H2 sensing performance of optical fibers coated with WO3 film

Optical gas sensing performance of optical fibers coated with sputtered Pd/WO3 films was investigated for low concentration H2 sensing. This optical fiber H2 sensor was prepared by RF sputtering of WO3 on the tip of the multimode fiber at 260°C and subsequently depositing a Pd catalytic layer. Highly uniform nanotextured film, with individual crystallites having diameters in the range of 35-50 nm was observed. The sensing mechanism was based on the reflectance change of Pd/WO3 layers towards H2 reliant on the gasochromic effect. Under the conditions of different sensing layer thicknesses and different operating temperatures, full Vis-NIR spectra investigations were carried out during the sensor testing. It was found that the optical fiber H2 sensor coated with Pd/WO3 film show a remarkable optical reflectance response towards H2 concentrations as low as 0.06%. The optimum sensing layer thickness was 200 nm and the optimum operating temperature was found to be 100°C.