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干涉型光纤传感器是一种高灵敏度的传感器,在许多领域都具有重要应用价值,而偏振衰落是这种传感器中需要解决的一个重要问题。提出采用脉冲正交偏振切换及基于相位生成载波(PGC)的信号合成算法来实现抗偏振衰落。阐述了正交偏振切换方法的基本理论,分析了以PGC解调为基础的正交偏振切换合成算法的原理,搭建了实验系统进行实验研究。结果表明,当光纤中偏振态受到扰动时,通过正交偏振切换及合成算法,合成的结果等效干涉度可以稳定在0.93~0.94之间;解调结果的噪声可以达到四路偏振通道噪声的最低水平。该方法可以消除传输光纤中偏振扰动所造成的低频相位漂移,使解调结果不受传输光纤中偏振态扰动的影响。长时间的噪声监测结果表明,PGC调制频率为8kHz时,系统噪声达到了-96dB/槡Hz(1kHz),与同一系统中采用法拉第旋镜作为反射镜测得的本底噪声相当。该方法为解决干涉型光纤传感器时分复用阵列,特别是基于光纤光栅的干涉型准分布式光纤传感器和分布式传感系统中的偏振衰落问题提供了一种可行的途径。
Interferometric fiber optic sensors are highly sensitive sensors that have important applications in many fields. Polarization fading is an important issue that needs to be addressed in this sensor. The anti-polarization fading is proposed using pulse orthogonal polarization switching and signal synthesis algorithm based on phase-generated carrier (PGC). The basic theory of orthogonal polarization switching method is expounded, the principle of orthogonal polarization switching synthesis algorithm based on PGC demodulation is analyzed, and the experimental system is set up for experimental research. The results show that the equivalent interference of the synthesized results can be stabilized between 0.93 and 0.94 by the orthogonal polarization switching and combining algorithm when the polarization state of the fiber is disturbed. The noise of the demodulation result can reach the noise of four polarization channels Lowest level The method can eliminate the low-frequency phase shift caused by the polarization disturbance in the transmission fiber so that the demodulation result is not affected by the polarization state disturbance in the transmission fiber. Long-term noise monitoring results show that the system noise reaches -96dB / 槡 Hz (1kHz) when the PGC modulation frequency is 8kHz, which is equivalent to the noise floor measured using a Faraday rotator as a reflector in the same system. The method provides a feasible approach for solving the problem of polarization fading in the time-multiplexed array of an interferometric optical fiber sensor, in particular, an interference type quasi-distributed optical fiber sensor based on a fiber grating and a distributed sensing system.