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从原理上阐述了圆双折射光纤光栅中的传输特性和偏振特性。通过坐标变换,得到圆双折射光栅的琼斯矩阵,并基于此详细分析了磁场大小、传输距离和入射光偏振态对透射光传输特性和偏振特性的影响。结果表明,一定大小的磁致圆双折射将使透射谱产生分裂,透射光偏振态随磁场和波长变化。同时偏振相关损耗和第三斯托克斯参量与外加磁场大小在一定范围内呈单调变化关系,可由此实现对磁场的监测。测量范围和灵敏度由光栅材料和结构决定,给出了由Bi-YIG和YIG材料作为传感媒质可实现的动态范围。
In principle, the transmission and polarization characteristics of circular birefringent fiber gratings are expounded. The Jones matrix of the circular birefringent grating is obtained through coordinate transformation. Based on this, the influence of the magnetic field, the transmission distance and the polarization state of incident light on the transmission and polarization characteristics of transmitted light is analyzed in detail. The results show that the circular birefringence of a certain size will cause the splitting of the transmission spectrum and the polarization of the transmitted light will change with the magnetic field and the wavelength. At the same time, the polarization-dependent loss, the third Stokes parameter and the applied magnetic field have a monotonously changing relationship within a certain range, thus the monitoring of the magnetic field can be realized. The measurement range and sensitivity are determined by the grating material and structure, giving the dynamic range achievable with Bi-YIG and YIG materials as sensing media.