Importance of cladding in an optical fiber

An optical fiber consists of core and cladding. Core is a cylinder which is surrounded by a cylindrical shell called as cladding. Cladding refractive index is slightly lower than the core refractive index. Thus core is optically denser and cladding optically rarer. This difference in refractive indices facilitates multiple total internal reflections which is the basic principle for light transmission in an optical fiber. Cladding also adds mechanical strength to the fiber. Cladding is very effective in protecting fiber from absorbing surface contaminants. There is always a chance of presence of dielectric discontinuities at the core surface. This may result in huge scattering loss. The cladding helps to reduce this scattering loss. Nowadays glass material is sued for the construction of core and plastic material for the construction of cladding. Cladding refractive index remains constant in both step index and graded index fiber.