High Sensitive Directional Torsion Sensor Based on a Segmented Long-Period Fiber Grating

A segmented long period fiber grating (LPFG)-based torsion sensor with both high sensitivity and ability to discriminate torsion direction is proposed and experimentally investigated. The sensor is made up of three spatial orthogonal short LPFGs by using a CO2 laser notched method. Experimental results show that the torsion sensitivities can reach -0.54 and 0.33 dB/(rad/ m) in dip depth and 0.30 and -0.14 nm/(rad/m) in resonance wavelength for clockwise and counterclockwise, respectively, in a single polarization state. Torsion rate and torsion direction can be measured simultaneously by the sensor. Moreover, the temperature sensitivity of the sensor has been determined as 0.067 nm/degrees C. Therefore, the proposed segmented-LPFG would have great potential applications in engineering and fiber sensors.