Hydrogen sensor based on polymer-filled hollow core fiber with Pt-loaded WO3/SiO2 coating

A simple, compact and highly sensitive hydrogen sensing device based on a polymer-filled hollow core fiber coated with Pt-loaded WO3/SiO2is demonstrated. The device is composed of a tiny segment of hollow core fiber (HCF) spliced to a standard single mode fiber (SMF) incorporated with a fiber Bragg grating (FBG). The HCF is filled with polymer and the inner air-gap near the interface between SMF and polymer forms a micro-cavity Fabry-Pérot interferometer (FPI). With Pt-loaded WO3/SiO2 coating acting as the catalytic layer, hydrogen undergoes an exothermic reaction with oxygen in air and releases heat when the device is exposed to hydrogen, which induces local temperature change of FPI and hence leads to reflection spectrum shift of the proposed device. Here, the FBG is used to compensate the surrounding temperature effect and eliminate the temperature cross-sensitivity of the device. A wavelength shift of over 35 nm is obtained with a 242-μm-long polymer-filled HCF for 4% (vol%) H2 concentration, and the maximum sensitivity of 17.48 nm/% (vol%) H2 is achieved within the range of 0-4.0% (vol%) H2 in air. The sensor device also exhibits fast response time to hydrogen.