光纤MEMS高精度相对重力测量研究

High precision gravity measurement has wide application requirements in seafloor observation, oil and gas exploration, underground space exploration and gravity aided inertial navigation. The current domestic and foreign precision gravity measurement issues and the status of optical fiber MEMS sensing mechanism are studied. Based on the laboratory achievements on gravity measurements and MEMS independent development, this project proposes a new principle and technology of relative gravity measurement. It has a very low frequency MEMS relative gravity sensing structure and optical fiber composite interference for displacement correlation measurement. To optimize the design of a MEMS silicon-based spring of relative gravity sensing mechanism, the target natural frequency will be lower than 2Hz. On the other hand, sensitive mass displacement detection uses optical fiber interference correlation detection method. The whole header detector is carried out vacuum packaging and temperature control. It is expected to improve the optical fiber MEMS high precision detection mechanism and evaluation mechanism for relative gravity, and achieve high sensitivity better than 1μGal/√Hz. We are hoping to reach even overtake western countries of the precise relative gravity signal detection level, adapt to the development situation of China's national economy, and meet the urgent needs of the construction of the national security strategy.

高精度重力测量在海底观测、油气和矿藏勘探、地下空间勘察及重力场辅助导航等方面有着广泛的应用需求。针对目前国内外精密重力测量存在的问题，综合光纤MEMS传感机制的研究现状，本申请拟在实验室前期重力测量仪器研制和MEMS自主开发的基础上，提出基于极低固有频率的MEMS相对重力传感结构与光纤多路干涉型微位移相关检测相结合的高精度相对重力测量新原理和技术。一方面对硅基挠性相对重力传感机构中的弹簧-质量系统进行优化设计，其目标固有频率将低于2Hz；另一方面，采用光纤多路干涉相关检测法实现敏感质量块微位移检测，并对表头整体进行真空封装和温度控制，有望完善光纤MEMS高精度检测相对重力的机理、方法以及评估机制，实现灵敏度优于1μGal/√Hz的高精度相对重力检测，希望能达到甚至“弯道超车”西方国家现有精密相对重力信号检测水平，适应我国国民经济发展形势的需要，满足国家战略安全建设需求。

本课题结合光纤和MEMS传感技术进行微弱加速度信号测量，围绕传感信号的提取机制与光纤多路干涉相对重力传感模型的建立、正负刚度弹簧调节微机械结构系统固有频率理论分析与实践验证、高灵敏度加速度测量噪声水平评估方法等研究内容开展研究，并进一步固化光纤MEMS加速度计的加工、集成工艺和测试方法，以及光纤干涉法加速度测量性能改善等方面开展相关技术研究。经过性能评估证明，该光纤MEMS加速度测量噪声水平达到2.4ng/√Hz @10Hz，灵敏度3165V/g；其中，光学位移检测噪声水平达到了208fm/√Hz @10Hz。该技术可衍生光纤MEMS微震仪、光纤MEMS星载微震仪等，可广泛应用于高空间分辨率的重力场导航、矿产资源勘探以及地球物理科学基础研究等领域。