Wang Xiaxiao, Zhao Zijie, Li Chuansheng, Yu Jia, Wang Zhenjie
Appl Opt. 2017 Nov 10;56(32):8887-8895. doi: 10.1364/AO.56.008887.
Bias error, along with scale factor, is a key factor that affects the measurement accuracy of the fiber-optic current sensor. Because of polarization crosstalk, the coherence of parasitic interference signals could be rebuilt and form an output independent of the current to be measured, i.e., the bias error. The bias error is a variable of the birefringence optical path difference. Hence, when the temperature changes, the bias error shows a quasi-periodical tendency whose envelope curve reflects the coherence function of light source. By identifying the key factors of bias error and setting the propagation directions of a super-luminescent diode, polarization-maintaining coupler and polarizer to fast axis, it is possible to eliminate the coherence of parasitic interference signals. Experiments show that the maximum bias error decreases by one order of magnitude at temperatures between -40°C to 60°C.
偏置误差与比例因子一样，是影响光纤电流传感器测量精度的关键因素。由于偏振串扰，寄生干扰信号的相干性可能会重建，并形成与待测电流无关的输出，即偏置误差。偏置误差是双折射光程差的一个变量。因此，当温度变化时，偏置误差呈现准周期性趋势，其包络曲线反映了光源的相干函数。通过识别偏置误差的关键因素，并将超发光二极管、保偏耦合器和偏振器的传播方向设置为快轴，可以消除寄生干扰信号的相干性。实验表明，在-40°C至60°C的温度范围内，最大偏置误差降低了一个数量级。
