The coupling between guided optical waves in magneto-optic fiber Bragg gratings (MFBGs) with linear birefringence is investigated using the eigen-mode and coupled-mode approaches. The relationship between the polarization-dependent loss (PDL) and the eigen states of polarization (SOPs) in the MFBGs is discussed. Only the MFBGs with low linear birefringence are applied to the peak PDL-based magnetic field measurement, after which the linear dynamic range is determined using the relative magnitude of linear and magnetically induced circular birefringence. In this letter, a theoretical model is presented to explain the experimental results and help develop novel MFBG-based devices.

分段磁光光纤布拉格光栅(MFBG)是指在同一根磁光光纤上依次写入不同周期的光栅而形成的级联磁光光栅系统。根据均匀MFBG的耦合模理论,利用电磁场边界连续性条件,研究了分段MFBG中圆偏振光的光谱特性。研究表明,单段光栅时,圆偏振光在分段MFBG中的反射或透射光谱特性与均匀MFBG一致,理论计算的偏振相关损耗(PDL)变化曲线与实验结果基本吻合。两段或多段MFBG段级联时,分析了在外加磁场的控制下采用不同光栅周期的多段MFBG结构实现可调色散补偿、分布式磁场传感等光子信息处理的功能原理。