为了在光纤陀螺等关键器件中使用超细径保偏光纤取代常用的普通直径保偏光纤，需要对其偏振轴的确定方法进行改进和优化。首先，使用光线追迹法对图像侧面成像对轴法在几种条件下的理论图像进行计算机仿真，并对仿真结果较好的两种情形进行实验验证；然后，对实验数据曲线进行傅里叶展开以抑制随机干扰，将结果较好的三亮纹方法改进为三亮纹四点特征法，并对该方法进行实验验证；最后，测定使用三亮纹四点特征法得到的重复精度。实验结果表明，该方法大大提高了超细径保偏光纤偏振轴定轴过程中的抗干扰能力，重复精度达到1.6°，达到了普通直径保偏光纤的偏振轴定轴精度，满足实际应用要求。

In order to replace the commonly used normal diameter Polarization Maintaining (PM) fiber with the ultra-fine PM fiber in fiber optic gyroscopes and other key components, the method of determining its polarization direction needs to be improved and optimized. First, theoretical images of side-view-image method were obtained by computer simulation using ray-tracing method. Then, the situations were verified whose simulated results were better, and the experimental curves were Fourier expanded to suppress random noise. The three-bright-line method whose experimental result was better was improved into three-bright-line-four-feature-point method, and this method was verified by experiments. Finally, the repeatability of this method was measured. Experimental results indicate that the three-bright-line-four-feature-point method has greatly increased the anti-jamming capability of the process of ultra-fine PM fiber polarization direction’s determining, and the repeatability achieves 1.6°. This result has reached the repeatability of common PM fiber polarization direction’s determining, and met the requirement of practical applications..