基于光学微腔的高精度水下声场无源感知关键技术研究

This project is aiming at the urgency demand for national maritime security and resource surveying, mainly focused on the study of new theory of underwater acoustic sensing assisted by optical fibers and exploration of novel technology for transduction between acoustics and optics, combined with innovative structure optical amplification technology as well as signal interrogation and analytical processing technology. The project strives to achieve broadband underwater acoustic detection with high precision and large-capacity multiplexing. The micro-cavity formed by optical fibers and two-dimensional (2D) graphene photonic crystal diaphragm is able to achieve highly sensitive acoustic sensing. With the help of optical phase magnification and extraction from ripple spectrum based on self-fitting method, the acoustic signal can be interrogated with high precision. The polydomain multiplexing and fiber sensor networking technology gives rise to the capacity of the underwater acoustic detection. Packaging and noise cancellation techniques of acoustic sensing unit will also be investigated. The major innovation points of the project include novel mechanism of transduction between acoustics and optics, phase magnifying and demodulation technology, optical micro-cavity polydomain multiplexing and networking. Research results with internationally influence are expected to be achieved in these areas. The achievements of this project can be applied in detecting thousands of meters deep marine acoustic parameters .The technologies proposed by our project can adapt to the harsh environments in the ocean and have the advantages of immune to electro-magnetic interference, high sensitivity, and potential in applications of long distance with large capacity. The project has important application prospect in marine resource detection, construction of underwater monitoring system and advanced water sound equipment.

本项目面向国家海洋安全与海洋资源监测的迫切需求，研究水下声场光纤传感的新理论与新方法，探索声光换能的新技术与新工艺，结合创新结构光学放大技术、信号解调分析与处理技术,力争实现高精度、多域复用、宽频段的水下声场探测。项目基于光纤-石墨烯二维光子晶体薄膜构造的光学微腔，可实现声信号的高灵敏感知；结合声场相位光学放大以及光谱自拟合与相位提取的创新解调技术，可实现宽频水声信号高精度获取；采用多域复用光纤传感组网技术可有效提高水声传感容量；另外本项目将研究水声传感单元封装、降噪等技术。项目主要创新点包括：声光换能新机理与新方法、相位放大与解调创新技术、光学微腔多域复用组网技术，预期在这些方面将取得具有国际影响力的研究成果。本项目研究成果可探测数千米海洋环境水声参数，适应海洋恶劣环境、抗电磁干扰、灵敏度高、易于大容量长距离应用，在海洋资源探测、构建水下监测系统、先进水声装备等方向具有重要的应用前景。

项目完成了基于光学微腔方案的高精度水下声场无源感知技术的研究。主要内容包括：1）研究了基于光纤非本征法布里-珀罗干涉仪（Extrinsic Fabry-Perot Interferometer，EFPI）的声波传感器，包括传感器传感薄膜的选择与制备以及传感器结构的设计和制作，实现了宽频带，高灵敏，低噪声的水下声场响应。传感器可实现0.1Hz~20 kHz的宽频响应，具有增敏结构的传感器最小可探测声压(Minimum Detectable Pressure, MDP)可达 13.6 μPa/√Hz @ 1000 Hz；2）研究了高精度声波解调算法及信号放大技术，其中基于白光干涉（White light interferometry, WLI）的相位解调算法可以同时解调多个微腔型传感器且具有光学相位增敏能力；基于直线拟合-三角恒等变换-微分交叉相乘（Linear Fitting Trigonometric Identity Transformation Differential Cross Multiplication，LF-TIT-DCM）的双波长相位解调算法可以降低环境干扰的影响且能够解调更宽频率更大动态范围的声波信号；所提出的声波解调算法弥补了目前常用相位解调方法的缺点，提高了传感器的声场探测精度；3）研究了光学微腔型传感器的复用成阵技术，提出了一种基于光开关和耦合器的时分/频分多域复用技术，结合所研究的复用传感器相位解调算法，完成了传感器阵列的信号收集与分析，采用多重信号分类（Multiple Signal Classification，MUSIC）算法实现了声源定位。4）最后，本项目研究了光学微腔型水听器的封装技术，实现了耐深海静水压力和耐腐蚀的水听器封装设计与测试。此外，本项目还研究了光探声场的辅助技术，包括激光光源的研究，深海温度与传感结构应力感知方法的研究等，提高了探测系统的稳定性与准确性，保证了声场探测的精度。总的来说，本项目研究的高精度水下声场无源感知技术能适应海洋恶劣环境，具有抗电磁干扰、灵敏度高、噪声低、易于大容量长距离复用组网的优势，在海洋资源探测、构建水下监测系统、先进水声装备等方向具有重要的应用前景。.项目共计发表论文17篇，其中期刊论文16篇，会议论文1篇；会议特邀报告12次；申请专利16项，其中授权7项；授权2项软件著作权。