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.