Interferometric fibre-optic hydrogen sensor

A hydrogen sensor has been developed in which the sensing element is a palladium wire, mechanically attached to a monomode optical fibre. In the presence of hydrogen, the palladium is converted to palladium hydride, with consequent changes in the physical dimensions of the wire. In turn, these dimensional changes produce a longitudinal strain in the optical fibre. The strain is transduced to a phase retardance in a light beam guided by the fibre, and which is recovered interferometrically. The sensor has been demonstrated in a nitrogen atmosphere at laboratory temperature. The phase retardance is proportional to the square root of the hydrogen partial pressure, and has been demonstrated in the partial pressure range 0-100 Pa, with an accuracy of +or-2 Pa.