Polarization fading control for dual Mach-Zehnder fiber interferometric sensing system

• 1、College of Precision Instrument and Opto-electronics Engineering, Tianjin University, TianJin 300072
• 2、College of Precision Instrument and Opto-electronics Engineering, Tianjin University, Tianjin 300072

Abstract：In the dual Mach-Zehnder fiber interferometric sensing system, the high locating accuracy is hardly obtained due to the discrepancy of two detection signals resulting from polarization fading. To keep the stability of the detection signals, the optical polarization model is established to analyze the origin of polarization fading in the system. Because of the inconsistency of the polarization characteristics between two sensing fibers, the input polarization affects the detection signals, which is the basic reason for the degeneracy of the detection signals’ correlation. Based on the analysis, the solution of controlling the input polarization to eliminate polarization fading is put forward. The requirements of polarization control are further determined by analyzing the relation between the signal correlation coefficient and two parameters of input polarization, and Simulated Annealing is applied to verify this theory. Field test results show that, the algorithm can make a fast search for the working point of polarization state, and maintain a steady signal correlation. It is proved that the polarization fading control method is feasible and effective.

Keywords： Precision Instruments and Machinery Coherence optics Mach-Zehnder fiber interferometer Polarization fading Correlation coefficient Simulated Annealing Polarization control