高灵敏度甚低频光纤水声传感结构、机理及噪声抑制研究

Very-low frequency (VLF) optical fiber underwater acoustic sensing (OFUAS) is important to many applications such as underwater target detection, ocean dynamic environment research, global climate monitoring and ocean disaster warning. However, there are only very few researches focused on high-sensitive and low-noise OFUAS. In view of currently existed fundamental bottleneck problems in OFUAS such as ambiguity of sensing mechanism and relatively large noise, this project will concentrate on a series of research proposals including underwater operation mechanism of optical fiber extrinsic Fabry-Perot interferometric (EFPI) underwater acoustic sensor (UAS) based on micro-structured diaphragm, design of underwater VLF acoustic sensing micro-structure, photoelectric signal recovery in VLF range, mechanism of noise generation, transmission and conversion, noise suppression. Several key technologies will be broken through which consists of optimal design of high-sensing structure under strong multiphysics coupling, joint signal detection of white-light path-matched differential interferometric homodyne phase demodulation and gap length demodulation based on parameter matching in optical spectrum domain, principal component analysis of system noise based on the correlation in frequency domain and experiments thereof, etc. Meanwhile, the sensing mechanism of the sensitive micro-structure in the enclosed hydrostatic-pressure-resistant liquid-filled cavity is clarified. And then the transmission and conversion regularity of the quantum fluctuation noise and the thermodynamic noise is obtained. Besides, the noise suppression method based on the strap-down noise cancellation of the opto-electric hardware and the signal processing software will be established. Furthermore, a sample principle device of the VLF detection system with self-calibration and self-compensation for optical fiber EFPI UAS will be developed. As a result, the outcome of the project will provide basic support for the improvement of VLF underwater acoustic sensing ability, as well as the development of VLF optical fiber underwater acoustic detection.

甚低频水声检测在水下目标探测、海洋动力环境研究、全球气候监测和海洋灾害预警等领域凸显出重要应用价值，而目前国内外对甚低频光纤水声传感的研究极为匮乏。课题针对光纤水声传感在甚低频段存在的传感机理不清、噪声偏大等基础瓶颈问题，重点开展EFPI传感器甚低频水下工作机理、甚低频声传感微结构设计、甚低频光电信号检测、噪声产生与作用机制和抑制方法等方面的研究，突破多物理场强耦合下高灵敏度传感结构优化设计、白光路径匹配零差相位解调与光谱参数匹配腔长解调联合信号检测、基于频域相关特性的噪声主成分分析与试验等关键技术，掌握耐压封闭液腔中敏感微结构膜片甚低频水声信号传感机理，获得量子涨落和热动力噪声的传递和转化规律，建立基于光电硬件和信号处理算法的软硬件捷联对消噪声抑制方法，形成光纤EFPI水声传感器自校准自补偿甚低频检测原理装置。项目将为提升对甚低频声波的感知能力、发展甚低频光纤水声探测系统提供基础支撑。

项目针对当前光纤水声传感在甚低频段存在的传感机理不清、噪声偏大等基础瓶颈问题，开展了基于微结构膜片的光纤EFPI水声传感器甚低频水下工作机理、水下甚低频声波传感微结构设计、甚低频光电信号检测、噪声产生与作用机制和噪声抑制方法等方面的研究。研究期间，项目突破多物理场强耦合下传感结构优化设计、白光路径匹配零差相位解调与光谱参数匹配腔长解调联合信号检测、基于频域相关特性的噪声主成分分析与试验等关键技术，掌握了封闭液腔中敏感微结构膜片甚低频水声信号传感机理，获得了量子涨落和热动力噪声的传递和转化规律，建立了基于光电硬件和信号处理算法的软硬件捷联对消噪声抑制方法，形成了光纤EFPI水声传感器自校准自补偿甚低频检测系统基础原理装置。项目的研究成果可为提升对甚低频声波的感知能力、发展甚低频光纤水声探测系统提供基础支撑。