Fiber Bragg grating sensors with Pt-loaded WO₃ coatings for hydrogen concentration detection down to 200 ppm

A novel fiber optic hydrogen sensor was proposed and experimentally demonstrated. The sensing element was a fiber Bragg grating (FBG) covered with Pt-loaded WO₃ coating annealed at 315 °C for 1 h. At room temperature of 25 °C, the FBG hydrogen sensor has 448 pm wavelength shift toward 8000 ppm hydrogen, and it can detect hydrogen as low as 200 ppm. Experimental results show that ambient humidity has little effect on the performance of the FBG hydrogen sensor, whereas the sensitivity of the FBG hydrogen sensor will be decreased at lower ambient temperatures. The relationship between the wavelength shift of the proposed sensor and hydrogen concentration is proposed and discussed in this article. (paper)