Basic Research Remains Vital

In early fiber-optic systems, the amplifiers for regenerating a weak signal constituted a bottleneck. Although optical devices could be used to detect an incoming laser signal, some sort of electronic circuitry was needed to convert it to electric current, amplify the current, and then drive a new laser to recreate the optical signal. This limited the system to the capacity of the electronic amplifiers, which was considerably less than the potential capacity of the lasers and optical fibers.

But in 1985, at England's University of Southampton, physicist S. B. Poole discovered a solution. Adding a small quantity of the element erbium to the glass used in optical fibers would make it possible to build an all-optic amplifier. A short strand of erbium-doped glass, spliced into the main fiber, would receive energy from an external source and act as a laser in its own right, amplifying a weak optical signal without using electronics.

Poole's colleagues at Southampton, David Payne and P. J. Mears, and Emmanuel Desurvire at Bell Laboratories, proceeded to turn the discovery into practical and effective fiber-optic amplifiers. In 1991, investigators at Bell Laboratories demonstrated that an all-optic system would have a carrying capacity about 100 times that then achievable with electronic amplifiers. In short order, both European and American communication firms installed all-optic cables across the Atlantic, and a Pacific cable entered service in 1996.

Clearly, progress has been remarkable and rapid. Impressive as these accomplishments are, even more dramatic advances are on the horizon. Although today's fiber-optic systems serve as trunk lines, carrying large numbers of voice and data channels between central telephone stations, industry specialists speak wistfully of the "last mile"--from the central station to your home. Today's telephone system spans that last mile with conventional copper-wire equipment, which provides good voice connections but is still inadequate for carrying large quantities of high-speed data.

High-speed data lines for that last mile are available, and many businesses have them, but they are generally more expensive than is practical for home use today. Whatever new technology turns out to provide the last crucial link from individuals to the rest of the world, the research that gives rise to it will have come from scientists who probe beneath the immediate needs of any given industry, investigating seemingly unrelated processes to understand the fundamental nature of the world.

August 20, 2011

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