Dual-channel fiber-optic surface plasmon resonance sensor with cascaded coaxial dual-waveguide D-type structure and microsphere structure

To address the restriction of fiber-optic surface plasmon resonance (SPR) sensors in the field of multi-sample detection, a novel dual-channel fiber-optic SPR sensor based on the cascade of coaxial dual-waveguide D-type structure and microsphere structure is proposed in this paper. The fiber sidepolishing technique converts the coaxial dual-waveguide fiber into a D-type one, and the evanescent wave in the ring core leaks, generating a D-type sensing region; the fiber optic fused ball push technology converts the coaxial dual waveguides into microspheres, and the stimulated cladding mode evanescent wave leaks, producing the microsphere sensing region. By injecting light into the coaxial dual-waveguide middle core alone, the sensor can realize single-stage sensing in the microsphere sensing area; it can also realize dual-channel sensing in the D-type sensing area and microsphere sensing area by injecting light into the ring core. The refractive index measurement ranges for the two channels are 1.333-1.365 and 1.375-1.405, respectively, with detection sensitivities of 981.56 nm/RIU and 4138 nm/RIU. The sensor combines wavelength division multiplexing and space division multiplexing technologies, presenting a novel research concept for multi-channel fiber SPR sensors.