针对分布反馈式(DFB)光纤激光水听器的加速度响应影响声压信号探测的问题，研制了一种聚氨酯端面增敏结构的DFB光纤激光水听器。建立了该结构水听器的加速度灵敏度理论模型，理论分析了套筒结构与水听器的加速度灵敏度的关系，仿真分析了水听器两端聚氨酯的弹性模量、泊松比以及高度的差异与其加速度灵敏度的关系，实现了对水听器各结构以及材料参数的优化，并制作了水听器原型样品与拖曳线列样阵，分别开展了加速度灵敏度测试和湖上动态拖曳实验研究。实验结果表明，该结构水听器在20～2000 Hz频率范围内的加速度灵敏度在各频点均小于1.2 dB，与理论分析结果较为吻合，在动态拖曳过程中的变速运动阶段也能对目标形成较高信噪比的稳定波束指向。水听器的抗加速度性能得到了有效预测以及实验验证。

针对分布反馈式光纤激光水听器在用于水声探测时极易受加速度效应干扰的问题, 设计了一种双膜片对称结构的光纤激光水听器, 对该水听器的抗加速度性能进行了研究.建立了双膜片结构水听器的加速度灵敏度理论模型, 分析了水听器各部件的尺寸大小、材料参量与水听器加速度灵敏度的关系, 实现了对水听器结构的优化设计;加工制作了分布反馈式光纤激光水听器原型样品, 并进行了实验研究.测量结果表明, 在2.5～10 kHz的频率范围内, 该结构水听器的平均声压灵敏度为－132.6 dB, 波动幅度不大于±0.5 dB, 加速度灵敏度小于－28 dB.该水听器在保证了较高声压灵敏度与平坦的响应曲线的同时, 抗加速度性能也得了有效改善, 可大大提高光纤激光水听器阵列在运动状态下对远距离目标探测的信噪比.

为了进一步增大光纤拖曳阵的探测距离, 研制了缆径为16 mm的32元分布反馈式光纤激光水听器拖曳线列阵.阵元在10～2 000 Hz频率范围内的平均声压灵敏度为－142.7 dB(re 1rad/μPa), 波动幅度小于±2 dB.基于声光调制器的时分、波分联合复用技术实现了32元光纤激光水听器的多路复用, 各个阵元之间以及各个通道之间的串扰均小于－40 dB, 并完成了静态和动态拖曳湖上实验.实验结果表明, 研制的32元分布反馈式光纤激光水听器拖曳线列阵无论是在静态, 还是在6～16节的动态拖曳状态, 都能对目标形成稳定的波束指向, 与GPS轨迹记录完全一致, 展现了分布反馈式光纤激光水听器拖曳线列阵在工程上的应用前景.

Rayleigh-back scattering induced coherence collapse of an asymmetric distributed feedback fiber laser (DFB FL) sensor is investigated using a composite cavity model. The coherence collapse threshold condition of the asymmetric DFB FL sensor is measured. The DFB FL sensor shows different dynamic behaviors in different pump configurations. According to the asymmetric behavior to the external optical feedback, a novel method to find the actual phase shift position of the asymmetric DFB FL sensor is presented.

A sensor array system formed by arranging four asymmetric distributed-feedback fiber lasers (DFB-FL) in ascending order according to their slope efficiencies was proposed. The output flatness could be effectively improved with the application of asymmetric DFB-FLs. The last element had almost the same output with the others although it obtained the smallest pump power. The relative intensity noise (RIN) and relaxation oscillation frequency of the sensor array were also analyzed. It is found that the relaxation oscillation frequency of a certain DFB-FL was relevant to its relative position in the array. And the RIN of a certain DFB-FL was always affected by the other elements in the array, which was not dependent on the order of their arrangement.

相移光栅是构成 DFB 光纤激光器谐振腔的关键元件,当相移光栅制作中引入附加损耗时, 耦合系数和光栅长度 对 DFB 光纤激光器最佳输出特性会产生明显影响。采用传输矩阵法,数值分析了不同谐振腔损耗下最佳输出功率 所对应的最佳光栅长度及耦合因子的变化。结果表明,在设计光纤激光器时,根据光纤光栅的制作损耗,优化光栅 长度及耦合因子可以使光纤激光器的输出实现最佳化。这些结论对基于光纤激光器的结构优化具有指导意义。

为了探明分布反馈式(DFB)光纤激光器用于水声探测时,所测得的声压灵敏度高于静压条件下计算所得的声压灵敏度,且动态响应曲线不平坦的原因及其机理,对DFB光纤激光器的动态特性进行了研究。对两端固定并分别置于空气和水介质中的DFB光纤激光器的振动模态进行了数值仿真分析;设计加工了实验夹具,分别对其进行了实验研究。实验测得数据显示,两端固定的裸纤在发生振动时的第一阶固有频率与其夹持长度有关,且随着该长度的增大,固有频率降低;当夹持长度分别为50、55和60 mm时,在空气和水介质中DFB光纤激光器振动的第一阶固有频率分别约为250、200、125 Hz以及200、160、120 Hz,实测数据与仿真分析吻合。结果表明,当DFB光纤激光器受外界激励发生振动时,会引起激光器输出信号幅值的波动,导致其声压灵敏度出现起伏,第一阶固有频率对其具有很大的影响。

At first, we made a approximative λ/4-shifted DFB Yb-doped fiber laser with double exposure method.The length of Yb-doped fiber is 10cm. Secondly, we processed the fiber laser by UV trimming. In addition, the running characteristics of the λ/4 phase-shift DFB Yb3+-doped fiber CW lasers were researched. The fiber laser have thefollowing excellent characteristics: Output power of 25 mW, fluctuation of less than 2%, 100% single longitudinal mode,27 dB polarization extinction ratio, 60 dB signal-to-noise. What is more, the effect on the fiber lasers is also researched from several factors such as temperature, mechanism perturbation and fresnel reflection of fiber end section.

The running characteristics of the single longitudinal mode, single polarization λ/4 phase-shift DFB Yb3+ -doped fiber CW lasers were researched. The fiber laser have the following excellent-characteristics: Output power of 25 mW, fluctuation of less than 2%, 100% single longitudinal mode, 30 dB polarization extinction ratio, 60 dB signal-to-noise. On the other hand, the effect on the fiber lasers is also researched from several factors such as temperature, mechanism perturbation and fresnel reflection of fiber end section.

An approximative λ/4 -shifted DFB Yb-doped fiber laser was made in the length of 10 cm Yb-doped fiber by double exposure method. Then, it was treated with λ/4-shifted Yb-doped DFB fiber laser with UV trimming. The running characteristic of the laser with scaning F-P interferometer and oscilloscope was observated. SLM Yb-doped λ/4-shifted DFB fiber laser was obtained. The threshold is 20 mW. When pump power was 130 mW. 25 mW SLM laser at 1053 nm was got.