提出了一种基于光纤光栅中法拉第效应和测量偏振相关损耗的直接测量磁场的新方法,给出了理论分析和实验结果。当有外加磁场时,光纤光栅中的法拉第效应使两个圆偏振光的传播常量改变,从而导致光纤光栅的偏振相关损耗的变化。仿真结果表明,外加磁场与偏振相关损耗峰值在一定的测量范围内存在线性关系,测量结果对温度变化不敏感。分析了光栅的参量对测量性能的影响。实验中得到该方案测量磁场的灵敏度为7.8e-6 dB/Gs,利用现有精度为10-5 dB的光矢量分析仪得到最小可测磁场为2 Gs。实验与理论吻合较好。

A new magnetic field measurement method based on Faraday effect and measurement of polarization-dependent loss (PDL) in fiber grating was proposed and analyzed in theory and experiment. When the external magnetic field is applied, the transmission constants of the two circularly polarized lights in fiber grating will be changed by the Faraday effect, and so does the PDL of fiber grating. The simulations show there is a linear relationship between the peak value of PDL and magnetic field in a certain range. Moreover, this method is insensitive to temperature. The influence of parameters of grating on measurement performance was analyzed. The measurement sensitivity is 7.8e-6 dB/Gs and the precision is 2 Gs using the optical vector analyzer with 10-5 dB precision in experiment, which agree well with the theoretical analysis.