基于超弱光纤布拉格光栅的高信噪比分布式振动传感系统

Distributed Vibration Sensing System with High Signal-to-Noise Ratio Based on Ultra-Weak Fiber Bragg Grating

提出了一种基于超弱光纤布拉格光栅的高信噪比(SNR)分布式振动传感系统。该系统用3 dB带宽超过3.4 nm、反射率为10-5的在线制备啁啾光栅阵列作为传感光纤,通过典型双脉冲调制方式和3×3耦合器进行相位解调。为了消除激光器、调制器和光放大器等光学元器件带来的各类噪声干扰,结合最小均方算法和对称探测结构进行自适应滤波。实验结果表明,相比小波去噪算法,本算法能有效降低系统噪声,最大可将1 kHz解调信号的高频本底噪声降低40.1 dB,SNR达到96.5 dB;对于2 km长的传感光纤,系统在1~5 kHz的应变灵敏度可达到13.66 pε/√Hz。

A distributed vibration sensing system with a high signal-to-noise ratio(SNR) based on an ultra-weak fiber Bragg grating is proposed in this paper. The system uses an online inscribed chirped grating array with a 3 dB bandwidth greater than 3.4 nm and a reflectivity of 10-5 as the sensing fiber, and phase demodulation is realized through typical dual-pulse modulation and a 3×3 coupler. To eliminate interference noises from optical components including laser, modulator, and optical amplifiers, we employ the least mean square algorithm and a symmetric detection structure for adaptive filtering. The experimental results show that compared with the wavelet denoising method, the method can greatly decrease the system noise. It can reduce the high-frequency noise floor of the 1 kHz demodulated signal by 40.1 dB at the maximum, and the SNR is as high as 96.5 dB. For the 2 km long sensing fiber, the strain sensitivity of the system reaches 13.66 pε/√Hz at 1--5 kHz.