Torsion, Strain, and Temperature Sensor Based on Helical Long-Period Fiber Gratings

A novel fiber sensor, which enables us to simultaneously measure the torsion, strain, and temperature, is proposed and experimentally demonstrated, which is based on utilization of two successively cascaded helical long-period fiber gratings (TSC-HLPGs). By using the proposed approach, crosstalk effects among temperature, strain, and torsion can totally be discriminated for the first time to the best of our knowledge. Moreover, not only the torsion angle, but also the torsion direction can be determined simultaneously. Accuracies for the resolved temperature, the strain, and the torsion angle are estimated to be similar to 0.8 degrees C within the range of 20 degrees C-100 degrees C, similar to 225 mu epsilon within the range of 0-2600 mu epsilon, and similar to 1.2 degrees (corresponding to a torsion responsivity of 3.54 nm/rad/m in our case) within the rotation angle of -360 degrees similar to 360 degrees, respectively.