Fundamental characteristics of a dual-colour fibre optic SPR sensor

• Published in: Measurement science & technology Vol. 17; no. 6; pp. 1547 - 1552
• Main Authors: Suzuki, Hitoshi, Sugimoto, Mitsunori, Matsui, Yoshikazu, Kondoh, Jun
• Format: Journal Article
• Language: English
• Published: IOP Publishing 01.06.2006
• ISSN: 0957-0233; 1361-6501
• DOI: 10.1088/0957-0233/17/6/036

In this paper, we present the fundamental characteristics of a novel dual-colour optical fibre surface plasmon resonance (SPR) sensor for a portable low-cost sensing system. The principle of the proposed SPR sensor is based on the differential reflectance method. Light from two light-emitting diodes (LEDs), which are flashing alternately with different wavelengths, is fed to a sensor 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 the medium of interest. Taking the difference in reflectance at two wavelengths improves the sensitivity almost twofold. Measuring ethanol solutions with different refractive indices reveals that the sensor has a linear response to the refractive index change from 1.333 to 1.3616. By measuring the stability in the time response we estimate that the limit of detection (LOD) of the refractive index is 5.2 X 10-4.