Sensitivity-Enhanced LPFG Bending Sensor Induced by Tapering Coupled Region

In this letter, a sensitivity-enhanced bending sensor induced by tapering coupled region is proposed and experimentally tested. The sensor is consisted by tapered multi-mode fiber (MMF) embedded single mode-no core-single mode fiber structure. The large core mismatch and the tapered structure excites the higher-order cladding modes, which significantly enhances the bending sensitivity of the sensor. Experimental results present that the bending sensitivity of the structure with 3 periods of tapered MMF reaches −42.31 nm/m−1 and −45.93 nm/m−1 for Dip-A (1323.4 nm) and Dip-B (1548.8 nm), respectively. In addition, the simultaneous measurements of bending and temperature can be realized. With properties of simple structure, high sensitivity and compact volume, the designed sensor provides a fresh thinking to solve the problem of bending measurement.