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8 kHz时，系统噪声达到了-96 dB/Hz （1 kHz），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。

The interferometric fiber sensor is applicable in many fields for its high sensitivity, but the polarization induced signal fading is a serious problem. We proposed an orthogonal-polarization switching method and a signal synthesis algorithm based on the phase generated carrier (PGC) scheme to solve the problem for the pulse interrogation. The principle of the method was demonstrated and an algorithm for signal synthesis was derived based on the PGC scheme. The experimental results show that the equivalent visibility is steady between 0.93 and 0.94, and the background noise of the synthesized signal is lower than that of all the four polarization channels. The method can eliminate the polarization induced low frequency phase drift as well, making the synthesis results not influenced by perturbation of polarization states. The long time measurement results demonstrate that the background noise can reach -96 dB/Hz at 1 kHz when the frequency of the PGC demodulation was 8 kHz. This result is equivalent to that of the system with the Faraday rotator mirrors. This method is applicable for solving the signal fading problem in the time division multiplexing sensor array especially for the inline interferometric fiber sensor array based on fiber Bragg gratings and the distributed sensor array.