Dual-Channel SPR Sensor Based on an Elliptical-Core Double-Hollow Fiber With Subwavelength Gratings

A dual-channel surface plasmon resonance (SPR) sensor is proposed, based on an elliptical-core double-hollow fiber that integrates subwavelength gratings (SWGs). By etching a microstructure with subwavelength periodicity on the outer wall of the fiber and depositing a metal layer, the coupling efficiency between the guided light and the metal interface can be significantly enhanced. We first demonstrate a subwavelength SPR sensor employing single-mode fiber and photonic crystal fiber, each showing several-fold improvement in performance. Furthermore, by extending this design to a dual-channel SPR sensor, simulations indicate that the refractive index (RI) sensitivity can exceed 15 000 nm/RIU in dual-channel detection, while also enabling temperature measurement with a temperature sensitivity of approximately −5 nm/°C. Compared with traditional single-channel fiber SPR sensors, the proposed structure not only offers higher sensitivity but also supports multi-parameter detection. Owing to its unique design, the design effectively reduces coupling between the two channels, thereby maintaining low channel crosstalk even under high-sensitivity conditions. This study introduces an innovative design for high-sensitivity, multi-parameter SPR fiber sensors. Broadening the application of SWGs in fiber sensing.