Fiber Bragg grating refractive index sensor based on double D-shaped fiber

FBG based refractive index sensors are widely used in sensing applications such as structural health monitoring, oil exploration, refractive index measurement of chemical solutions, etc., owing to benefits of FBG such as small size, real time monitoring, high resolution, resistant to high temperature and various chemicals, etc. In this paper, simple and high sensitive method employing a double D-shaped FBG (DDSF) for refractive index (RI) measurements of glucose solution is proposed and investigated. The operating principle is based on the exploitation of the evanescent wave interaction of the propagating light with the surrounding external environment, resulting in shift of Bragg wavelength. Wavelength shift is measured, when the refractive index of external medium changes from 1.33 to 1.43 approximately for glucose solution with varying concentrations, exhibiting a good linear relationship between them. By changing the depth of the D-shaped groove, the sensor's sensitivity can optimize. A high sensitivity of 47.37 nm/RIU is achieved, which indicates that proposed sensor has provided high sensitivity and linearity.

Automated summary

This paper proposes and investigates a simple and highly sensitive method using a double D-shaped fiber Bragg grating (DDSF) for refractive index measurements of glucose solution. The operating principle is based on the evanescent wave interaction of propagating light with the surrounding external environment, resulting in a shift of the Bragg wavelength. The wavelength shift is measured when the refractive index of the external medium changes, showing a good linear relationship.