An extrinsic Fabry-Perot interferometric optical fiber sensor system for hydrogen detection

An extrinsic Fabry-Perot interferometric (EFPI) optical fiber hydrogen sensor based on palladium silver (Pd-Ag) film is designed for hydrogen leakage detection. The sensing mechanism of such a sensor is based on the mechanical stress that is induced in the Pd-Ag film when it absorbs hydrogen. The sensor system which is portable and suitable for field detection is formed by a conventional coupler, a low-power LED operating at 850 nm, and a high resolution miniature spectrometer. To obtain the absolute length of the EFPI air gap, a cross-correlation signal processing method is introduced.The sensor is suitable for monitoring concentrations of hydrogen below the lower explosive limit.