A fiber Bragg grating (FBG) is a type of optical fiber that is used in cables to provide a specific wavelength of light. It is a type of distributed feedback grating, which consists of a periodic variation of the refractive index of the core of the fiber. This changes the conditions for total internal reflection, causing Bragg scattering to occur at the wavelengths determined by the period and refractive index. As a result, the FBG reflects the desired wavelength of light, while allowing other wavelengths to pass through.
FBGs are commonly used in optical cables, such as those used in communications networks. They provide a reliable way to filter out specific wavelengths, allowing for precise control of the transmitted light. This can allow for improved signal quality and reduced power consumption. FBGs are also used in sensing applications, where they can detect changes in strain and temperature.
FBGs are made by introducing a periodic variation in the refractive index of the fiber core, either by etching or by using an ultraviolet light source. This change in the refractive index creates a periodic structure along the length of the fiber, which allows for Bragg scattering to occur at the desired wavelength. The grating is usually created in-situ during the manufacturing process, and the exact parameters of the grating can be changed to create different wavelengths of light.
FBGs are a versatile technology that can be used in many different types of cables, from data communications to sensing applications. They provide a reliable way to filter out a specific wavelength of light, while allowing others to pass through, making them a valuable tool in many applications.