Review of the Status and Prospects of Fiber Optic Hydrogen Sensing Technology

With the unprecedented development of green and renewable energy sources, the proportion of clean hydrogen (H2) applications grows rapidly. Since H2 has physicochemical properties of being highly permeable and combustible, high-performance H2 sensors to detect and monitor hydrogen concentration are essential. This review discusses a variety of fiber-optic-based H2 sensor technologies since the year 1984, including: interferometer technology, fiber grating technology, surface plasma resonance (SPR) technology, micro lens technology, evanescent field technology, integrated optical waveguide technology, direct transmission/reflection detection technology, etc. These technologies have been evolving from simply pursuing high sensitivity and low detection limits (LDL) to focusing on multiple performance parameters to match various application demands, such as: high temperature resistance, fast response speed, fast recovery speed, large concentration range, low cross sensitivity, excellent long-term stability, etc. On the basis of palladium (Pd)-sensitive material, alloy metals, catalysts, or nanoparticles are proposed to improve the performance of fiber-optic-based H2 sensors, including gold (Au), silver (Ag), platinum (Pt), zinc oxide (ZnO), titanium oxide (TiO2), tungsten oxide (WO3), Mg70Ti30, polydimethylsiloxane (PDMS), graphene oxide (GO), etc. Various microstructure processes of the side and end of optical fiber H2 sensors are also discussed in this review.