This paper presents a new hydrogen sensor based on a single mode-no core-single mode (SNS) fiber interferometer structure. The surface of the no core fiber (NCF) was coated by Pd/WO₃ film to detect the variation of hydrogen concentration. If the hydrogen concentration changes, the refractive index of the Pd/WO₃ film as well as the boundary condition for light propagating in the NCF will all be changed, which will then cause a shift into the resonant wavelength of interferometer. Therefore, the hydrogen concentration can be deduced by measuring the shift of the resonant wavelength. Experimental results demonstrated that this proposed sensor had a high detection sensitivity of 1.26857 nm/%, with good linearity and high accuracy (maximum 0.0055% hydrogen volume error). Besides, it also possessed the advantages of simple structure, low cost, good stability, and repeatability.
Keywords: Pd/WO3 film; fiber interferometer; hydrogen sensor; no core fiber (NCF).