Design and Simulation of C-Shaped Optical Fiber Sensor

This paper presents a C-shaped optical fiber sensor for refractive index measurement. The design and simulation of the C-shaped optical fiber were conducted via Wave Optics Module-COMSOL Multiphysics®. The refractive index measurement ranging from 1.30-1.40 is performed. The simulation results showed that the C-shaped design has the potential to act as a refractive index sensor with sensitivity of up to 0.966348101, higher than simulated D-shaped OFS with estimated sensitivity of up to 0.966334412.

I. Introduction

Optical fiber sensor (OFS), a well-known refractometer has been widely demonstrated in measuring physical, chemical, and biological parameters, offering simple refractive index (RI) measurement for quality control and in situ monitoring. To fabricate this optical miniature sensor, a part of the optical fibre cladding is modified and replaced with target measurand either in form of liquid, gas, or vapour to measure its various properties based on the RI changes. Microfiber OFS has strong sensitivity performance in which the cladding layer is fully modified to expose the evanescent field to interact with the sensing medium. However, after cladding modification, a small segment of the fiber becomes extremely thin, causing it to be fragile and hard to handle [1], [2]. To mitigate these drawbacks, side-polished OFS has been introduced where the one side of the fibre is polished to form a D-shaped structure. Despite the heightened mechanical stability from the cladding support as compared to the microfiber OFS, it has low sensitivity due to limited evanescent field exposure [3].