All fiber Fabry–Pérot interferometer for high-sensitive micro-displacement sensing

A fiber-optic displacement sensor based on Fabry–Perot interferometer (FPI) with high sensitivity is investigated in both numerical simulation and experiment. The end faces of two fiber tips are applied as the mirrors to compose the Fabry–Perot cavity (FPC). The variable lengths of the FPC will introduce different fringe spacings (FS) of the FPI transmission spectrum. With respect to this characteristic, the micro-displacement can be sensed by the FS of the transmission spectrum. Maximum sensitivity of 56.6 nm/μm, which is much higher than the previous fiber sensors, has been achieved experimentally. Due to the advantages of extremely simple configuration and manufacturing operation, the sensor is significantly beneficial to practical application.