B-4-k- FIBER OPTIC COMMUNICATIONS
The use of optical means (e.g., smoke and fire signals) for the transmission of information dates back to prehistoric times.
However, no major breakthrough in optical communications was made until 1966, when K.C. Kao and G.A. Hockham of Standard Telephone Laboratories, U.K., proposed the use of a clad glass fiber as a dielectric wave guide, the laser (acronym for light amplification by stimulated emission of radiation) had been invented and developed in 1959 and 1960.
Kao and Hockham pointed out that the attenuation in an optical fiber was due to impurities in the glass, and the intrinsic loss, determined by Rayleigh scattering, is very low.
Indeed, they predicted that a loss of 20 dB/km should be attainable, This remarkable prediction, made at a time when the power loss in a glass fiber was about 1000 dB/km, was to be demonstrated later. Nowadays, transmission losses as low as 0.2 dB/km are achievable and new experimental WDM techniques are multiplying fiber capacity 120 times.
The spectacular advances in microelectronics, digital computers, and light-wave systems that we have witnessed to date, and that will continue into the future, are all responsible for dramatic changes in the telecommunications environment; many of these changes are already in place, and more changes will evolve as time goes on.