Optimal refractive index design for an optical fibre-based evanescent field sensor

Abstract

Optical fibre-based evanescent field sensors are proving to be viable and useful in the detection of chemicals, toxins, gases and other species. Such fibre sensors rely on weak interactions between the surrounding environment and the external "evanescent" field associated with bound modes of electromagnetic radiation propagating through an optical fibre. Of fundamental importance in the design of such sensors is the fraction of the total guided field power that propagates as the evanescent field. By increasing this relative evanescent field power, sensor gain can be improved. As the evanescent field is determined by the refractive index profile (RIP) of the sensor and the surrounding environ..