A Highly Sensitive Electro Optic-SPR Optical Fiber Sensor for Micro-Voltage Monitoring

This paper presents a novel optical fiber voltage sensing technology based on the electro-optic effect and surface plasmon resonance (SPR) effect. By monitoring the refractive index changes of the electro-optic material (DMF) under an electric field and leveraging the high-sensitivity response of SPR, high-precision optical detection of minute voltages is achieved. Experimental results demonstrate that the sensor achieves sensitivities of-1.3518 nm/mV and-0.8018 nm/mV in the ranges of-80 mV to-70 mV and 30 mV to 40 mV, respectively. Based on this sensing mechanism, a grooved photonic crystal fiber structure with integrated trench confinement and optimized air-hole layout is further proposed, which strengthens the interaction between the optical field and DMF and enhances the surface plasmon excitation via a TiO2 overlayer. Through this structural optimization, the sensitivity is improved to −1.65nm/mV, accompanied by excellent linear response characteristics. This study validates the feasibility and advantages of the electro optic–SPR coupling mechanism for micro-voltage detection. The proposed technology offers benefits such as non-invasiveness, immunity to electromagnetic interference, high integration, and good stability, providing a new approach for monitoring neural electrophysiological activity.