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 LPGs having a reduced fiber diameter fabricated by tapering or etching processes. At the same time, the MCFs provide good versatility for multi-channel sensing and monitoring applications. In the experiment, we achieved both torsion direction recognition and torsion measurement with sensitivity as high as 0.966 nm/(rad/m) and -1.017 nm (rad/m) in clockwise and counterclockwise directions, respectively, and we also observed good linear responses to strain and temperature. The proposed AO-LPG inscribed in MCF has good potential in multi-channel multi-parameter sensing applications.