Fiber optic

Fiber optics is a technology which uses light to carry data over a communication link. The light is usually produced by a semiconductor laser now, and is carried over a special medium, optical fiber (the source of the name) to a detector back at the far end, which converts it back into electrons.

Optical fiber consists of very clear glass, drawn out into a very thin fiber. Light introduced at one end effectively bounces off the walls of the fiber (which it meets at a shallow angle) as it travels down it. The fiber is actually former of concentric layers with a different index of refraction; as a photon traverses the layers, its path is bent around and it winds up reflected back into the body of the fiber.

Most wide-area networks are now built out of fiber-optic links.