Modal interferometric refractive index sensing in microstructured exposed core fibres

TL;DR

This paper introduces a novel interferometric refractive index sensor using microstructured exposed-core fibres, achieving high sensitivity for physiological sensing in challenging biological environments.

Contribution

It proposes a new fibre sensor design with mode splitting and interferometry for enhanced sensitivity in biological applications.

Findings

Achieved sensitivity of up to 60,000 rad/RIU-cm.

Demonstrated robustness for sensing in hard-to-reach biological tissues.

Mode splitting enables stable interferometric measurements.

Abstract

Optical fibre-based sensors measuring refractive index shift in bodily fluids and tissues are versatile and accurate probes of physiological processes. Here, we suggest a refractive index sensor based on a microstructured exposed-core fibre (ECF). By considering a high refractive index coating of the exposed core, our modelling demonstrates the splitting of the guided mode into a surface sensing mode and a mode that is isolated from the surface. With the isolated mode acting as a reference arm, this two-mode one-fibre solution provides for robust interferometric sensing with a sensitivity of up to 60,000 rad/RIU-cm, which is suitable for sensing subtle physiological processes within hard-to-reach places inside living organisms, such as the spinal cord, ovarian tract and blood vessels.