Ultra-Wide-Range SPR Fiber-Optic Sensing System for Multiparameter Detection in Complex Aqueous Environments

To address the strong coupling, large-gradient variations, and temperature cross-sensitivity among multiple physicochemical parameters such as refractive index (RI), pH, and temperature in complex aqueous environments, an ultra-wide-range surface plasmon resonance (SPR) fiber-optic sensing platform is proposed. By constructing three independent sensing regions (Ag, Ag/TiO₂, and Ag/MoS₂), multi-channel spectral gradient partitioning and direct signal mapping are realized, thereby avoiding signal overlap and reducing demodulation complexity. Specifically, the natural hydroxyl binding sites on the TiO₂ surface are utilized to load the PAA/CS polyelectrolyte sensitive membrane to construct a pH-responsive interface; MoS₂ combined with PDMS is used to achieve temperature sensitivity; and the Ag interface is used for RI detection. In addition, the matrix demodulation method is adopted to compensate for temperature-induced cross-sensitivity in the RI and pH channels. The experimental results demonstrate that this sensor can simultaneously detect RI (1.333-1.403), pH (3.22-13.21), and temperature (-20-100 °C), and maintain high accuracy and sensitivity within a wide dynamic range. This research can effectively address the issue of the coordinated changes in RI, pH, and temperature, providing an effective optical fiber sensing solution for the high-precision monitoring of multi-parameter coordinated changes in complex aqueous environments.