A robust fiber Bragg grating (FBG) hydrogen gas sensor for reliable multipoint-leakage monitoring has been developed. The\nsensing mechanism is based on shifts of center wavelength of the reflection spectra due to temperature change caused by\ncatalytic combustion heat. The sensitive film which consists of platinum-supported silica (Pt/SiO2) catalyst film was obtained\nusing sol-gel method. The precursor solution was composed of hexachloroplatinic acid and commercially available silica\nprecursor solution. The atom ratio of Si : Pt was fixed at 13 : 1. A small amount of this solution was dropped on the substrate\nand dried at room temperature. After that, the film was calcined at 500�°C in air. These procedures were repeated and therefore\nthick hydrogen-sensitive films were obtained. The catalytic film obtained by 20-time coating on quartz glass substrate showed a\ntemperature change 75 K upon exposure to 3 vol.% H2. For realizing robust sensor device, this catalytic film was deposited and\nFBG portion was directly fixed on titanium substrate. The sensor device showed good performances enough to detect hydrogen\ngas in the concentration range below lower explosion limit at room temperature. The enhancement of the sensitivity was\nattributed to not only catalytic combustion heat but also related thermal strain.
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