Palladium-Based Hydrogen Sensors Using Fiber Bragg Gratings

Abstract

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.