Leaky mode expansion for optical fibre sensor application

Abstract

A multimode interference (MMI) based sensor for high refractive index sensing was proposed and demonstrated in this simulation work. The proposed sensor scheme works by a mode expansion according to leaky modes instead of traditionally used radiation modes. The simulation work tried to exhibit whether and how light delivered multimode interference before it worn out. The MMI structure that was used in the simulation consists of a Single-mode-Multimode-Single-mode (SMS) fibres configuration. In this structure, the multimode fibre (MMF) segment was assumed to have only the core while the cladding was discarded and has a specific length. This work exhibited high refractive index (RI) sensing based on the Guided-mode-Leaky-mode-Guided-mode (GLG) structure or the SMS fibre structure previously cited by comprehending the fundamental theories of leaky mode expansion. The work also attempted to analyse the effects of important parameters of leaky mode expansion on sensing performances such as length and diameter of MMF, and changing value of surrounding refractive index. The simulation work was performed utilising BeamProp software to ascertain the needed power intensity and RI sensitivity to excite light into the MMF for detection. The economical and simple sensor structure is ideal in numerous applications, including for detection, diagnosis, health determination, safety, environmental, liquid food, and water quality control.