Abstract
Hydrogen is one of the next generation energies in the future, which shows promising applications in aerospace and chemical industries. Hydrogen leakage monitoring is very dangerous and important because of its low ignition energy, high combustion efficiency, and smallest molecule. This paper reviews the state-of-art development of the fiber optic hydrogen sensing technology. The main developing trends of fiber optic hydrogen sensors are based on two kinds of hydrogen sensitive materials, i.e. palladium-alloy thin films and Pt-doped WO3 coatings. In this review work, the advantages and disadvantages of these two kinds of sensing technologies will be evaluated.
Highlights
Hydrogen is a promising candidate for the generation energy due to its excellent characteristics such as cleanness, high efficiency, and renewability
Compared to fiber Bragg grating (FBG)-125 μm, FBG-20.6 μm can increase the sensitivity by 400%, and the FBG hydrogen sensitivity can be significantly improved by etching the FBG to a proper content
Palladium has been intensively investigated due to its obvious optical constant alternation when exposed to hydrogen, this metal film is susceptible to mechanical damage such as cracking, blistering, and delamination caused by the phase transition in the process of repeated absorption and desorption of hydrogen
Summary
Hydrogen is a promising candidate for the generation energy due to its excellent characteristics such as cleanness, high efficiency, and renewability. The wavelength shift of composite films has little optical power loss, the FBG hydrogen sensor toward 4% hydrogen is which can ensure its distributed measurement about 143% more than that of FBG-17 μm coated capability. The wavelength shift of the etched FBG coated hydrogen sensor under different hydrogen with the Pd film is expressed by (2) in [40], where concentrations. The FBG hydrogen sensor still has the 4-pm wavelength shift towards 400 ppm hydrogen, which proves it can detect the low concentration hydrogen at 0 °C
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