Fiber laser with built-in FBG and LPFG for simultaneous two parameters sensing

This work aims to measure the liquid level and temperature at the same time. We propose a fiber laser based on Bragg grating (FBG) and a long-period fiber grating (LPFG) for simultaneously two-parameter sensing. It has one wavelength peak induced by the FBG and one central dip induced by the LPFG. The resulting temperature varies from 25 degrees C to 50 degrees C in 7.5 nm wavelength drifts of LPFG with linearity R (2) of 0.9994. The sensitivity of the FBG liquid level sensing will be affected by the temperature change, ranging from-0.12 nm cm(-1) at low temperature to-0.004 nm cm(-1) at high temperature, and the linearity R (2) is about 0.9967. Thanks to the laser cavity, the proposed fiber laser with an extensive dynamic range could be used for remote monitoring.