Fast Response and Highly Repeatable Hydrogen Measurement via Pd/WO3 Film Coated Optical Fiber Sensors and Spectral Comb Interrogation

Abstract

Hydrogen, a high-density and clean energy, have been widely used in various critical applications. However, the safety risk caused by hydrogen leakage during storage and transportation is still a non-negligible issue. Therefore, it is necessary to offer hydrogen sensors with fast response and high repeatability, and it will be perfect for achieving in situ monitoring over the lifecycle of hydrogen production and utilization. Here we proposed a compact optical fiber sensor with a short section of tilted Bragg fiber grating (TFBG) inscribed in the fiber core and coating the fiber surface with a 40 nm thickness of palladium and tungsten trioxide (Pd/WO3) combined film. The TFBG excites tens of narrow cladding resonances, part of which possess refractive indexes matching that of the Pd/WO3 coating and provides a high sensitivity to the surrounding hydrogen concentration change. The sensor offers improved sensing characteristics, including a fast response time (less than 10 seconds), high repeatability (over tens of measurements), an excellent linear response (higher than 99.6%) over the 0 to 3% concentration range, with a detection limit of approximately 2417 ppm.