双Mach-Zehnder光纤干涉传感系统中的偏振衰落控制

Control of polarization fading for dual Mach-Zehnder fiber interferometric sensing system

针对偏振衰落现象导致信号关联的二义性使分布式双Mach-Zehnder光纤干涉传感系统难以实现高精度定位的问题,提出了一种控制偏振衰落的方法来保持系统检测信号的稳定性。利用系统的偏振模型分析了偏振衰落的来源,指出传感光纤偏振特性的不一致使系统检测信号对输入偏振态敏感是造成信号相关性恶化的根本原因,据此提出控制输入偏振态、搜索偏振态工作点的抗偏振衰落思想。在此基础上通过分析输入偏振态的两个参量对信号相关系数的作用进一步明确了偏振控制对算法的要求,并利用模拟退火算法进行了验证。现场实验表明,该算法可快速搜索偏振态工作点,持续稳定系统检测信号的相关性;结果证实了提出的偏振衰落控制方法可行且有效。

Abstract： In a dual MachZehnder 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, a method to control the polarization fading was proposed in this paper. A optical polarization model was established to analyze the origin of polarization fading in the system. It points out that the basic reason for the discrepancy of the detection signal correlation is from that the inconsistency of the polarization characteristics between two sensing fibers results in the effect of the input polarization on detection signals. Based on the analysis, the solutions of controlling the input polarization and searching for the working points of polarization state were put forward to e liminate the polarization fading. Furthermore, the requirements of polarization control were further determined by analyzing the relation between signal correlation coefficients and two parameters of input polarization, and simulated annealing was applied to the verification of this theory. Field test re sults show that the algorithm can make a fast search for the working points of polarization state, and can maintain a steady signal correlation. It is proved that the polarization fading control method is fea sible and effective.