基于块匹配三维滤波算法的长距离BOTDR系统研究  

Long⁃range BOTDR Using Block Matching and 3D Filtering Algorithm

作　　者：刘羽婷 张建国 白清 姚志玺 王璇 王宇[2] 靳宝全 Liu Yuting;Zhang Jianguo;Bai Qing;Yao Zhixi;Wang Xuan;Wang Yu;Jin Baoquan(Key Laboratory of Advanced Transducers and Intelligent Control System of Ministry of Education and Shanxi Province,Taiyuan University of Technology,Taiyuan 030024,Shanxi,China;College of Electronic Information and Optical Engineering,Taiyuan University of Technology,Taiyuan 030024,Shanxi,China)

机构地区：[1]太原理工大学新型传感器与智能控制教育部与山西省重点实验室,山西太原030024 [2]太原理工大学电子信息与光学工程学院,山西太原030024

出　　处：《中国激光》2024年第14期191-200,共10页Chinese Journal of Lasers

基　　金：国家自然科学基金(62005190);山西省重点研发计划项目(202202130501004,202302150101014);山西省基础研究计划资助项目(202303021221032);中央引导地方科技发展资金项目(YDZJSX20231B004)。

摘　　要：长距离布里渊光时域反射仪(BOTDR)存在光信号衰减较大、信噪比较低的问题,致使待测光纤信号功率极弱处所测得的布里渊频移(BFS)波动幅度及噪声明显增大。采用块匹配三维滤波算法(BM3D)对BOTDR测量信号进行降噪以提升系统测量精度。阐述了BOTDR信号特征,分析了基于BM3D的BOTDR降噪原理,搭建了基于后向拉曼放大方法的长距离BOTDR系统,并在100 km传感光纤上进行了实验验证。研究结果证明,在20 m空间分辨率及100次累加平均次数下,BM3D算法降噪前后光纤全段BFS波动幅度由±15.761 MHz降至±2.276MHz,均方根误差(RMSE)由6.477 MHz降至1.028 MHz。同时,降噪后光纤全段BFS波动幅度分布平滑,有效抑制了信噪比较低处BFS波动的大幅增加,进一步证明了该算法的有效性。Objective In long-range Brillouin optical time-domain reflectometer(BOTDR) sensors, owing to the excessive attenuation of optical signals and low signal-to-noise ratio(SNR), the BFS fluctuation range measured at a certain position of the fiber can be significantly larger than that at other positions. Solving this problem by only increasing the average number of traces is challenging.Increasing the average trace time significantly increases the measurement time and degrades the real-time performance of the sensor.Therefore, an effective denoising method must be devised to prevent the BFS fluctuation range from increasing, decrease the trace average time, and improve the measurement accuracy of long-range BOTDRs.Methods In this study, an backward Raman amplification scheme was used to improve the energy of a Brillouin backscattered signal, avoid nonlinear effects, and increase the sensing distance. Simultaneously, block matching and 3D filtering algorithm(BM3D)were introduced to solve the problem of expanding BFS fluctuation range in long-range BOTDRs. The search window used to identify similar blocks in the BM3D algorithm was adjusted to a rectangle, which increased the search range in the distance direction and rendered it more adaptive to the BGS-distance matrix.Results and Discussions At a sensing distance of 100 km, with a spatial resolution of 2 m and trace average number of 100, the BFS fluctuation range reduced from ±15.761 to ±2.276 MHz before and after denoising(Fig. 6), and the BFS fluctuation range is consistent throughout the fiber. The BFS fluctuation range is ±6.598 MHz under trace average number of 10000, and it continues to increase at the position featuring the lowest SNR. The maximum RMSE value is reduced from 6.477 to 1.028 MHz before and after denoising, and the maximum root mean square error(RMSE) value is ±3.246 MHz under an average of 10000 trace times(Fig. 8). In addition, the linearity and spatial resolution remains almost unchanged before and after denoising(Figs. 9 and 10). Finally,

关 键 词：光纤传感 信噪比提升 块匹配三维滤波算法 布里渊光时域反射仪 

分 类 号：TP212.1[自动化与计算机技术—检测技术与自动化装置]