采空区沉降监测的BOTDR光纤传感技术

摘要

基于布里渊光时域反射计(BOTDR)设计了应变检测系统,用于采空区的沉降监测.该系统使用窄线宽激光器和高消光比光调制器产生脉冲光,并通过相干探测和微波扫频获取高信噪比的原始信号,最后采用洛仑兹曲线拟合算法解调出布里渊频移分布曲线.实验中,选用10.19 km的传感光纤,在末端3.9 m长度光纤上施加不同应变,以模拟采空区的沉降,解调的频移误差为2.1 MHz,对应应变测量误差为48.7 με,该系统能为采空区的沉降监测提供一种方案和技术.%The strain detection system was designed based on a Brillouin optical time domain reflectometer(BOTDR)for monitoring the goaf subsidence,in this paper.System used a narrow linewidth laser and a high-extinction-ratio light modulator to generate the pulse probe light,and acquired the original signal with high signal-to-noise ratio by coherent detection and microwave scanning.Then,the Lorenz curve fitting algorithm was utilized to obtain the distribution of the Brillouin frequency shift along the sensing fiber.Finally,the 10.19 km sensing fiber was chosen,and different strain was imposed on the 3.9 m segement of the fiber end to simulate the subsidence of the goaf.Experiment results demonstrate that the demodulation error of frequency shift is about 2.1 MHz and the corresponding strain measurement error is 48.7 με.The system can provide a solution and technology for subsid-ence monitoring of the goaf.