Torsion, Refractive Index, and Temperature Sensors Based on An Improved Helical Long Period Fiber Grating

Abstract

The sensors measuring torsion, refractive index, and temperature are demonstrated, based on an improved helical long-period fiber gratings (HLPFG), in which the refractive-index and torsion sensitivity were significantly enhanced by reducing the grating diameter. This was achieved using the velocity difference between two translational stages as the optical fiber was heated by a hydrogen-oxygen flame. As the grating diameter decreases from 109 to 85 μm, the sensor's refractive-index sensitivity at RI of 1.444 increases from -1210.20 to -3133.80 nm/RIU, and torsion sensitivity was enhanced from -245.80 to -942.77 nm/(rad/mm), respectively. Moreover, the sensor's temperature sensitivity was measured to be about 77.17 pm/°C. Hence, such a sensor based on improved HLPFG could have great potential in sensing applications.