Special types are covered in depth, including apodized gratings for suppressing spectral sidelobes, chirped gratings for dispersion compensation and pulse stretching, tilted gratings to create notch filters, and long-period gratings for gain equalization. This article explains what fiber Bragg gratings (FBGs) are: periodic modulations of the refractive index in a fiber core which reflect a narrow wavelength band according to the Bragg condition $lambda =2{textstyle phantom{rule{0. 222em}{0ex}}}{n}_{text{eff}}{textstyle. In the vast realm of optical fiber sensing, where precision and innovation converge, Fiber Bragg Gratings (FBGs) stand as luminaries, casting their influence across myriad applications. There are many types of fiber Bragg gratings.