Performance-enhanced optical fiber hydrogen sensors based on WO_3-Pd_2Pt- Pt composite film with controlled optical heating

摘要

A novel fiber Bragg grating (FBG) hydrogen sensor based on WO3-Pd2Pt-Pt composite film and controllable laser heating system is proposed and experimentally demonstrated with improved performance. The hydrogen sensor is a small stainless steel tube with two gas holes. The stainless steel tube contains two single mode fibers. One is inscribed with two short-period FBGs for monitoring the hydrogen concentration and ambient temperature, and the other is linked with 980 nm laser for optical heating. The proportion integration differentiation (PID) controller is employed to adjust the out-put power of 980 nm laser during heating process. Experiments demonstrate that the stability of the hydrogen sensor is significantly improved with 2.8% fluctuation at low hydrogen concentration. In addition, the relative standard deviation of the proposed sensor after optical heating decreases to a quarter of that before optical heating, which is only 1.1%. The hydrogen sensor also exhibits high sensitivity and quick response rate during hydrogen exposure, which is beneficial to monitor low concentration hydrogen in real time.