Abstract
Fiber Bragg Gratings (FBGs) are one of the most popular technology within fiber-optic sensors, and they allow the measurement of mechanical, thermal, and physical parameters. In recent years, a strong emphasis has been placed on the fabrication and application of chirped FBGs (CFBGs), which are characterized by a non-uniform modulation of the refractive index within the core of an optical fiber. A CFBG behaves as a cascade of FBGs, each one reflecting a narrow spectrum that depends on temperature and/or strain. The key characteristic of CFBGs is that their reflection spectrum depends on the strain/temperature observed in each section of the grating; thus, they enable a short-length distributed sensing, whereas it is possible to detect spatially resolved variations of temperature or strain with resolution on the order of a millimeter over the grating length. Based on this premise, CFBGs have found important applications in healthcare, mechanical engineering, and shock waves analysis, among others. This work reviews the present and emerging trends in CFBG sensors, focusing on all aspects of the sensing element and outlining the application case scenarios for which CFBG sensors have been demonstrated.
Highlights
Within the broad field of fiber optic sensors [1], Fiber Bragg Grating (FBG) sensors are emerging as a prominent technology [2,3,4,5,6,7]
Uniform FBGs are based on a periodical modulation of the refractive index in the core of an optical fiber [6,7], and they are the most popular grating-based type of technology
The results investigated in [82,83] show the capability of the chirped FBGs (CFBGs) to act as a distributed reflector on a length of 17 mm [82] to 115 mm [83]
Summary
Within the broad field of fiber optic sensors [1], Fiber Bragg Grating (FBG) sensors are emerging as a prominent technology [2,3,4,5,6,7]. FBG sensors find current application in healthcare and medical devices [10,11], structural engineering [5,12], oil and gas [13,14], harsh environments [9], monitoring in nuclear plants [15], high temperature sensors [16]. Recent advances such as draw-tower fabrication [17] enable the inscription of FBG arrays. The key characteristic of the FBG is that the Bragg wavelength changes linearly with strain and/or temperature, Sensors 2018, 18, 2147; doi:10.3390/s18072147 www.mdpi.com/journal/sensors
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
