two post- and two in-line EDFAs in the TDM-PIFOMIS system, the allowable loss of the sensor array is 47 dB. We analyze the phase-induced intensity noise (PIIN) of the optically amplified TDM-PIFOMIS system in detail and propose methods to reduce the PIIN. The output optical pulse of an intensity modulator with high ER is a key issue to minimize the PIIN and sensor crosstalk in the system. In order to reduce the system PIIN, complexity and cost, we suggest an optimum optically amplified WDM (wavelength-division multiplexing)-TDM hybrid PIFOMIS system with four wavelengths and four eight-sensor subarrays     

Thermal phase compensation in fiber-optic interferometers

A method to hold an interferometer in quadrature by thermal phase tracking is described. The phase tracker has an extremely large tracking range (>10^{4}rad) such that the interferometer may be locked to zero path-length difference. The advantages and operation of this scheme to fiber-optic interferometry are described.     

Zero path-length difference in fiber-optic interferometers

Techniques to measure and achieve very small path differences in fiber interferometers are described. The noise properties of the small path difference interferometers are briefly described.     

Optical displacement measurement with GaAs/AlGaAs-basedmonolithically integrated Michelson interferometers

Two monolithically integrated optical displacement sensors fabricated in the GaAs/AlGaAs material system are reported. These single-chip microsystems are configured as Michelson interferometers and comprise a distributed Bragg reflector (DBR) laser, photodetectors, phase shifters, and waveguide couplers. While the use of a single Michelson interferometer allows measurement of displacement magnitude only, a double Michelson interferometer with two interferometer signals in phase quadrature also permits determination of movement direction. In addition, through the use of two 90° phase-shifted interferometer signals in the latter device, a phase interpolation of 2π/20 is possible, leading to a displacement resolution in the range of 20 nm. The integration of these complex optical functions could be realized with a relatively simple fabrication process     

Elimination of coherent Rayleigh backscatter induced noise in fibre Michelson interferometers

A technique for the elimination of coherent Rayleigh backscatter effects in fibre optic Michelson interferometers is demonstrated. This technique allows interferometers to be addressed over a significant length of fibre lead, without Rayleigh backscatter induced excess noise limitations.<>     

Multistable fiber-optic Michelson interferometer with electroopticfeedback exhibiting 95 stable states

The multistable behavior of a fiber-optic Michelson interferometer with electrooptic feedback using a piezoelectric phase modulator is investigated. A linear stability analysis of the third-order differential equation used to describe the system reveals the number of stable states increases with the ratio τ/T of the system time constant (τ) and the feedback delay time (T). In laboratory investigations 95 stable states were achieved with τ/T>50     

Development of fiber-optic depolarizer and its application tomeasurement systems for polarization-insensitive operation ofsilica-waveguide matrix switches

This paper describes an automatic system that measures the bias and switching currents of all the switch elements in the polarization-insensitive operation of silica-waveguide 8×8 matrix switches. A new type of depolarizer that can be used for coherent laser sources was compactly packaged with an excess loss of 6 dB. The packaged depolarizer was coupled to an automatic measurement system that was achieved mainly by using two 64-channel power supplies that drive all the heaters of a matrix switch via a computer. By using a DFB laser source at 1305 nm, whose output was unpolarized with the depolarizer, all the switch elements could be adjusted so that they were polarization insensitive within 0.3 dB to any polarization state. About 2 hours were required to complete the measurement for one matrix switch     

The design of fiber-optic filters

Fiber-optic filters can be used for processing wideband radio-frequency, microwave, and millimetric signals directly in the optical domain avoiding costly electrooptic and optoelectronic conversions. Because these filters sum signals on an intensity basis, they are bound to be positive and, hence, heavily restricted in their achievable performance. Nevertheless, such filters are the only choice because positivity is a consequence of the underlying physical mechanism. In this paper, the authors present a new design methodology to realize an arbitrary filter as a difference of two positive filters, thus overcoming any performance limitation