An optical fibre surface plasmon resonance (SPR) sensor has been
developed for the detection of hydrogen leakages. A thin
palladium layer deposited on the bare core of a multimode fibre
was used as the transducer. In this device, modification of
the SPR is due to variation in the complex permittivity of
palladium in contact with gaseous hydrogen. This effect is
enhanced by using selective injection of high-order modes in
the fibre via a collimated beam with non-normal incidence on the input
end of the fibre. Measurements of concentrations
as low as 0.8% of hydrogen in pure nitrogen have been found to be
possible. The response time varies between 3 s for pure hydrogen
and 300 s for the lowest concentrations. Such a large range can
be explained by the two different crystallographic phases of
the palladium-hydrogen system. Moreover, the response of the
sensor is dependent on the length of the sensing area. In
preliminary experiments, it has been possible to split the
sensing area in order to achieve a two-point detection
device.
Liquid hydrogen has been intensively used in aerospace applications for the past 40 years and is of great interest for future automotive applications. Following major explosive risks due to the use of hydrogen in air, several studies were carried out in order to develop optical fibre sensors for the detection of hydrogen leakage. This paper aims at the presentation of new hydrogen sensors based on the use of fibre Bragg gratings (FBG) and long period gratings (LPG) coated by palladium nanolayers. The sensing principle based on the palladium-hydrogen interaction is presented, as well as experimental results. It is shown that both techniques could be used for hydrogen sensing but with a sensitivity enhanced by a factor up to 500 when using a LPG sensor. FBG sensors appear to be pure strain sensors and LPG sensors are mainly based on the coupling between the cladding modes and evanescent or surface plasmon waves. Preliminary results obtained with an in-fibre Mach-Zehnder interferometer configuration with in-series LPG sensors are also presented. They show potential interest to compensate for the thermal sensitivity of the fibre gratings.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.