Power-interrogated and simultaneous measurement of temperature and torsion using paired helical long-period fiber gratings with opposite helicities

A power-interrogated sensor which allows for simultaneous measurement of temperature and torsion is proposed and experimentally demonstrated, which is based on utilization of paired helical long-period fiber gratings (HLPG) with opposite helicities. Unlike most of the previous fiber grating-based sensing system, here the paired HLPGs are simultaneously used as both the sensing and the interrogating elements and thus the bulk and high-cost wavelength-interrogating device can be eliminated. Moreover not only the torsion but also the torsion direction can be determined simultaneously. The temperature sensitivity obtained is estimated to be similar to 41 pm/degrees C within a range of 20-150 degrees C, and the torsion responsivities obtained are similar to-1.414 nm/rad/m and similar to 1.276 nm/rad/m, respectively within a rotation angle of -360 degrees similar to 360 degrees. (C) 2014 Optical Society of America