Monochromatic excitation of surface plasmon resonance in an optical-fibre refractive-index sensor

A simple and inexpensive refractive-index sensor is described. The transducer is a multimode optical fibre which has been metallized with gold on the sensing area. The principle of this sensor is based on surface plasmon excitation at the metal/dielectric interface. This set-up, which uses monochromatic incident light, can work as an optical-fibre refractometer or as a refractive-index-variation optical-fibre sensor, in a range between 1.33 and 1.40. This sensor can detect a refractive-index variation around 10(-4) and can measure a refractive index with an accuracy around 2 x 10(-4).