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1、摘要摘要 光纤光栅(fiber Bragg grating，FBG)是近几年发展最为迅速的光纤无源器件之一。光纤光栅作为传感元件具有其它传感器无可比拟的优点。FBG传感器结构紧凑，易于集成和埋覆测量，对传感信息采用本征性波长编码，免受电磁噪声和光强波动的干扰，并且便于采用复用(波分、时分、空分)技术实现对多种传感量(应力、温度等)的准分布式多点测量，在民用、航空、船舶、电力和石油等领域的安全监测方面有着广泛的应用前景。目前，FBG传感解调的方法和装置包括非平衡马赫一曾德干涉仪法、边缘滤波器法、匹配FBG滤波器法和可调谐法布里一珀罗(FabryPerot，F-P)滤波器法等。其中，可调谐F-P滤
2、波器法通过微驱动器调谐腔长扫描传感FBG，具有灵敏度高、调谐范围大等优点更适用于多点扫描。因此本文对可调谐F-P滤波器解调方法进行了较为深入的研究。本文研究了端面光吸收损耗，有限多光束干涉及反射平板不平行对F-P滤波器光学性能的影响，提出了可调谐F-P滤波器的参数范围和设计要求。通过仿真实验设计了基于磁场梯度力的微位移驱动器和基于电场力的微位移驱动器。分析了基于超磁致伸缩材料(giant magnetostrictive material，GMM)和基于压电陶瓷(piezoelectric，PZT)微位移驱动技术的特点，确定了微位移驱动方案。设计了一种可调谐F-P滤波器结构，利用该结构能够实现
3、对FBG传感器的解调功能。为了消除可调谐F-P滤波器腔长随温度漂移的影响，降低系统复杂性，通过有限元方法对可调谐F-P滤波器结构的温度稳定性进行了研究。首先通过实验测得可调谐F-P滤波器结构的温度一腔长变化曲线，与有限元分析软件仿真得到的温度一腔长变化曲线对比确定了有限元模型和有限元计算方法的可行性，然后建立了基于复合结构(因瓦合金、碳钢)的低温度漂移有限元模型，应用低热膨胀系数的因瓦合金补偿了PZT模块的热膨胀差异。仿真研究表明，复合结构消除了温度漂移现象。为了准确测定解调系统输出信号的峰值发生时间，需要滤除噪声，恢复输出信号，因此对信号重建算法进行了研究。通过对系统输出信号的频谱分析，确定
4、了噪声的频率范围，设计了基于凯泽窗的数字低通滤波器。针对低I通滤波后依然存在噪声导致信号失真的问题，根据FBG的反射谱特性对信号进行了局部高斯拟合，保证了求取峰值时间的准确性。 分析了串联型和并联型的实时校正方案，选择并完善了并联型方案。最后设计了一种基于可调谐F-P滤波器的多点FBG解调系统，此系统根据48个参考点采用快速分段算法确定PZT驱动电压一波长函数，使用此函数实时校正微驱动器件的非线性误差以及可调谐F-P滤波器的结构性误差，从而能够提高系统的测量精度。此外，设计了以现场可编程门阵列(field programmable gatearray，FPGA)为核心的后续电路单元，将解调系统
5、的控制、滤波计算和数据压缩等电路集成在FPGA芯片内部，保证了系统的实时性。关键词法布里一珀罗滤波器；光纤光栅传感器；解调；数字信号处理摘要Abstract Fiber Bragg gratings are one type of developing fast passive fiber devices inrecent yearsAs sensing element，they encode the sensing information in awavelength form，which are their distinguished advantages over other trans
6、ducersFBG sensors have the characteristics of compact structure，easy to integrate and buryAlso they are modulated by wavelength and immune to electromagnetic interference and light intensity fluctuationMulti-sensing like stress and temperature sensing are achieved by wavelength，time and space divisi
7、on multiplexing technologiesFBG sensors are mainly applied in the fields of civilian，aviation，ship，electric power and petroleumMany demodulationtechniques and methods for FBG sensors have been reported such as the fiber unbalanced Mach-Zehnder interferometer，edge filters，and matched fibre gratings f
8、ilters and tunable fiber Fabry-Perot(F-P)interferomcterDue to theadvantages of high sensitivity,wide tunable range，the fiber F-P interferometerdemodulation uses micro-driving device to change the microcavity for scanningspectrum of the FBGs，which is more sutable for multi-point demodulatingTherefore
9、，a FBG demodulation method based on the tunable fiber F-Pinterferometer is deeply studied Absorption loss in the fiber interfaces，effects of the finite multi-beam interference and the unparalleled reflection plates on the F-P interferometer performance are given hereThen the parameters and design re
10、quirements of thetunable F-P interferometer are presentedA driver based on gradient magneticfield force and a driver based on electric field force are designed by simulationexperimentsThe micro-displacement driver is designed on the base of analyzingthe features of giant magnetostrictiVe material(GM
11、M)and piezoelectric(PZT)Micro-displacement driversIn this thesis，a tunable F-P interferometer structure is designed to demodulate FBG sensorsAim at keeping the temperature stability of the F-P microcavity length and decreasing the system complexity,an F-P interferometer structure with low temperatur
12、e drift is studied by using theANSYS softwareFirstly,according to the experiments，the temperature-lengthcurve of the F-P microcavity is builtThe feasibility and correctness of the finiteelement modeling simulation are verified by contrasting the experiments and simulation curvesThen a new structure
13、of low temperature drift F-P interferometer is designed by using the composite materials(Invar alloy and carbon steel)，which compensate the thermal expansion differences of the PZTmoduleSimulating results show that the composite structures eliminate the temperature drifts In order to get the accurat
14、e time of the output signal peak of the demodulation system，signal reconstracting arithmetics are presented to filter the noisesBy analyzing the frequency spectrum of the output signal，we get the frequency range of noises and design a low-pass digital filter using Kaiser windowBecause the low-pass d
15、igital filter cant filter the noise completely,localGaussian fitting filter is designed according to the spectral reflective characteristics of FBG. Series and parallel correction methods are analyzed，and we choose and imprvove the parallel one.A multi-point FBG sensor demodulation system based on t
16、he tunable F-P interferometer is built.The PZT driving voltage-wavelength function is built according to the 48 reference points using fast methodThis system can calibrate the nonlinear problems of the micro-displacement driver and the structural errors of tunable F-P interferometer in real-time,that is to say，the measurement precision is improved.Furthermore,circuits by using field progr
