基于旋转半波片和交替电流测量的隧道超前探测光纤电流传感器灵敏度漂移补偿方法

Compensation Method for Tunnel Advanced Detection Fiber Optical Current Sensor’s Sensitivity Drift Based on Rotatable Half-wave Plate and Alternated Current Measurement

用于隧道超前探测中电流测量的光纤电流传感器受环境影响,灵敏度产生漂移。文中提出了基于旋转半波片和交替电流测量的灵敏度漂移补偿方法,由于传感器灵敏度在短时间内漂移量较小,故利用继电器快速切换使两部分待测电流交替穿过光纤环,对应的传感器输出电压取商以得到待测电流在已知总电流中的占比,进一步解出待测电流的大小,这种比例运算降低了长期测量中灵敏度漂移对测量结果的干扰。当传感器灵敏度过低影响交替电流测量的精度时,通过旋转半波片产生一个特定大小的双折射,提高传感器灵敏度。两种手段相结合的工作模式能够适应隧道内复杂的环境变化,现场实验表明,在4 h的测量中,传感器灵敏度漂移离散系数高达31.8%,但应用了基旋转半波片和交替电流测量的灵敏度漂移补偿方法后漂移的离散系数降低至1.39%,满足隧道超前探测中聚焦电流法对电流的测量要求。

The optical fiber current sensor used for current measurement in tunnel advance detection is influenced by environment and its sensitivity drifts.In this paper,compensation method based on rotatable half-wave plate and alternated current measurement was developed.Experiments show that the sensor sensitivity drifts less in a short time.Hence,with the assist of relay,currents pass through the sensor s optical fiber loop alternatively,and their corresponding sensor s output voltages are collected to calculate each current s proportion of the whole.The magnitude of the current to be measured is further solved.This scale operation reduces the interference of sensitivity drift to the measurement results in the long-term measurement.In addition,when the sensitivity drifts too weak to disturb the alternated current measurement method,a rotatable half-wave plate is activated to generate a proper linear birefringence and increase the sensitivity.The combined working mode of the two means can adapt to the complex environmental changes in the tunnel.Field experiments show that in the 4-hour measurement,the discrete coefficient of sensor sensitivity drift is as high as 31.8%,but after using the sensitivity drift compensation method based on rotating half-wave plate and alternating current measurement,the discrete coefficient of drift is reduced to 1.39%,which meets the current measurement requirements of focusing current method in tunnel advance detection.