Fabricate a highly sensitive surface plasmon resonance optical fiber sensor based on a D-shape fiber coated with gold (Au) nano-layer

•This study focused on developing a high-sensitivity D-shape fiber sensor based on a surface plasmon resonance.•The suggested sensor for measuring the refractive index (RI) of material is influenced by two variables: polishing depths (D) and detecting lengths (L). In this study, a D-shape fiber coated with a gold (Au) nano-layer is proposed as the basis for a highly sensitive surface plasmon resonance (SPR) optical fiber sensor that is used to detect the refractive index RI of the glucose solution, with the possibility of using this sensor as a biosensor. By variety side-polishing multimode fiber with different sensing lengths (1 cm, 1.5 cm, and 2 cm) and coating it with a thin layer of 50 nm gold film, the SPR D-shape fiber sensor was developed. The impacts of the sensing area and various residual fiber thicknesses are explored in order to acquire the optimal values of the SPR D-shape fiber sensor. Observations revealed that various concentrations of glucose, ranging from 1% to 9%, were tested on an SPR D-shape fiber sensor, with sensitivity growing to 3.101 au. RIU−1 and linearity reaching 98%. The sensor responded quickly to the refractive index from 1.334 to 1.346 RIU. The future of glucose sensors looks bright with gold-coated D-shaped fiber sensors, they may also work well with other factors like temperature or strain due to their excellent sensitivity, stability, and repeatability.