Dual channel optical fiber refractive index sensor based on surface plasmon resonance

Abstract

In this paper, an optical fiber refractive index sensor based on surface plasmon resonance (SPR) is presented. This sensor is able to measure the refractive index of two analytes simultaneously. The sensor structure is based on removing the cladding of an optical fiber and replacing it with thin films of silver and gold in the first and second channels respectively. The incident light inside the fiber excites surface plasmons which results in absorption at SPR wavelengths. For analyzing the proposed structure, finite difference time domain (FDTD) method is used. The absorption behavior depends on the dielectric constants of metal and sensing medium. Simulation results show that the proposed sensor has sensitivities about 1200 nm/RIU and 1650 nm/RIU and average figures of merits equal to 46 and 55 for the first and second channels respectively. The obtained transmission spectra prove that channels of the presented sensor work independently. According to the simulation results, this structure is suitable for multi-sensing applications.