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。

According to the perturbation theory for guided optical waves, coupled-mode equations in linearly birefringent magneto-optic fiber Bragg gratings (LB-MFBGs) as well as its analytical solution are presented. Dependence of optical polarization state in the LB-MFBGs on linear birefringence and magnetically circular birefringence is in detail investigated by means of normalized Stokes parameters. It is shown that, in the LB-MFBGs there exist two eigenstates of polarization (left-handed and right-handed elliptically polarized light), and the birefringence effects only change the ellipticity, instead of the azimuth of principal axis. By changing the relative magnitude of the linear and circular birefringence, the output polarization states could be controlled, which is helpful for the potential applications of the LB-MFBGs in optical fiber communication and sensing.