Fiber-Optic Hydrogen Sensors: A Review

Optical fiber hydrogen sensor has become a research hotspot once proposed, since its unique properties of intrinsic safety. In the past three decades, varieties of optical fiber hydrogen sensors have been proposed, which could be categorized into five types, including interference type, micromirror type, evanescent field type, surface plasmon resonance type, and fiber Bragg grating type. This review focuses on the representative of the above five types of hydrogen sensors, based on Pd alloy or/and WO
₃
sensitive materials. Whereas, their structures, characteristics, and sensing performances are critically overviewed.