Theoretical investigation of a multi-channel optical fiber surface plasmon resonance hydrogen sensor

We investigate the use and operation of an optical fiber surface plasmon resonance multi-channel hydrogen sensor. The sensor consists of two or more Ag/SiO ₂/Pd multilayer structures coated at different locations along the cladding stripped core of an optical fiber. We demonstrate how the sensing response in one channel affects that in others by investigating the effects of the thicknesses of each layer on the sensor sensitivity, detection accuracy and figure of merit. We describe the individual roles of each layer in terms of the sensing and find that the parameter causing the largest degree of crosstalk between the channels is the thickness of the Ag layer which must be very carefully chosen as a result. We find that changes in the SiO ₂ and Pd layer thicknesses largely impact the channel in which the change is made so that there is a lot of freedom in choosing these. Finally, we demonstrate measurable operation from three, four, and six-channel sensors and illustrate the fundamental limitations which determine the number of channels which can be used in sensors based on this type of multilayer.