Research on Refractive Index and Temperature Measurement Based on S-Shaped SPR Fiber Sensor

The paper proposes an S-shaped fiber Surface Plasmon Resonance (SPR) sensor structure capable of simultaneously measuring refractive index (RI) and temperature for the first time. The innovative sensor design integrates multi-mode fiber, single-mode fiber, and coreless fiber. A section of the S-shaped sensing region is created by heating a single-mode fiber with a heating rod, upon which a 50 nm Au film is deposited to induce the SPR phenomenon for RI measurement. Another section of the S-shaped sensing region is formed by heating a coreless fiber, also with a heating rod, and coating it with a 50 nm Au film and polydimethylsiloxane (PDMS) for temperature measurement. The complete S-shaped fiber sensor facilitates simultaneous RI and temperature measurements. It exhibits a high sensitivity of 2864.52 nm/RIU within the RI confines of 1.3339 to 1.3746 RIU and a high sensitivity of -1.6107 nm/degrees C within the temperature confines of 30 to 65 degrees C. This S-shaped fiber sensor demonstrates remarkable repeatability and stability, with the maximum measurement error being 0.00028 RIU for RI and 0.31 degrees C for temperature. Characterized by its simplicity, low cost, and compact size, this sensor is well-suited for broad applications in biochemical analysis and temperature monitoring within complex environments.