基于弱光纤光栅阵列的分布式振动探测系统

Distributed Vibration Detection System Based on Weak Fiber Bragg Grating Array

基于时分复用技术,提出了一种分布式弱光纤光栅(FBG)阵列振动探测系统。通过匹配干涉仪检测相邻弱FBG的干涉信号,可以得到振动信号的频率、相位和位置等相关信息,从而实现高灵敏度分布式测量。使用3×3相位解调方法对干涉信号进行解调,可以有效地降低系统的相位噪声。采用光栅个数为660、间距为2.5m的弱FBG阵列对该系统进行了验证。实验结果表明,系统的干涉条纹可见度与相邻弱FBG的波长差有关;同时,系统能准确地分辨出不同频率的信号,频率响应范围在20~1000Hz之间,具有很好的频率响应;与标准的地震检波器对比发现,该系统传感单元具有更高的灵敏度。

Based on time division multiplexing technology, a distributed weak fiber Bragg grating （FBG） array vibration detection system is proposed. By using a path-match interferometry method, the interference signals between two adjacent weak FBGs are detected, and relevant information of vibration such as phase, frequency and location is obtained, thus we can achieve high sensitivity distributed measurement. The 3 × 3 phase demodulation technique is employed to effectively eliminate signal fading in the interferometer. The feasibility of the system is verified by a weak FBG array with 660 gratings and 2.5 m distance between adjacent FBGs. Experimental results show that the interference fringe visibility is related to the wavelength difference between adjacent weak FBGs. Meanwhile, the proposed system can accurately distinguish weak signal with different frequencies （ranging from 20 Hz to 1000 Hz） and has better frequency response. The sensor system has higher sensitivity in contrast to standard seismic geophone.