Terbium doped strontium cerate enabled long period fiber gratings for high temperature sensing of hydrogen

This paper reports on a novel optical fiber based sensor for hydrogen detection at high temperatures (>600 °C). The optical sensor consists of a perovskite-type ceramic, SrCe0.95Tb0.05O3−δ, as the sensing material, which is coated on the cladding layer of long period fiber gratings. Upon exposure to hydrogen, the reduction of Ce4+ to Ce3+ on the surface of SrCe0.95Tb0.05O3−δ particle causes decrease in its refractive index. As a result, the resonance wavelength of long period fiber gratings shifts to a higher value. The rate of the shift is dependent on the hydrogen partial pressure and can be used as the sensing signal. The high temperature optical H2 sensor exhibits high sensitivity for H2 detection at a partial pressure of 0.005 atm, and a short response time. The sensor is reversible as exposing the sensor to air oxidizes Ce3+ to Ce4+.