Licklider’s Intergalactic Computer Network - The Computing Universe: A Journey through a Revolution - page 217

B.10.21. Optical fiber pioneers from Corning Glass Works: from left to right, Donald Keck, Bob
Maurer, and Peter Schultz. The three developed the first low-loss optical fiber in 1970 after hearing
of Charles Kao's goal of a loss of only twenty decibels per kilometer, equivalent to 1 percent of the
light remaining after transmission through a one-kilometer glass fiber.

using chemical vapor deposition ( B.10.22 ). This is a chemical process that deposits
a thin coating on the silica and allows the creation of preforms with a specific
refractive index profile. Simultaneous publications from the Southampton
group and Bell Labs then gave details of a feasible method of manufacturing
doped optical fibers. Using this method, Gambling and Payne were able to make
fibers with a loss of only 2.7 decibels per kilometer. Although British Telecom
became the first phone company to commit to optical fiber, it was the decision
of MCI Communications Corporation to use optical fiber to build a nationwide
long-distance communication network in the United States that really opened
the floodgates. In 1982, MCI ordered one hundred thousand kilometers of fiber
from Corning and took on the battle with the dominant AT&T. By the mid-
1980s, the U.S. government had loosened many restrictions that limited com-
petition in the long-distance telephone industry in the United States, creating
a very competitive market for fiber networks.
The last piece of the puzzle arrived in 1987 when Payne and a team at the
University of Southampton discovered a way to amplify the optical signal in the
fiber. Up to then, when the optical signal grew too weak for further transmis-
sion, the signal had to be converted from optical to electrical, amplified, and
converted back again to an optical signal. By adding a small amount of the ele-
ment erbium to the core of the fiber, Payne and his colleagues at Southampton
demonstrated that the signal could be amplified using a semiconductor laser as a
pump , a device that boosts or amplifies a signal ( Fig. 10.24 ). The first commercial
product was produced in 1990 by Pirelli in the United Kingdom, in collaboration
with the Southampton team. The first transatlantic fiber cable had a capacity of
eight hundred telephone circuits, and the cost per circuit was $30,000; only ten
years later, transatlantic cables with fiber amplifiers had a capacity of six hun-
dred thousand circuits at a cost per circuit of only $500. In this way, fibers and
erbium-doped fiber amplifiers (EDFAs) have revolutionized telecommunications
and computer networks. Kao's original vision for optical fiber communications
has come true: “If you really look at it, I was trying to sell a dream. . . . There was
very little I could put in concrete to tell these people it was really real.” 35
One postscript to this story is the curious fact that although the United
States led the world in developing lasers, AT&T and Bell Labs virtually ignored
the idea of fiber-optic communications. Equally surprising is how a small uni-
versity research group at the University of Southampton with very limited
funding not only competed with all the major telecommunication research
laboratories but also made a string of fundamental discoveries. Payne believes

Fig. 10.24. Schematic representation of
the working of the erbium-doped fiber
amplifier (EDFA).