Fiber Optic Hydrogen Sensor Based on Fabry–Perot Interferometer Coated With Sol-Gel Pt/WO 3 Coating

A miniaturized fiber tip Fabry-Perot interferometer (FPI) with Pt/WO3 coating was demonstrated as a hydrogen sensor. The air-cavity of FPI was formed by inserting a single mode fiber into a partially polymer-filled glass capillary, which was highly sensitive to temperature. A layer of Pt/WO3 was coated on the glass capillary of the FPI serving as a reaction heater upon hydrogen exposure. The heat locally raised the FPI temperature, which led to the wavelength shift of interference spectrum. The average wavelength shift of sensor's two interference dips was -20.3 nm upon exposure to ~20000-ppm hydrogen concentration. The hydrogen sensitivity of the sensor was estimated to be better than 1 pm/ppm.