Improved Performance of Fiber Bragg Hydrogen Sensors Assisted by Controllable Optical Heating System

A novel fiber Bragg grating (FBG) hydrogen sensor based on the Pd/Ni composite film and controllable laser heating system is proposed and demonstrated with enhanced sensitivity. The Pd/Ni composite film was sputtered around the greatly etched FBG, and the atomic ratio of Pd and Ni was controlled at 91:9 during the sputtering process. A 980-nm pump laser and proportion integration differentiation controller are employed to induce heating in the Pd/Ni composite film. Experimental results show that the stability of the hydrogen sensor is significantly improved with ±1 pm fluctuation at 1% hydrogen concentration. In addition, the proposed sensor exhibits higher sensitivity and quicker response rate during hydrogen exposure.