基于BGO晶体的反射型法拉第光纤电流传感器

Optical Fiber Current Sensor Based on BGO Crystal with Enhanced Faraday Rotation by Reflections

采用Bi4Ge3O12(BGO)晶体作为传感元件,设计了一种闭合磁环型光纤电流传感器,并对其传感特性进行了理论分析和实验研究.将BGO晶体加工成一带斜面的长方体,并在端面镀金属膜,通过光在晶体中多次临界反射来增大光程以提高测量灵敏度.实验测量得到的法拉第转角与采用倍频法测量的结果符合较好,但与实际结果存在一较大比例系数.对产生该系统误差的主要因素——传感头端面金属膜反射引起的相移及入射角偏离临界角时产生的相移进行了详细地理论分析和数值模拟.结果表明,金属膜反射和偏离临界角引起的相移对测量结果均有较大影响,但输出与作用在传感头上的磁感应强度呈很好的线性关系,可以通过将传感器的测量值乘上一个补偿系数来消除反射相移所产生的误差.

An optical fiber current sensor （OCS） based on a BGO crystal with a magnetic field concentrator and enhanced Faraday rotation by critical angle reflections is designed and experimentally demonstrated. The influences of the phase shift caused by reflection,which is the main resource of the deviation between the measured and the real values, are theoretically analyzed and numerically simulated. It is demonstrated that the output is very sensitive to the degree of deviation from the reflection critical angle. The phase shift introduced by the reflections of the aluminium films changes linearly as the variations of magnetic field is also demonstrated. So the distortion of the output response due to aluminium coating can be corrected by multiplying a coefficient. It is demonstrated that an OCS based on BGO crystals with enhanced Faraday rotation could be developed into a practical OCS with a good linearity and a large dynamic range.