Optical fiber hydrogen sensor with single Sagnac interferometer loop based on vernier effect

An optical fiber hydrogen sensor with single Sagnac interferometer loop based on vernier effect has been proposed. The vernier effect is achieved by angle shift splicing two polarization maintaining fibers (PMFs) in single Sagnac interferometer loop. The hydrogen sensing length of PMF is 2 cm which is coated with Pt-loaded WO3/SiO2 powder. When the Pt/WO3 film is exposed to hydrogen, the redox reaction releases the temperature on the PMF, which induces the wavelength shift of the optical fiber sensor. The temperature sensitivity is −2.44 nm/°C and the hydrogen sensitivity is −14.61 nm/% within the range of 0%-0.8% (vol%), which is 1.85 times higher than the Sagnac sensor without vernier effect. The hydrogen sensitivity is related to the length of the PMF coated with Pt-loaded WO3/SiO2. The sensor is easy to fabricate, selective and high sensitivity.