具有较大非平衡长度的光纤Mach－Zehnder干涉仪解调DFB激光器传感信号时，存在着偏振衰落现象，为了解决这一问题，提出了一种对干涉仪输入光偏振态进行反馈控制的方案，论述了具有反馈控制功能的干涉仪信号解调系统，推导了反馈控制系统的控制信号与干涉仪条纹可见度之间的关系式，分析了该系统在不同光信号输入情况下的工作状况，从理论上证明了利用该系统可在一定条件下使干涉仪的条纹可见度稳定在1附近，论证了该方案消除干涉仪解调传感信号时偏振衰落现象的可行性。

Demodulated by fiber optic Mach-Zehnder interferometer which has longer unbalance length,the sensing signal of DFB laser experiences the polarization induced fading. The feedback control scheme of interferometer input light polarization is introduced,which can be used to overcome the polarization induced fading. The interferometer signal demodulation system is discussed in detail,which has feedback control function. The relation between control signal and interferometer stripe visibility is deduced. The working process is analysed at different signal input condition. Theoretically the interference stripe visibility can be stabilized nearby 1 under a certain condition. The feedback control scheme can be used to eliminate the polarization induced fading.