Development of a Dual-Color Optical Fiber SPR Sensor

Abstract

This paper presents a dual-color optical fiber surface plasmon resonance (SPR) sensor for a portable and low cost sensing system with high resolution. Principle of the proposed SPR sensor is based on the differential reflectance method. Light from two light emitting diodes (LEDs), which are alternately flashed with a constant cycle, is fed to a sensing part via two optical couplers. The reflected light is detected by a photodiode. Changes of reflectance at two wavelengths are proportional to the refractive index change of a sensed medium. Taking the difference of reflectance at these two wavelengths makes the sensitivity almost twice. Measuring ethanol solutions with different refractive indices reveals that this sensor responds to the refractive index change linearly over the range of from 1.333 to 1.3616. From the noise analysis of the output signal of the sensor, the limit of detection (LOD) of the refractive index is estimated to be 5.2 times 10-4