Hydrogen leak detection by means of fiber Bragg gratings covered by a catalytic sensitive layer

In this paper, we present a novel hydrogen sensor based on a fiber Bragg grating covered by a catalytic sensitive layer. In presence of hydrogen in air, an exothermic reaction occurs in the sensitive layer made of a ceramic doped with noble metal. This chemical reaction leads to an increase of temperature around the fiber Bragg grating, which consequently shifts the Bragg wavelength. The sensing mechanism is thus simply based on the monitoring of the Bragg wavelength shift. The sensor response is linear and without hysteresis between increasing and decreasing hydrogen concentrations. It is also selective and extremely fast. Different experiments obtained on uniform fiber Bragg gratings of different physical lengths are reported in this paper.