磁光调制法测量高双折射光纤拍长的灵敏度分析

Sensitivity Analysis of Magneto-optic Modulation Method in Measuring Beat Length of Birefringence Optical Fiber

基于法拉第磁光效应,研究在光纤拍长磁光调制法测试系统中,对于给定的磁隙宽度和磁场强度,起偏方式与检偏方式对拍长测试灵敏度的影响.通过理论分析发现,除了目前通常采用的线偏振光沿光纤双折射主轴注入结合渥拉斯顿棱镜45°检偏的测试方式之外,另有两种测试方式也可以得到最大灵敏度,一种是线偏振光45°注入结合渥拉斯顿棱镜沿轴检偏,另一种是圆偏振光注入结合渥拉斯顿棱镜沿轴检偏.最后一种实验方式不需要在入射端精确定位光纤的双折射主轴方向,能简化实验过程,避免角度调节引入的测量误差.

Based on Faraday effects in birefringence optical fiber, we study the influence of the polarized style and the style of analysis on the measurement sensitivity of beat-length. This is done by using magneto-optic modulation techniques in which the magnetic gap and magnetic intensity are known. In a commonly used style, the input light is linearly polarized and parallel to the birefringence axis of the fiber, and the two analyzing axes of Wollaston prism make 45° with the birefringence axis of the fiber. In addition to this style, two other experimental styles are found to provide high sensitivity. In one of these styles, the input light is linearly polarized having an angle of 45° with respect to the birefringence axis of the fiber, and the Wollaston prism is parallel to the birefringence axis. In the other style, the input light is circularly polarized and the Wollaston prism is parallel to the birefringence axis. The latter does not require accurate birefringence axis direction at the input end. This makes experiments more convenient and can reduce measurement error due to angle adjustment.