【作者】 马丽娜；

【导师】 胡永明；

【作者基本信息】 国防科学技术大学 ， 光学工程， 2010， 博士

【摘要】 光纤激光水听器是随着近年来掺杂光纤制作技术、光敏光刻技术和光纤激光器技术的发展而出现的一种新型高精度光纤水声传感手段。光纤激光水听器采用线型腔光纤激光器作为水声敏感基元,采用非平衡干涉仪对水声信号进行解调,具有灵敏度高、体积小、复用结构简单等优点,特别适合用于构造大规模超细光纤水听器阵列。本文结合实验室多年来对光纤水听器系统理论、实验及工程研究的经验,对光纤激光水听器技术进行深入分析,寻求光纤激光水听器工程应用的正确方法。论文的研究内容包括线型腔光纤激光器技术、光纤激光水听器信号解调技术、封装技术和复用技术。对线型腔光纤激光器的模式控制和噪声水平进行了深入分析,实验制作了线型腔光纤激光器并对其各项指标进行了详细测试;建立了光纤激光水听器的声压模型,分析了最小可测声压强度,建立了多纵模光纤激光水听器的信号处理模型,分析了采用相位载波方案(PGC,Phase Generated Carrier)对多纵模光纤激光水听器进行解调时的信号衰落现象并得到实验验证,采用干涉仪臂差匹配方案实现了多纵模光纤激光水听器的稳定解调;设计了一种金属和弹性材料混合封装结构,在增敏和频率响应平坦化两个方面取得良好效果;对波分复用阵列中传感基元的特性变化进行了对比分析和测试,对串联形式的阵列复用容量进行了理论和实验综合分析,测量了光纤激光水听器波分复用阵列的信道串扰。论文的主要研究成果和创新性如下:1.论文对掺铒和铒镱共掺线形腔光纤激光器分别建立了强度噪声模型,设计并研制成上述结构的光纤激光器,实验与理论模型结果一致。2.基于PGC原理,采用干涉仪臂差匹配方案,成功对多纵模光纤激光水听器实现了稳定解调。3.设计并研制成一种金属和弹性材料混合封装光纤激光水听器,其最大声压灵敏度接近目前报导的最高值,波动指标优于之前报导的各种结构。4.建立了波分复用阵列中光纤激光水听器基元的强度噪声模型,提出利用驰豫振荡频率随泵浦功率变化的规律判定阵列中各基元的实际泵浦功率的方法,并对强度噪声随基元数目而增加进行了初步实验研究。更多还原

【Abstract】 Fiber laser hydrophone takes the advantages of recent revolution in doped fiber fabrication, fiber grating and fiber laser techniques to perform as a novel acoustic sensing scheme with high sensitivity. It utilizes short linear cavity laser to act as in-fiber acoustic sensing device and has a number of perceived benefits, such as high sensitivity, easily multiplexing capability, miniature size, and so on, which provides a promising way for ultra thin hydrophone array. In this thesis, we investigate the engineering-oriented fiber laser hydrophone techniques according to what we have learned in the research on interferometric fiber hydrophones during the past decades.Our work on fiber laser hydrophone relates to short linear cavity fiber laser, acoustic signal processing, mounting or coating structure design and wavelength division multiplexing （WDM） technique. The effective lasing mode control and laser noise are investigated and we fabricate several linear cavity fiber lasers and their performances are carefully measured. The acoustic response of fiber laser hydrophone is modeled and pressure resolution is analyzed. Phase Generated Carrier （PGC） algorithm is applied to demodulation of multimode fiber laser hydrophone and the abnormal demodulation results are analyzed in detail. A novel mounting structure is designed, which generates enhanced acoustic pressure sensitivity and flat frequency response. The performances of sensing units in WDM array integrated in a single fiber are investigated. The multiplexing capacity is evaluated and crosstalk is measured.The main results of this thesis are as follows:1. The intensity noise models of Er³⁺-doped and Yb³⁺/Er³⁺ co-doped fiber grating lasers are investigated. Relaxation oscillation of laser with Er³⁺-doped fiber exhibits lower frequency and larger amplitude than that of Yb³⁺/Er³⁺ co-doped fiber grating laser, which is confirmed by both theory and experiment.2. The multimode fiber laser hydrophone is modeled and multimode interference is processed using PGC algorithm. By particular design of the optical path difference （OPD） of interrogation interferometer, the multimode fiber laser hydrophone is demodulated correctly and stably.3. A promising fiber laser hydrophone with a novel mounting structure is presented. The acoustic pressure sensitivity is enhanced up to-18dB re Hz/uPa, approaching to the highest reported value; the measured frequency response fluctuation is the least to the best of our knowledge.4. A model to describe the intensity noise of the laser hydrophone in WDM array is established, and the results show that the external injected laser can enhance the intensity noise level, but the relaxation oscillation is not affected, providing a effective method to estimate the actual pump power for each sensing unit in the WDM array.更多还原