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

An optical fiber probe sensor based on a tapered-fiber Bragg grating (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 deep ultraviolet femtosecond laser technology. A second FBG was inscribed in the 125 μm-fiber section for temperature compensation. The sensing head was able to detect H
₂
concentration in the range 0%-1% (v/v) H
₂
at room temperature; a maximum sensitivity of 81.8 pm/% (v/v) H
₂
was attained with temperature compensation. The influence of the Pd coating over temperature sensitivity of standard and tapered-FBGs is also presented.