Conclusion: Measuring grating density is a crucial step in optimizing their design and fabrication. Fiber grating has many advantages such as compact size, good wavelength selectivity, nonlinear effects immunity, polarization insensitivity, fiber system inherent compatibility, ease to use and maintenance, wide bandwidth range, and low additional loss, combined with highly developed fiber grating. Fiber Bragg grating (FBG) sensors have emerged as advanced tools for monitoring a wide range of physical parameters in various fields, including structural health, aerospace, biochemical, and environmental applications. This review provides a comprehensive overview of FBG sensor technology. The bandwidth, reflection profile, and phase response of gratings require special measurement techniques for proper characterization. Researchers have gained enormous attention in the field of fiber Bragg grating (FBG)-based sensing due to its. A variation of the period of the grating inscripted in a fiber optic – induced by mechanical or thermal perturbation – causes a shift of the reflected peak wavelength, due to the related optical path length variation. The principle involves creating an interference pattern between a reference beam and a beam diffracted by the grating.