Greatly etched fiber Bragg grating hydrogen sensor with Pd/Ni composite film as sensing material

Pd/Ni composite film was deposited on the side-face of chemically etched fiber Bragg grating as sensing element by magnetron sputtering process. The composition, structure and micro morphology of Pd/Ni composite film were investigated by energy dispersive X-ray analysis (EDAX), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The atomic ratio of Pd:Ni in Pd/Ni composite film is controlled at about 91:9. XRD result proves that the Pd/Ni composite film has good structural stability during hydrogen absorption and desorption process. During the hydrogen response experiment, central wavelength shift of the etched FBG increases linearly with the increase of hydrogen concentration. When the hydrogen concentration is 4% in volume ratio, wavelength shift of the etched FBG is about 60 pm, and the hydrogen sensor is not sensitive to methane. The experimental results show the sensor's hydrogen response is reversible, and the hydrogen sensor may have great potential for hydrogen's distributed measurement.