Palladium-Based Hydrogen Sensors Using Fiber Bragg Gratings

This paper reports on the development and evaluation of fiber optic hydrogen sensors based on fiber Bragg gratings. The sensors were tested in a newly developed measurement system for long term experiments of fiber optic gas sensors. Two types of palladium metal sensors were manufactured; sputter coated and a new concept using palladium foil. The sputter coated sensor has a 1600 nm palladium coating with a 30 nm titanium layer between the etched fiber and the palladium serving as an adhesion layer. The foil sensors have either a 20 μm or 100 μ m palladium foil attached to the fiber. The sensors were tested for different hydrogen concentration in a newly developed gas sensing test setup. The maximum wavelength change (at 90 °C and 1060 mbar with both 1% and 5% hydrogen in nitrogen) of the coated sensor, the 20 μm and the 100 μ m foil sensor was found to be 10, 160, and 80 pm respectively to 1% hydrogen and 25, 480, and 225 pm respectively to 5% hydrogen. A method is presented for calculating the wavelength change of the coated and foil sensors to show the current limitations and the theoretical future potential of each sensor.