<p>This study investigates the performance of two structures: basic SPR and solid core fiber configuration, by analytical and numerical approaches. The primary objective is to develop an analytical model considering important design parameters capable of accurately predicting resonance behaviour and to validate the findings through numerical simulation. The analytical model was formulated by considering guided mode interactions with surface plasmon waves under normal incidence conditions. Critical performance parameter, e.g. resonance wavelength, was derived as a function of the analyte’s refractive index. This modelling enabled the identification of design parameters most responsible for optimizing sensing performance before engaging in more resource-intensive numerical simulations. The analyte refractive index was varied between 1.33 and 1.40 to represent typical biological and chemical sensing environments. The comparison between analytical and simulation results for the resonance wavelength as a function of analyte refractive index demonstrated excellent agreement, with a coefficient of determination (R²) of approximately 0.99. However, the analytical model underestimated the sensitivity of the configuration with the cladding layer by approximately 8.6%, primarily because it does not account for the mode confinement and field distribution changes introduced by the cladding, which are captured in the full-wave simulation. While the simulation results indicate higher sensitivity in the cladded sensor configuration, the key focus lies in how closely the analytical model aligns with the numerical results. These results emphasize the importance of structural layering and provide a validated analytical foundation for efficient performance optimization in the waveguide sensors made by solid core optical fiber configuration.</p>