基于非对称法布里-珀罗干涉的微位移光纤传感机理及应用研究

Micro-displacement sensor with high resolution and wide dynamic range is key component of high-resolution relative gravimeter, thus being of great strategic significance for deep earth resource exploration of China. Conventional extrinsic optical fiber Fabry-Perot (F-P) interferometer based micro-displacement sensors have attracted broad attention and applications, but the problem that high resolution is contradictory with wide dynamic range still remains to be solved. This project plans to conduct study on the enhanced interaction mechanism between the in-plane micro-displacement and optical field of the asymmetrical F-P interferometer, the method for improving Q-factor of the asymmetrical F-P cavity, and the algorithm for common mode noise suppression. We will explore the sensing mechanism of micro-displacement optic sensor based on an asymmetrical F-P interferometer. By fabricating a step-shaped external reflector which is asymmetrical in plane and combining it with the fiber flat-end, an asymmetrical F-P interferometer containing dual frequency can be formed. By introducing the optical Vernier effect magnification mechanism, and adopting light intensity difference demodulation algorithm to suppress common mode noise, the high-resolution micro-displacement detection is expected to achieve. Meanwhile, by measuring the in-plane micro-displacement of the step-shaped reflector, the wide dynamic range is expected to achieve. The final goal is to realize the in-plane micro-displacement fiber optic sensing with resolution of 0.1nm and dynamics range of ±10μm, meeting the application requirement in the field of deep earth resource exploration.

高精度、大动态范围的微位移传感器是高精度相对重力仪的重要单元，对于我国深地资源勘探具有重要的战略意义。非本征光纤法布里-珀罗（Fabry-Perot，F-P）干涉型微位移传感得到广泛的关注和应用，但是高精度和大动态范围相制约的问题一直面临挑战。本项目拟对面内微位移与非对称F-P干涉光场的耦合增强机理、非对称F-P腔Q值提升方法、传感系统共模噪声抑制方法三个关键科学问题开展研究。探索基于非对称F-P干涉的微位移光学传感机理，通过制备面内不对称的阶梯型反射腔面，与光纤端面构成双频非对称F-P干涉结构：引入光学游标效应放大机制，采用光强差分解调方法抑制共模噪声，实现高精度微位移检测；同时，测量阶梯型反射腔面的面内微位移，提升微位移检测动态范围。最终目标是实现精度0.1nm、动态范围±10μm的面内微位移光纤传感，满足深地资源勘探等领域的应用需求。

位移是是基本物理参数之一，高精度位移测量在基础科学研究和工业生产中的各个领域都有重要应用。非本征光纤法布里-珀罗（F-P）干涉结构具有精度高、结构紧凑、制备简单和环境适应性强的优点，在位移传感领域受到广泛关注，但其高精度和大动态范围相制约的问题一直面临挑战。本项目提出一种面内不对称的阶梯型反射腔面，与光纤端面构成非对称光纤F-P干涉结构，进一步采用光强差分解调方法抑制共模噪声，实现了高精度和大动态范围兼顾的位移测量。.本项目建立了面内位移与非对称光纤F-P干涉光场的耦合理论模型，分析了关键参量对位移传感灵敏度和精度的影响，确定了反射率和阶梯型反射腔面阶梯高度等结构参数的取值；采用MEMS工艺制备阶梯型反射面，选取顶硅层厚度为50μm的绝缘体上硅片作为基底、厚度为300nm的铝膜作为反射薄膜，通过优化“匀光刻胶-曝光显影-深反应离子刻蚀-镀铝薄膜-显微观测”工艺流程的关键参数，制备得到了台阶高度50μm、反射率90%的阶梯型反射面；设计了高精度解调方案，采用角频率傅里叶变换法分析非对称F-P干涉结构的光谱，提出了共模抑制降噪的面内位移提取方法，实现了非对称F-P干涉面内位移传感的高精度解调；搭建了面内位移传感实验平台，实验研究了非对称F-P干涉结构的面内位移传感特性，结果表明非对称F-P干涉光纤位移传感器可实现精度0.1nm/√Hz @ 100Hz，测量范围±10μm，分辨率优于5nm的面内位移测量，达到项目申请时的预期指标。.此外，本项目还分析了非对称F-P干涉结构的面内位移与面外位移耦合关系，提出了二维位移解耦方案，开展了二维随机位移测量实验，结果表明面内与面外位移的绝对测量误差均在±0.1μm范围内，实验结果与理论分析相符，证明非对称F-P干涉结构可用于高精度二维位移测量。.基于以上工作，共发表SCI论文2篇，项目负责人均为第一或者通讯作者，申请国家发明专利4项，授权2项。依托此项目，培养硕士研究生2人，博士研究生2人。本项目所获成果，将对光纤位移传感领域的发展产生积极作用。