A Unit Volume Sensitivity Optimized Optical Fiber Displacement Sensor With Multihinge Lever Symmetrical Structure

Optical fiber Fabry-Perot (F-P) sensor is a high-sensitivity sensor based on fiber-optic sensing and interference principle, which can be used in sensing of displacement, stress, strain, temperature, and so on. In this article, we propose an optical fiber F-P displacement sensor based on a flexible hinge structure, and develop a compact microsized displacement sensor with high sensitivity to measure microdisplacement, with a size of $15\times 10\times 2.4$ mm3. On the basis of mathematical model, we used an optimization algorithm to globally optimize the displacement sensitivity and obtained the optimal dimensional parameters of the sensor structure. We used ANSYS to simulate and analyze our sensor, and the results were basically consistent with the theoretical results. Then, we encapsulated and pasted the F-P cavity with a small-diameter glass capillary, and the F-P was fabricated with an optical fiber at one end and a fiber Bragg grating (FBG) for temperature measurement at the other end. The final experimental tests showed that the sensor had good linearity and displacement sensitivity can reach up to 64 100 pm/mm. The temperature sensitivity is 10.04 pm/°C for FBG and 33.04 pm/°C for F-P.