H2 Sensing Based on a Pd-Coated Tapered-FBG Fabricated by DUV Femtosecond Laser Technique

An optical fiber sensor based on a tapered-FBG coated with 150 nm-thick Pd film is proposed for hydrogen detection. The FBG was written in a 50 µm-diameter tapered fiber by DUV femtosecond laser technology. A second FBG was inscribed in the untapered fiber section for temperature compensation. The sensing head was able to detect the variation of hydrogen pressure in the range 0-780 kPa and a maximum sensitivity of 0.15 pm/kPa was achieved. The sensing head was also submitted to increasing H2 concentration in the range 0-1 % (v/v) H2 and a maximum sensitivity of 81.8 pm/%(v/v) H2 was attained.