A simple and unique methodology predicting the influence of metal film coating, on non-adiabatic tapered fibers constituting single-fiber Mach-Zehnder interferometer (SF-MZI) configuration, on output fringe pattern of the interferometer, without inducing surface plasma resonance, has been proposed. The suggested approach reveals increase in losses and degree of fringe shift in the output wavelength spectrum of the SF-MZI depending on the properties and thickness of the metal deposited on fiber tapers. In order to substantiate the theoretical findings, layers of aluminium (Al) metal of different thicknesses are deposited on tapered regions of the SF-MZI and refractive index sensing experiments for identifying the presence and concentration of Fluoride ions and Sucrose in water are conducted. The impression of metal coating envisaged by the proposed methodology in terms of sensitivity enhancement (from 291.43 nm/RIU to 368.57 nm/RIU for Fluoride ion and 33.85 nm/RIU to 77.89 nm/RIU, for Sucrose solution), exponential decay of extinction ratio (with attenuation parameter of 0.05 nm-1 and 0.037 nm-1 for Fluoride ion and Sucrose sensing, respectively), fluctuations in free spectral range (FSR) (from 0.6 to 1.3 nm) at the output port of the interferometer have been quantified and validated by the experimental findings.
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