Tip hydrogen sensor based on liquid-filled in-fiber Fabry–Pérot interferometer with Pt-loaded WO3 coating

Abstract

A probe optical fiber hydrogen sensor based on an in-fiber Fabry–Pérot interferometer (FPI) is proposed and experimentally demonstrated. The interferometer consists of a micro-cavity which is filled with thermosensitive liquid and lateral surface coated with hydrogen-sensitive material of Pt-loaded WO3. When the sensor is exposed to the hydrogen environment, the refractive index of the liquid in the cavity changes, and then the reflection spectrum of the FPI shifts due to the exothermal reactions between the hydrogen and WO3 in air with the presence of oxygen and the help of catalyst Pt. By detecting the wavelength shift, the hydrogen concentration can be measured accurately. Experimental results show that the proposed sensor has a high hydrogen sensitivity within a range from 0 to 4.0% (vol.%) and a short response time. Moreover, it exhibits many distinct advantages, such as a tip structure with compact size (<100 μm in total dimension), good repeatability and selectivity to hydrogen and immunity to humidity. All these features reveal that the proposed sensor is promising in the fields of hydrogen leaks or concentration measurement in a narrow space.