【作者】 宋章启；

【导师】 胡永明；

【作者基本信息】 国防科学技术大学 ， 光学工程， 2007， 博士

【摘要】 在Sagnac干涉仪中不需要考虑相位衰落和光源相位噪声问题,偏振衰落问题也可通过在干涉仪中插入Lyot退偏器的方法得到很好解决,因此基于Sagnac干涉仪的光纤水听器与基于Mach-Zehder(MZ)干涉仪的光纤水听器相比有其独特优势。本论文以探索适用于声信号测量的Sagnac光纤传感阵列技术为目标,首先综合分析了Sagnac干涉仪对声信号的响应特性和阵列情况下影响Sagnac光纤水听器传感性能的主要因素。针对Sagnac光纤水听器阵列信号处理,折叠结构的时分复用和噪声光脉冲抑制等关键技术进行了理论和实验研究。提出了双折叠结构Sagnac光纤传感阵列方案,并对其中的信号串扰问题进行了深入研究,制作了动态范围达173dB的Sagnac光纤传感实验系统。本论文完成了国内首条四基元Sagnac光纤水听器阵列,并在此基础上进行了声信号/角速度双参量同阵列测量的验证实验。本论文的主要研究成果和创新如下:1、提出了适用于双折叠结构Sagnac光纤传感阵列的交替相位偏置信号处理方案,降低了对光源稳定性的要求,消除了光源和探测电路引入的低频噪声,并可对非互易相位漂移进行测量和实时补偿。2、针对折叠结构Sagnac光纤传感阵列提出了基于主动相位偏置的时分复用方案,实现了信号光脉冲与噪声光脉冲的分离。发现并从理论上解释了折叠结构Sagnac干涉仪中使用正交共轭镜(法拉第旋转镜)引起干涉信号发生稳定π相移的现象,实现了小信号情况下的噪声光脉冲抑制。3、提出了具备大动态范围调节能力的双折叠Sagnac光纤水听器阵列方案,分析了双折叠结构中的信号串扰问题,研制了实验验证系统,实验测试表明该系统动态范围可达173dB。4、提出了在阵列情况下,进行声信号/角速度双参量测量的概念,并完成了原理性实验;该传感方式可以为光纤水听器拖曳阵的阵形估计和岸基阵的安全预警提供新的传感手段。更多还原

【Abstract】 The fiber-optic hydrophone array based on Sagnac interferometers presents several advantages over the acoustic sensor array based on Mach-Zehnder (MZ) interferometers. The former is insensitive to signal fading and source phase noise and can be easily desensitized to polarization fading just by inserting a Lyot depolarizer in the interferometer.This dissertation presents our efforts to develop the key technologies of Sagnac based sensor array (SSA) for acoustic sensing. The acoustic response characteristics in the Sagnac interferometer and the main factors that may limit the performances of the SSA are analyzed. The signal processing, Time-Division Multiplexing and anti-noise-pulses-overlap in the folded Sagnac sensor array (FSSA) are proposed and demonstrated. The dynamic range and crosstalk are analyzed in the double folded SSA (DFSSA), and a DFSI with 173dB dynamic range is presented. A 4-sensor SSA is developed first time in China, and the possibility of using the SSA as an acoustic/rotation sensor in the same array is demonstrated by experiments.The main innovations and creative points in the dissertation are as follows:1. It proposes a signal processing technique with alternative phase bias in the DFSSA. With this technique, the requirement of stability of optical power can be decreased, the phase drift induced by non-reciprocity can be measured and compensated, and the low-frequency noise due to the detection system and the optical source can be reduced obviously in the output signal.2. It proposes a time division-multiplexing (TDM) scheme, which is compatible with the active phase bias technique mentioned above, to avoid the overlapping of the signal and noise pulses in the FSSA. A stableπphase bias is observed and accounted in the FSSA incorporating an orthoconjugate reflector (Faraday rotator mirror), which can be used to eliminate the optical noise pulses under small signal situation.3. It proposes a double folded Sagnac hydrophone array whose dynamic range is adjustable, and analyzes the crosstalk effects. A DFSI with about 173dB dynamic range is demonstrated experimentally.4. It proposes and demonstrates experimentally the concept of using the SSA as an acoustic/rotation sensor with the same array. This technology can be used in fiber-optic towed array for the shape measurement and in the bottom-mounted array for security.更多还原