Dual-Channel Optical Fiber Surface Plasmon Resonance Sensor for Trace-Level Cu2+ Detection and Temperature Compensation

To mitigate temperature-induced measurement inaccuracies in optical fiber sensors, a dual-channel surface plasmon resonance (SPR) sensor is proposed for trace-level Cu²⁺ detection with integrated temperature compensation capabilities. The SPR signal is generated through excitation by a silver film, and highly sensitive Cu²⁺ detection is achieved by modifying the fiber with chitosan (CS)/polyacrylic acid (PAA). Furthermore, by exploiting the modulation effect of a CeF₃ thin film on the SPR dip, the temperature SPR signal and the Cu²⁺ detection SPR signal are separated. After coating with polydimethylsiloxane (PDMS), temperature sensing is achieved and the temperature effect on the Cu²⁺ detection channel is quantified. Subsequently, compensation is applied using the corresponding sensitivity matrix. Experimental results demonstrate maximum sensitivities of 0.346 nm/(μmol/L) for Cu²⁺ detection and 3.856 nm/°C for temperature measurement. Compared with other temperature-compensated sensors, this sensor exhibits a simpler structure, superior performance, and obviates the need for complex signal processing. Thus, this work provides a novel strategy for developing multi-parameter temperature-compensated optical fiber sensors.