A novel type of fiber-optic cavity sensor for hydrogen diffusion into and out of fibers is presented. The sensor is an implementation of a cavity ringdown scheme in a silica-based single-mode fiber that has been exposed to gaseous hydrogen at normal pressure. The measured ringdown times during the H<sub>2</sub> diffusion show good agreement with a theoretical diffusion model. This model allows the determination of the diffusion coefficient of hydrogen in silica, resulting in <i>D</i> = (3.02 ± 0.07) × 10<sup>−15</sup> m<sup>2</sup>/s at 30 °C.
© 2003 Optical Society of America
(060.2370) Fiber optics and optical communications : Fiber optics sensors
(060.2430) Fiber optics and optical communications : Fibers, single-mode
(230.5750) Optical devices : Resonators
(300.1030) Spectroscopy : Absorption
Daniel E. Vogler, Michel G. Müller, and Markus W. Sigrist, "Fiber-Optic Cavity Sensing of Hydrogen Diffusion," Appl. Opt. 42, 5413-5417 (2003)