基于弱光栅阵列增强的Φ-OTDR传感系统性能分析

The analysis of improved phase-OTDR sensing system employing weak fiber Bragg grating array

在基于弱光栅阵列增强的相位敏感光时域反射技术(Φ-OTDR)传感系统中,通过以弱光栅阵列(FBG)的反射信号代替传统Φ-OTDR中的瑞利散射信号,并通过匹配干涉仪来解调出相位变化,实现分布式测量。本文研究了弱光纤光栅阵列对Φ-OTDR振动传感系统信噪比(SNR)改善的效果,并分析了随之带来的串扰影响。实验结果表明,相比于传统Φ-OTDR传感系统,采用约-35 dB反射率弱光栅阵列增强的Φ-OTDR传感系统有着更低的相位噪声水平,信噪比提高了33 dB;由于弱光栅阵列中的串扰影响,在光纤2.4 km处的噪声水平相比于入射端上升了18 dB,但仍然好于无光栅阵列的Φ-OTDR系统。

Fiber Bragg grating(FBG) array has been extensively applied in various fields as a mainstream optical sensing technology. In an improved phase sensitive optical time domain reflection(Φ-OTDR) technology sensing system based on weak fiber Bragg grating(FBG) array,the Rayleigh scattering signals are replaced by the reflection signals of the weak FBG array,and the phase change is solved by a matching interferometer. In this paper,the effect of weak FBG array on the improvement of signal-to-noise(SNR) and the decrease of noise in a Φ-OTDR vibration sensing system is studied,and the crosstalk caused by multiple reflections in the improved system is analyzed. The results show that compared with traditional Φ-OTDR vibration sensing system,the system with-35 dB reflectivity FBG array has a lower phase noise level and its SNR is improved by 33 dB. Due to the influence of crosstalk,compared with the first FBG,the noise at the end of the sensing fiber is increased by 18 dB. However,the performance of the system based on FBG array is still better than the Φ-OTDR system without FBG array and keep a high SNR level.Thus,the introduction of weak FBG array has a positive influence on improving SNR and reducing noise.