A Transverse Load Sensor With Ultra-Sensitivity Employing Vernier-Effect Improved Parallel-Structured Fiber-Optic Fabry-Perot Interferometer

The parallel structured fiber-optic Fabry-Perot interferometer (FPI) is theoretically proposed and experimentally demonstrated for transverse load measurement based on Vernier-effect. This kind of sensor consists of a hollow microsphere cavity fiber-optic FPI for sensing function and an air cavity for reference, both of which are parallel connected by a 3 dB optical fiber coupler with the functionality of Vernier-effect. Experimental results indicate that the proposed sensor can provide a high transverse load sensitivity of -3.75 nm/N, which is 3.4 times higher than single hollow microsphere cavity FPI. Moreover, with the excellent features of low cost, easy fabrication, and stable sensing, the parallel structured FPIs proposed will provide a new vision for high sensitivity transverse load sensing.