Ultra-highly sensitive hydrogen sensor based on fiber Fabry-Perot interferometer with Pt/WO3 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 (SMF) 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 two interference dips was -20.3 nm upon exposure to similar to 20000 ppm hydrogen concentration. The hydrogen sensitivity of the sensor was estimated to be better than 1 pm/ppm.