A fiber-optic evanescent-wave hydrogen gas sensor using palladium-supported tungsten oxide

A new optical-fiber hydrogen sensor has been developed. The sensor utilizes the absorption change of the evanescent field in the clad region. The plat inum- or palladium-supported tungsten oxide was used as sensing media. Two different approaches were adopted for the fiber fabrication. One used Pd/WO 3 containing silicone resin as the clad. The other utilized the sol-gel pro cess to form a thin Pd/WO3 clad. In the presence of hydrogen, strong evanes cent-wave absorption was observed as a result of the formation of tungsten bronze. The sensor sensitively and immediately responded to hydrogen. It wa s found that the characteristics of the sensor were easily controlled by th e amount of catalysts. The sensor developed in this study has potential to measure the spatial distribution along the fiber line, unlike the tradition al hydrogen sensors that measure the concentration of a certain spatial poi nt. (C) 2000 Elsevier Science S.A. All rights reserved.