Implementation of Long-Period Fiber Gratings for Refractive Index Measurement of Liquids

Abstract

Refractive index (RI) is one of the optical parameters that is of paramount interest in characterizing liquid solutions and solvents. Increased public awareness and legal requirements for quality standards in different sectors have created a need for reliable, fast, automated, remote and/or portable refractive index sensors with multi-measurement capability. The fiber-based RI sensors are very good candidates in providing attractive solutions in such application areas and have been attracting a growing interest by the scientific community. In this work, a fiber optic refractive index sensor has been investigated. It uses a long-period fiber grating (LPFG) and an Optical Spectrum Analyzer (OSA), as sensor head and interrogator unit, respectively. New measurements of refractive indices of common solvents and solutions at the low-loss telecom wavelength band have been successfully demonstrated by using the proposed sensor. The reported measurement results are in excellent agreement with our simulation results and reference measurements realized by conventional measurement techniques.