Abstract:
A novel laser machined spiral microstructure fiber Bragg grating (FBG) hydrogen sensor coated
with composite sensing film is presented. The sensor probes are sputtered with Pd/Ni and
Pd/Ag film respectively. The atomic ratio of the Pd/Ni and Pd/Ag composite films is controlled
at 87:13 and 4:1 respectively. Experimental results demonstrate that a pitch 60 μm FBG with
double spiral microstructures, coated with 520 nm Pd/Ni and Pd/Ag film has hydrogen gas
sensitivity in air of 13 pm/%H and 25 pm/%H respectively. The laser ablated spiral
microstructured probes with composite films showed greater sensitivity compared with
standard FBG probes with similar coating. The optimum testing temperature (50 °C) enhanced
the sensitivity and repeatability of the probes. Due to its high gas response and reversibility, the
sensor probe is a potential candidate for hydrogen monitoring.
