Eccentric Core Optical Fiber SPR Sensor for Refractive Index Sensing Characteristics

This study proposes an eccentric core optical fiber biosensor based on the surface plasmon resonance phenomenon, utilizing COMSOL Multiphysics 6.2 finite element method (FEM). An Ag film with a thickness of 30nm is coated on the cladding of the eccentric core optical fiber. The analytical layers employed include air, water, blood plasma, and a self-set refractive index (RI) of 1.373. A 5-nm thick TiO₂ layer is coated between the Ag film and the analyte. This TiO₂ layer not only prevents the Ag layer from oxidation but also enhances the sensor’s sensitivity. The sensor serves as a theoretical foundation for experimental research. The wavelength sensitivities have been calculated, with the self-set RI of 1.373 exhibiting the maximum sensitivity of 1785.714 nm/RIU and a resolution of 5.60 × 10⁻⁵ RIU. The proposed sensor presents itself as a promising candidate for a low-cost, simple-geometry biochemical sensing solution.