Characterization of hydrogen sensors based on palladium-electroplated fiber Bragg gratings (FBG)

The response of a new type of hydrogen sensors based on electroplated palladium on Fiber Bragg Gratings (FBG) is demonstrated. Sensor response is characterized from 35 degrees to 95 degrees Celsius at 0.6% hydrogen in nitrogen and from 0.1% to 4% hydrogen at 95 degrees Celsius with air purging between each hydrogen cycle. The Bragg wavelength shift at saturation and the response times were used to analyze the data. The results showed that heat treatments in flowing air at 95 degrees Celsius to 150 degrees Celsius greatly improved the sensor response. A comparison of the experimental response times to those predicted by diffusion equations implied that temperature had a profound effect on hydrogen surface reaction probability.