د.السائح محمد الهباشي2026-11-012026-11-01https://dspace.academy.edu.ly/handle/123456789/2705Communication using an optical carrier wave guided along a glass fiber has a number of extractive features , several of which were apparent when the technique was originally started .Optical fiber have very small diameters which are often no greater than the diameter of human hair ( from eight micrometers for step index up to 25 micrometers for graded index ) .The fiber consist of a solid cylinder of transparent material , the core surround by a cladding of similar material . but having slightly lower refraction index , the refractive index of the core must be larger than that of the cladding this variation could be in step index or graded index . light waves propagate down the core in a series of plan wave fronts or modes.The telecommunication system are a key infrastructure of all modern societies and the optical fiber communications is the backbone of the telecommunication system . An optical communication system is comprised of many optical electrical and electronic devices and components .Optical fibers are replacing copper coaxial cables as the preferred transmission medium for electromagnetic waves , thereby revolutionizing terrestrial communications application range from long-distance telephone and data communications to computer communications in a local area network.Inhomogeneous optical fiber formulation