光纤光栅水听器链路瑞利寄生干涉噪声研究  

Analysis on Rayleigh Parasitic Interference Noise of the Leading Fiber in Interferometric Fiber Grating Hydrophone

作　　者：卞玉洁 胡琪浩 马丽娜[1] 余懿 戚悦 潘彤 Bian Yujie;Hu Qihao;Ma Lina;Yu Yi;Qi Yue;Pan Tong(College of Meteorology and Oceanography,National University of Defense Technology,Changsha,Hunan 410073,China)

机构地区：[1]国防科技大学气象海洋学院,湖南长沙410073

出　　处：《中国激光》2024年第23期95-105,共11页Chinese Journal of Lasers

基　　金：国家自然科学基金(42376189);国防科技大学“金点子”项目(2023-ZZCX-JDZ-47)。

摘　　要：光纤光栅水听器在水下目标探测、海洋资源勘探、海洋背景噪声测量等海洋领域中有着广泛的应用。由于光纤光栅水听器通常采用反射率低于5%的弱反射率光栅,在经过多个光栅反射后可达到与瑞利散射比拟的数量级,因而对链路瑞利寄生干涉的敏感性更高。针对光纤光栅水听器阵列建立了链路光纤瑞利寄生干涉模型,提出高敏感性瑞利散射段概念。理论分析表明:链路光纤高敏感性瑞利散射段的个数和位置分布与链路光纤长度、询问频率相关,每个高敏感性瑞利散射段的长度与两光栅之间的光纤长度相同。高敏感性瑞利散射段的存在会将其与光纤光栅水听器基元之间链路上的干扰通过寄生干涉引入到水听器相位解调结果中,导致系统本底噪声抬升。实验结果表明:链路光纤瑞利寄生干涉会导致光纤光栅水听器阵列本底噪声水平产生阶跃性跳变,跳变前后噪声信号的响应幅度差异最大可达10 dB左右。在阶跃性跳变之后,随着高敏感性瑞利散射段数量的增加,光纤光栅水听器阵列的噪声信号幅度增加较为缓慢,在不引起非线性效应的前提下,以分布概率不小于90%为约束,每增加一个高敏感性瑞利散射段,光纤光栅水听器阵列的噪声信号幅度增加约5 dB。Objective Fiber-optic grating hydrophones have a wide range of marine applications,such as underwater target detection,marine resource exploration,and ocean background noise measurements.As fiber grating hydrophones usually use weak reflectivity gratings with a reflectance below 5%,they can reach an order of magnitude comparable to that of Rayleigh scattering after multiple grating reflections and are therefore more sensitive to Rayleigh parasitic interference of the leading fiber.In this study,a leading fiber Rayleigh parasitic interference model is developed for fiber-grating hydrophone arrays,and the concept of highly sensitive Rayleigh scattering segments is proposed.Theoretical analyses show that the number and spatial distribution of high-sensitivity Rayleigh scattering segments in the leading fiber are related to the length of the leading fiber and the interrogation frequency and that the length of each high-sensitivity Rayleigh scattering segment is the same as the length of the fiber between the two gratings.The high-sensitivity Rayleigh scattering segments introduce interference in the leading fiber between them and the fiber grating hydrophone units.The parasitic interference introduced into the hydrophone phase demodulation results in an increase in the system background noise.The experiments reveal that Rayleigh parasitic interference in the leading fiber can cause a step change in the background noise level of the fiber grating hydrophone array,with a maximum difference in the response amplitude of approximately 10 dB before and after the jump.After the jump,the amplitude of the noise signal increases more slowly as the number of highly sensitive Rayleigh scattering segments increases, with the amplitude of the noise signal increasing by approximately 5 dB for each additional highly sensitiveRayleigh scattering segment without causing nonlinear effects, subject to the constraint that the distribution probability is no less than90%.Methods In this study, a model of leading fiber Rayleigh parasitic in

关 键 词：光纤光学 光纤光栅水听器 瑞利散射噪声 寄生干涉 链路噪声 

分 类 号：O436.1[机械工程—光学工程]