光路系统的偏振误差极大地制约着双光程光纤陀螺精度的提高。为了提高新型双光程光纤陀螺的精度，利用相干矩阵和琼斯矩阵对光路中光学器件和熔接点的光学参数进行描述，通过分析顺时针光波与逆时针光波中耦合次波列与主波列间的相干叠加机理，建立了相应的偏振误差模型。利用Matlab以接近于工程实际的参数设置，对光路系统中熔接点、各光学器件缺陷对偏振误差的影响进行了仿真分析，并在此基础上提出了一种可有效抑制双光程光纤陀螺偏振误差的尾纤匹配法。仿真结果表明，通过适当的尾纤长度匹配，双光程光纤陀螺的偏振误差由0.145°/h减小为0.017°/h，其随温度变化的峰谷值也由0.25°/h减小至3×10-4°/h，双光程光纤陀螺的偏振误差得到有效抑制。

The polarization error of optical system limits the accuracy of fiber-optic gyroscope with double optical length. In order to improve the precision, the models of optical devices and fused points in the new gyroscope are described by using coherent matrix and Jones matrix. Based on the model mentioned above and interference analysis between secondary coupled wave-trains and principal wave-trains in the clockwise and counter clockwise direction, a physical model of polarization bias error of fiber-optic gyroscope with double optical length is established. With practical parameters setting, the influences of some apparatus on polarization noise are simulated and discussed, and furthermore, a new method of matching pigtails is especially presented, which can be used for decreasing the polarization error effectively. Simulation results demonstrate that the polarization bias error can be suppressed from 0.145°/h to less than 0.017°/h, and its peak-valley value of variation with temperature can be suppressed to less than 3×10-4°/h, through matching fiber length. The polarization bias error is suppressed effectively.