Compact Torsion Sensor With High Sensitivity Using Angle-Offset Long Period Grating Inscribed in Multicore Fiber

We proposed a compact torsion sensor with high sensitivity using angle-offset long period grating (AO-LPG) inscribed in multicore fiber (MCF). AO-LPGs can be conveniently fabricated on the outer cores of MCF by heating and periodically rotating the MCF using a commercially available fusion splicer without obvious degradation in mechanical strength compared with long period gratings (LPGs) having a reduced fiber diameter fabricated by tapering or etching processes. At the same time, the MCFs provide good versatility for multichannel sensing and monitoring applications. In the experiment, we achieved both torsion direction recognition and torsion measurement with sensitivity as high as 0.966 and −1.017 nm/(rad/m) in clockwise (CW) and counterclockwise (CCW) directions, respectively, and we also observed good linear responses to strain and temperature. The proposed AO-LPG inscribed in MCF has good potential in multichannel multiparameter sensing applications.