基于FBG-FP腔的光纤矢量水听器研究

发布时间：2019-01-18 20:36

【摘要】：海洋资源的开发与领海权益保护日益受到国家的重视,水声技术是当前研究和探索海洋的主要手段。水听器作为水声探测的核心部件,其性能的好坏决定了整个系统性能的优劣。光纤矢量水听器具有性能可靠且易于复用等优点,但也存在裸光纤灵敏度不足且光纤本身较为脆弱等缺点,如何有效的改善这些缺点同时提高探测灵敏度和工作频带宽度是当下的研究热点。本文从光纤光栅法布里-珀罗(FBG-FP)腔的光谱特性出发,深入探讨了光纤FBG-FP的传感性能,并结合薄壁空心刚性圆柱结构理论,建立了光纤FBG-FP矢量声波传感理论模型,仿真与实验分析了传感器的加速度灵敏度与谐振频率受结构参数的影响。采用数字化相位生成载波(PGC)解调方法,搭建全光纤矢量水听器系统,实现了高灵敏度矢量声波探测。本文的主要工作有:1.开展了FBG-FP腔光谱特性研究。分析推导了光纤光栅(FBG)以及由其构成的法布里-珀罗(F-P)腔的光传输特性和反射光谱特性,设计了基于非平衡迈克尔逊干涉仪的相干检测光路并提出了抗随机相位衰落和消偏振衰落的方案。依据弱反射FBG-FP传感原理推导了系统干涉条纹的可见度函数,仿真分析了光谱、光程失配对光路相干性的影响。为实现高灵敏度的矢量声波探测系统奠定了基础。2.建立了薄壁圆柱的同振型光纤矢量声波敏感结构理论模型。仿真分析了芯轴材料、结构参数对矢量声波敏感探头的加速度灵敏度和频率特性的影响。通过优化参数,设计、制作了多个声敏感探头,并分别进行了加速度灵敏度和频率特性测试实验。实验结果表明:通过增加惯性元件质量、减小圆柱壳壁厚、增加柱体高度可有效提升探头加速度灵敏度。3.开展了数字化PGC解调方案与信号处理算法研究,仿真验证了全数字化信号处理算法的可行性。提出了波分复用结合低反射率FBG-FP的全光纤矢量水听器系统方案,分析了矢量声波信号探测原理,并实验验证了光纤矢量水听器的指向性,其垂直方向上的加速度灵敏度差值为-25 dB。4.搭建了全光纤矢量水听器系统,并设计了矢量水听器测试系统。开展了水听器指向性、灵敏度、频率响应等性能测试实验。实现了0.2-2 kHz的矢量声波探测,其加速度灵敏度为28 dB re rad/g。并实验测试了矢量水听器系统在二维平面内的指向性能。
[Abstract]:The exploitation of marine resources and the protection of the rights and interests of the territorial sea are paid more and more attention by the state. Underwater acoustic technology is the main means to study and explore the ocean. As the core component of underwater acoustic detection, hydrophone performance determines the performance of the whole system. The fiber vector hydrophone has the advantages of reliable performance and easy to reuse, but it also has the disadvantages of low sensitivity of the bare fiber and the weakness of the fiber itself. How to effectively improve these shortcomings and improve detection sensitivity and bandwidth is the current research focus. Based on the spectral characteristics of fiber Bragg grating Fabry-Perot (FBG-FP) cavity, the sensing performance of fiber FBG-FP is discussed in depth, and the structure theory of thin-walled hollow rigid cylinder is combined. The theoretical model of optical fiber FBG-FP vector acoustic sensing is established. The influence of structural parameters on the acceleration sensitivity and resonant frequency of the sensor is analyzed by simulation and experiment. The digital phase generated carrier (PGC) demodulation method is used to construct an all optical fiber vector hydrophone system and the high sensitivity vector acoustic wave detection is realized. The main work of this paper is as follows: 1. The spectral characteristics of FBG-FP cavity were studied. The optical propagation and reflectance spectra of fiber Bragg grating (FBG) and Fabry-Perot (F-P) cavity are analyzed and deduced. A coherent detection optical path based on an unbalanced Michelson interferometer is designed and a scheme to resist random phase fading and depolarization fading is proposed. Based on the weak reflection FBG-FP sensing principle, the visibility function of the interference fringes is derived, and the effects of spectrum and path mismatch on the coherence of the optical path are simulated and analyzed. For the realization of high sensitivity vector acoustic detection system laid the foundation. 2. A theoretical model of the fiber vector acoustic sensing structure for thin-walled cylinders is established. The effects of core material and structure parameters on the acceleration sensitivity and frequency characteristics of vector acoustic sensor are simulated and analyzed. By optimizing the parameters and designing, several acoustic sensors are fabricated, and the acceleration sensitivity and frequency characteristics are tested respectively. The experimental results show that by increasing the mass of the inertial element, decreasing the wall thickness of the cylindrical shell and increasing the height of the cylinder, the acceleration sensitivity of the probe can be raised effectively. The digital PGC demodulation scheme and the signal processing algorithm are studied, and the feasibility of the full digital signal processing algorithm is verified by simulation. An all-fiber vector hydrophone system with wavelength division multiplexing (WDM) combined with low reflectivity (FBG-FP) is proposed. The principle of vector acoustic signal detection is analyzed, and the directivity of the fiber vector hydrophone is verified by experiments. The difference of acceleration sensitivity in vertical direction is -25 dB.4.. An all-fiber vector hydrophone system is built and a vector hydrophone testing system is designed. The performance tests of hydrophone such as directivity, sensitivity and frequency response were carried out. The vector acoustic detection of 0.2-2 kHz is realized, and the acceleration sensitivity is 28 dB re rad/g.. The directional performance of vector hydrophone system in two-dimensional plane is tested experimentally.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB565.1

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