M. Tabib-azar et al., Highly sensitive hydrogen sensors using palladium coated fiber optics withexposed cores and evanescent field interactions, SENS ACTU-B, 56(1-2), 1999, pp. 158-163
A novel fiber optic hydrogen sensor which is constructed by depositing pall
adium over an exposed core region of a multimode fiber is reported. The sen
sing mechanism is based on evanescent field interaction with the palladium
coating. Since the length, thickness, and composition of the palladium patc
h can be controlled independently of each other, it is possible to increase
the speed of our sensor at lower temperatures while maintaining its sensit
ivity. In micromirror sensors such an optimization is not possible due to a
restriction imposed on their active area of interaction by the fiber optic
cross-section. Micromirror fiber optic sensors, studied in the past, take
advantage of the reflection/absorption of a palladium film deposited at the
end of a fiber resulting in one sensor per fiber optic strand. On the othe
r hand, many evanescent field-based sensors can be deposited over a single
fiber optic strand. Using a 100 Angstrom thick palladium with 1.5 cm intera
ction length we could detect hydrogen in the 0.2-0.6% range with correspond
ing response times of 30-20 s at room temperature. At -10 degrees C, these
response times increased by a factor of only 2. (C) 1999 Elsevier Science S
.A. All rights reserved.