Dual Parameter SPR Optical Fiber Sensor Based on TiO2 Coating Modulation for Detecting pH-Temperature With Low Crosstalk

This paper designed a based on surface plasmon resonance (SPR) optical fiber type low crosstalk pH value and temperature sensor. The sensor has the ability to detect pH value and temperature simultaneously, and can overcome the error factor caused by temperature changes in the pH value detection process of optical fiber sensors. Sensor is based on a multimode fiber (MMF) fused with a coreless fiber (NCF) to build the sensing substrate. Ag was used as SPR excitation material and polyacrylic acid (PAA)/ chitosan (CS) composite membrane was used for pH detection. Compared with previous research on temperature compensation, the SPR cascade sensing method treated by TiO₂/PDMS composite membrane significantly improved the temperature sensitivity of SPR signals and reduced crosstalk. This ensures that the SPR signal has a sufficient working range. In the range of −10 °C∼100 °C, the maximum temperature sensitivity can reach −4.1301 nm/°C, and the detection limit (DL) is 0.1542 °C. In the pH range of 4.08 ∼ 9.85, the sensor's pH sensitivity can reach up to −17.9359 nm/pH, and the resolution is 0.1272pH. Excellent sensing performance. The sensor is important for advancing future applications of high-precision temperature compensation detection, high-sensitivity pH biodetection, and SPR modulation technology.