Modeling of a fiber-optic sensor based on surface plasmon resonance including the dispersion of the analyte

A model of surface plasmon resonance fiber-optic sensor based on the theory of attenuated total internal reflection is presented. Because of the mathematical complications related to rigorous theory of cylindrical optical waveguides, the analysis is carried out in frame of optics of multilayered media. The sensing scheme uses a wavelength interrogation method and the calculations are performed over a broad spectral range. The influence of the dispersion of the analyte on the sensor performance is considered and discussed. Model computations are performed for two mostly used types of excitation conditions. In the first case, the usage of a focused beam from the collimated light source is considered. The second case is related to the excitation of the fiber by a diffusive source. According to the excitation conditions, the contribution of meridional rays, or skew and meridional rays has to be taken into account. The calculation of optical power transmitted through the multimode sensing fiber is carried out. The effects of the layered structure thicknesses on surface plasmon resonance as well as the influence of the parameters describing the considered fiber are discussed. The influence of the analyte dispersion on the sensitivity, detection accuracy and signal to noise ratio is discussed.