# Refractive index sensing with temperature compensation by a multimode-interference fiber-based optical frequency comb sensing cavity

## TL;DR

This paper introduces a fiber-based optical frequency comb sensor that simultaneously measures refractive index and temperature, achieving high precision and enabling improved RI sensing applications.

## Contribution

A novel MMI fiber-based OFC sensing cavity that enables concurrent RI and temperature measurements with high accuracy.

## Key findings

- Achieved RI measurement precision of 1.6×10^-4 RIU.
- Achieved temperature measurement precision of 0.08°C.
- Demonstrated continuous, simultaneous RI and temperature sensing.

## Abstract

We proposed a refractive index (RI) sensing method with temperature compensation by using an optical frequency comb (OFC) sensing cavity employing a multimode-interference (MMI) fiber, namely, the MMI-OFC sensing cavity. The MMI-OFC sensing cavity enables simultaneous measurement of material-dependent RI and sample temperature by decoding from the comb spacing frequency shift and the wavelength shift of the OFC. We realized the simultaneous and continuous measurement of RI-related concentration of a liquid sample and its temperature with precisions of 1.6*10^-4 RIU and 0.08 degree. The proposed method would be a useful means for the various applications based on RI sensing.

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Source: https://tomesphere.com/paper/1905.04901