双光纤双参量布里渊光时域分析传感技术的研究

对于布里渊分布式光纤传感器(DOFS),温度或应变的变化都会引起布里渊频移谱改变,因此存在交叉敏感问题。在以往对布里渊光时域反射(BOTDR)计的双参量传感研究中,采用单根光纤,通过同时检测布里渊频移和功率变化,实现双参量传感。但对于布里渊光时域分析(BOTDA),由于受激布里渊散射的偏振相关性,不能实现对受激散射光功率的准确检测,因此难以实现单光纤的双参量传感。针对这一问题采用温度和应变系数不同的双光纤进行双参量传感。先测量了几种常用光纤的温度和应变布里渊频移系数,然后选择G652和G652成缆两种光纤,通过构建系数矩阵,由两根光纤的布里渊频移计算得出温度和应力,从而实现了温度分辨率25℃左右,应变分辨率约为200με的双参量传感。

Study on the Dual-Parameter Sensing Technology of Brillouin Optical Time Domain Analyzer Based on Dual-Optical-Fiber

For the Brillouin-based distributed optical fiber sensor(DOFS),the change of temperature or strain can cause the alteration of Brillouin frequency shift,so there exists the cross sensitivity problem.In the previous research of dual-parameter sensing of Brillouin optical time domain refrectometer(BOTDR),the frequency shift and optical power of the single fiber are detected simultaneously for dual-parameter sensing.However,for Brillouin optical time domain analyzer(BOTDA),because of the polarization-related stimulated Brillouin scattering,the power of the scattering light cannot be accurately detected and it is difficult to achieve dual-parameter sensing with a single fiber.Here two fibers with different temperature and strain coefficients are used for dual-parameter sensing.The temperature and strain coefficients of different optical fibers are obtained experimentally,based on which G652 fiber and G652 cable fiber are selected;their temperature and strain coefficients are used to construct the coefficient matrix.By simultaneously detecting these two optical fibers′ Brillouin frequency shift,temperature and strain are successfully sensed.The temperature resolution is about 25 ℃,and the strain resolution is about 200 με.