Optical Fiber Hydrogen Sensor Based on the EVA/Pd Coated Hollow Fiber

A novel optical fiber hydrogen sensor based on the dielectric/metal coated hollow fiber structure is proposed. The palladium (Pd) and ethylene-vinyl acetate (EVA) layers are sequentially coated on the inner surface of the hollow core of the silica capillary to fabricate the EVA/Pd coated hollow fiber sensor. Theoretical ray transmission model is carried out to analyze the influence of the thicknesses of the Pd and EVA films. The experimental transmission spectra of the proposed sensor filled with hydrogen gas of different concentrations are measured. The experimental results show that the interference peak in the spectrum has a red shift with the increase of hydrogen concentration. Then the hydrogen concentration can be obtained by measuring the wavelength of the interference peak. In the range of 0–4% hydrogen concentration, the total shift is 10.64nm and the average sensitivity is 2.66 nm/%. Compared to other optical fiber hydrogen sensors, the proposed sensor has the advantages of simple structure, easy fabrication, low cost, high sensitivity and good safety performance.