A distributed optical fiber sensor for hydrogen detection based on Pd, and Mg alloys

An optical fiber containing structured hydrogen sensing points, consisting of Palladium and/or Magnesium alloys is proposed and characterized. The sensitive layer is deposited on the outside of a multimode fiber, after removing the optical cladding. The sensor is based on a measurement technique which uses the Surface Plasmon Resonance effect. Compared to previous work1 which was performed at a single wavelength of 670nm, this study was done in the range of 450 to 900nm. A continuous change in intensity is observed as a function of the hydrogen concentration between 0.5% and 4% H2 in Ar. The response shows that the intensity transmitted can either decrease or increase, depending on the selected wavelength. The response time and the reproducibility of the detectors are also discussed. From our experiments and optical simulations we conclude that Pd covered indicator layers based on Mg alloys, such as Mg-Ti, would be even more advantageous compare to Pd layers thanks to their lower hydrogen equilibrium pressures. We will demonstrate an
extended sensitivity range by juxtaposing different materials over a fiber section, having different hydrogen equilibrium pressures.