Fiber Bragg gratings are used e. for fixing the wavelengths of fiber lasers, for filtering out certain wavelength components, for gain flattening of fiber amplifiers, and in fiber-optic sensors. A fiber Bragg grating (FBG) is a type of distributed Bragg reflector constructed in a short segment of optical fiber that reflects particular wavelengths of light and transmits all others. This is achieved by creating a periodic variation in the refractive index of the fiber core, which generates a. 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. 📦 For purchasing, use the RP Photonics Buyer's Guide for Bragg gratings. In this article, we will explore the definition, historical background, and importance of FBGs in modern optics.