Improved Etalon-Type Fiber-Optic Hydrogen Sensors

Three modifications have been proposed for hydrogen sensors in which hydrogen in the air causes changes in the reflection spectra of interferometric film stacks that are interrogated via optical fibers. One of the films in the stack in each such sensor contains palladium, which reacts with hydrogen to form palladium hydride. The differences between the optical absorbances and indices of refraction of palladium and palladium hydride give rise to observable changes in spectra.