The research of polarization feedback control system based on double Mach-Zehnder interferometer

Polarization induced signal fading always has an influence up on the visibility of the interference stripe and the accuracy of system location in the distributed optical fiber oil &gas pipeline leak detection system. Base on distributed sensor system polarization characteristic, this paper analyses the visibility of the interference stripe with the changing of polarization. Designed a feedback control system based on double Mach-Zehnder is used to eliminate the input light polarization fading. This system can effectively suppress the polarization fading in fiber optical sensor, making interferometer fringe visibility tends to I and the equilibrium state of input light polarization always closes to the best input sate of interferometer.