A triple-channel optical fiber SPR sensor with high performance and low cost working below 1000 nm wavelength

In this paper, we propose for the first time a triple-channel optical fiber surface plasmon resonance (SPR) refractive index (RI) sensor with an operating band below 1000 nm. The sensor consists of a U-shaped multimode fiber, a multimode-single mode-multimode (MSM) fiber and a core-offset fiber. To improve the performance of the triple-channel sensor and reduce crosstalk, we optimized each channel. For channel 3, the U-shaped fiber sputtering method was improved to solve the problems of over-wide resonance spectrum, disturbance dip at 500 nm and spectral saturation. For channel 1 and channel 2, the resonance wavelength was separated by sputtering gold film with different thickness. In addition, the length of sensing region was optimized and the core-offset structure was introduced to reduce channel crosstalk and improve sensor performance. Finally, the performance of the triple-channel sensor was tested. In the range of 1.3320 to 1.3615 RIU, the RI sensitivity of the three channels reached 965.3 nm/RIU, 2160.8 nm/RIU and 5556.9 nm/RIU respectively. Compared with other multi-channel optical fiber SPR sensors, the sensor has excellent spectral characteristics, and all three channels work in the band less than 1000 nm, so it has the advantages of high precision and low cost, and has broad application prospects in high-throughput biochemical detection platform.