Performance of fiber hydrogen sensor based on π-shifted fiber Bragg grating coated with Pd/Ta composite films of different thicknesses

Rapid and accurate detection of hydrogen in anaerobic condition is more and more important for the safe production and operation of hydrogen energy. A novel fiber hydrogen sensor based on Pd/Ta composite film coating on π-shifted fiber Bragg grating is proposed and its sensing performance is evaluated experimentally. Due to the narrow reflective peak of π-shifted fiber Bragg grating, the proposed sensor has, shown higher accuracy on wavelength shift tracing. A Pd/Ta composite film was deposited on the side of π-shifted fiber Bragg grating by magnetron sputtering process. Compared with the grating hydrogen sensors of other Pd-based composite films, the hydrogen sensitivity and response time of the Pd/Ta composite film coated sensors with different thickness of sensing layer have been improved greatly. When the hydrogen concentration is 1%, The wavelength shifts of π-shifted fiber Bragg grating of Pd/Ta membrane with thicknesses of 100 nm, 200 nm, 300 nm and 800 nm are 16, 31, 50 and 115 pm, respectively, and the response time are 63, 71, 109 and 150 s, respectively. A longtime testing of the sensor proves that the sensor has good long-term stability and repeatability. The proposed hydrogen sensor with Pd/Ta composite film has great potential in the quasi-distributed monitoring of hydrogen leakage in hydrogen generation, refueling stations, and so on.