AT&T Bell Labs scientists became interested in lightwave communication in the
mid-1960s, when it became apparent that lightwaves had an enormous
capacity for carrying information and were immune from electrical
interference. Advances in lasers, light-emitting
diodes, repeaters, connectors, photodetectors and glass fibers in the
following decades - and the realization that they could be fabricated and
installed as integrated components - led to the installation of the first
lightwave system in an operating telephone company in 1977.
This installation was the world's first lightwave system to provide a full range of telecommunications service - voice, data, and video - over a public switched network. The system, extending about 1.5 miles under downtown Chicago, used glass fibers that each carried the equivalent of 672 voice channels.