Optical Fiber Refractive Index Sensor

Abstract

Optical sensing is an emerging field that may replace electronic sensing, in the same way that electronic sensing has replaced traditional mechanical sensing. In this project we explore the methods of optical sensing, utilizing optical fiber technology to develop a refractive index sensor that can be of benefit in many applications. The proposed sensor has a single mode-multimode-single mode fiber structure, with a coreless multimode fiber section sandwiched in-between two single mode fiber leads. The surrounding medium of the coreless fiber section acts as a cladding whose refractive index is sensed by monitoring the optical power transmitted through the fiber structure. Two methods of analysis have been used to study the proposed sensor characteristics, the finite difference beam propagation method (FD-BPM) and the Eigen function solution method, and the results are compared to works published in the literature. Proof of concept of the sensor working principle has been established using FD-BPM simulations. Pilot experiments with an available SMS structure have also been conducted.