湿端结构极简的低噪声低串扰光纤光栅水听器阵列  

Low-Noise and Low-Crosstalk In-Line Interferometric Fiber Bragg Grating Hydrophone Array with Only FBGs at Wet End

作　　者：马丽娜[1] 尚凡 戚悦 卞玉洁 熊水东[1] Ma Lina;Shang Fan;Qi Yue;Bian Yujie;Xiong Shuidong(College of Meteorology and Oceanography,National University of Defense Technology,Changsha 410073,Hunan)

机构地区：[1]国防科技大学气象海洋学院,湖南长沙410073

出　　处：《光学学报》2023年第5期42-50,共9页Acta Optica Sinica

基　　金：国家自然科学基金(61901488)。

摘　　要：由于湿端极简化,光纤光栅水听器系统中普遍存在的偏振诱导信号衰落和随机相位衰落等关键问题仅能采用复合型调制解调手段解决;光纤光栅的双向反射特性会引起传感通道间信号串扰增加等新问题。报道了一种光纤光栅水听器阵列,水下仅采用80个光纤光栅构成64基元水听器阵列。采用相位生成载波与偏振切换调制解调方案,系统本底相位噪声达到■,等效噪声压为36 dB@1 kHz。系统采用低反射率光纤光栅,结合8空分×2波分×8时分复用结构设计,系统的时分、空分和波分通道串扰均稳定在-40 dB以下。该研究为光纤光栅水听器的工程实用化提供了重要的实践探索。Objective The in-line interferometric fiber Bragg grating(FGB)hydrophone array contains only FBGs at the wet end.The dramatically reduced number of undersea components and fusion points leads to high reliability,lightweight,and miniaturization,which makes the FBG hydrophone a promising candidate for future large-scale and highly-integrated applications.However,the special undersea structure brings technical challenges in solving the problems of polarization-induced signal fading and random phase fading,and the bidirectional reflections of the FBG may increase the channel crosstalk.Although the in-line interferometric FGB hydrophone array is considered to be the most promising next-generation hydrophone,the above-mentioned technical challenges must be solved before its application in harsh marine environments.Hence,this paper presents an in-line interferometric FGB hydrophone array to fully explore the system performance,providing experimental results before practical applications.Methods The presented in-line interferometric FGB hydrophone array contains 64 sensing channels.A simple undersea design structure with only 80 FBGs is adopted to form 8SDM(space division multiplexing)×2WDM(wavelength division multiplexing)×8TDM(time division multiplexing)multiplexing hydrophone channels.FBGs with reflectivity less than 1%are fabricated to suppress the multi-reflection-induced channel crosstalk.The undersea hydrophone unit has a mandrel structure with dimension ofϕ18 mm×50 mm,and the array has a diameter of 32 mm.A hybrid processing method of the phase generated carrier(PGC)and polarization switching(PS)is used to solve the polarization-induced signal fading and random phase fading problems simultaneously,and the PGC modulation frequency and PS modulation frequency are 12.5 kHz and 80 kHz,respectively.Results and Discussions The measured acoustic sensitivity is about(-131.15±1.15)dB,and the frequency response from 20 Hz to 2 kHz is presented with a fluctuation of less than±1.5 dB.The background phase noise is−95

关 键 词：光纤光学 光纤水听器 光纤光栅 本底相位噪声 等效噪声压 通道串扰 

分 类 号：O436[机械工程—光学工程]