optical fiber

A filament of transparent dielectric material, usually glass or plastic, and usually circular in cross section, that guides light . (188 ) Note 1: An optical fiber usually has a cylindrical core surrounded by, and in intimate contact with, a cladding of similar geometry. Note 2: The refractive index of the core must be slightly higher than that of the cladding for the light to be guided by the fiber. Synonym lightguide.