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.

根据导波光的微扰理论得到了线双折射磁光光纤光栅中导波光耦合模方程, 并给出了其解析解。借助于归一化斯托克斯参量, 研究了线双折射与磁圆双折射对光纤光栅中光偏振态的影响。研究表明, 线双折射磁光光纤光栅中存在左旋和右旋两个本征的椭圆光偏振态, 线双折射或磁圆双折射的大小只引起本征偏振态椭圆率的变化, 而不改变主轴方位角。通过调节磁光光纤光栅中两种双折射的相对大小可方便地控制输出导波光的偏振态, 从而使磁光光纤光栅在光纤通信与传感中具有广泛的潜在应用。