An All-Fiber Reflective Hydrogen Sensor Based on a Photonic Crystal Fiber In-Line Interferometer

A new method based on introducing a photonic crystal fiber (PCF) in-line interferometer for hydrogen sensing is demonstrated. One end-face of the PCF and part of the outer-face of the fiber are plated with a thin palladium film by magnetron sputtering, while the other end is connected to the optical path. Therefore, a set of reflection-type all-fiber hydrogen sensor system is accomplished. Hydrogen concentration from 0% to 5% was detected in the experiment and the related interferometric resonant wavelength-shift was recorded. The maximum wavelength shift is over 1.2 nm. The whole system has an all-fiber optical path without any bulk-optic components, and this design obtains a high level of integration, a high stability, and low production costs.