A principle called total internal reflection allows optical fibers to retain the light they carry. When light passes from a dense substance into a less dense substance, there is an angle, called the critical angle, beyond which 100 percent of the light is reflected from the surface between substances. Total internal reflection occurs when light strikes the boundary between substances at an angle greater than the critical angle. An optical-fiber core is clad (coated) by a lower density glass layer. Light traveling inside the core of an optical fiber strikes the outside surface at an angle of incidence greater than the critical angle so that all the light is reflected toward the inside of

Many long-distance fiber-optic communications networks for both transcontinental connections and undersea fiber cables for international connections are in operation. Companies such as AT&T, MCI WorldCom, and Sprint have virtually replaced their long-distance copper lines with optical-fiber cables. Local telephone service providers use fiber-optic cables between central office switches and sometimes extend it into neighborhoods and even individual homes. Cable television companies transmit high-bandwidth TV signals to subscribers via fiber-optic cable.

Optical communications date back to the 1790’s with French engineer Claude Chappe’s “optical telegraph”. Chappe’s system involved a series of semaphores mounted on towers, where human operators relayed messages from one tower to the next. Of course it was superior to hand-carried messages, but by the mid 1800’s it had been replaced by the electric telegraph.

Further work with optical communications had to be put on hold until the continuous wave helium-neon lazar was developed. Researchers then soon found that rain, haze, clouds, and atmospheric turbulence limited the reliability of long-distance lazar links. By 1965, millimeter-wave and laser telecommunications clearly had major technical barriers to overcome. Millimeter waveguides had to be kept perfectly straight in order to maintain a low loss-of-signal. Optical waveguides were also proving to be a problem. Stewart Miller’s group at Bell Telephone Laboratories was working on a system of gas lenses to focus laser beams along hollow waveguides for long-distance communications but the telecommunications company were investing most of their money in millimeter waveguides and shying away from Optical communications.

Nothing more was reported on fiber bundles until 1954, when Abraham van Heel at the Technical University of Delft in Holland, and Harold H. Hopkins and Narinder Kapany of Imperial College in London separately announced imaging bundles. Neither van Heel nor Hopkins and Kapandy made bundles that could carry light far, but their work was still vital to the development of fiber optics. The crucial innovation was made by van Heel with help from American physicist Brian O’Br

Some topics in this essay:
Fiber Optic, WorldCom Sprint, Institute Leningrad, Graham Bell, Wilbur Peters, Peter Schultz, Brian O’Brien, Kao Kao, Telephone Laboratories, Claude Chappe’s, fiber optics, total internal reflection, optical fibers, optical communications, critical angle, internal reflection, total internal, refractive index, van heel, long-distance communications, fiber loss, development fiber optics, light traveling inside, critical angle light, light strikes boundary,