采用3×3耦合器的分布反馈式光纤激光传感器解调技术

摘要

The 3×3 coupler-based Michelson interference demodulation system was established to achieve a stable demodulation of distributed feedback optical fiber laser sensor (DFB FL) in a wide dynamic range.The symmetric demodulation algorithm (NPS) and arctangent demodulation algorithm used in this system were in-depth researched.Firstly,the theory of the 3×3 coupler-based demodulation algorithm and calibration method used in asymmetry coupler were presented.Secondly,the selection of minimum unbalanced interferometer path length,as well as the relation of system noise and frequency noise of laser were analyzed.Next,the amplitude of the maximum demodulated signal of NPS and the arctangent algorithm were compared.At last,the effect of differentiator on the dynamic range of NPS method was analyzed.The experiment results show that the dynamic range of NPS method is wider than that of arctangent algorithm,and a bad amplitude-frequency characteristic of differentiator will narrow the dynamic range of demodulation.The dynamic range of NPS algorithm and arctangent algorithm reaches to 96 dB and 91 dB respectively when the sampling frequency is 125 kHz,signal frequency is 1 kHz,and interferometer`s unbalanced length is 100 m.By applying calibration before demodulation,the 3×3 coupler-based demodulation methods may produce a large dynamic range,which can achieve a stable demodulation and meet the requirements of engineering application.%为了实现分布反馈式光纤激光传感器(DFB FL)大动态范围、稳定解调,建立了基于3×3耦合器的迈克尔逊干涉仪解调系统.对该系统所采用的对称解调算法(NPS)和反正切解调算法进行了深入研究.首先,介绍了基于3×3耦合器解调算法的原理及耦合器不对称时的调校方法.接着,对干涉仪所需最小非平衡路径长度的选取与系统强度噪声、激光器频率噪声的关系进行了分析.最后,针对NPS算法与反正切算法最大可解调信号幅度进行了分析对比,并研究了微分器对对称解调方法解调范围的影响.实验结果表明:NPS算法动态范围高于反正切算法,微分器的幅频特性不理想会减小解调动态范围.在采样频率为125 kHz、信号频率为1 kHz、干涉仪非平衡路径为100 m时,NPS算法与反正切算法的动态范围分别达到96 dB和 90 dB.用解调前调校的方法,基于3×3耦合的解调方法动态范围大,能够实现稳定解调,满足工程应用要求.