Hair-thin fibers of ultrapure glass are now transmitting voice, data, and video communications in many parts of the globe in the form of digital signals emitted by semiconductor lasers the size of a grain of salt. Source: PLG Group
ORIGINS OF THE INFORMATION SUPERHIGHWAY
Ten years ago, the information superhighway could not have been built. Many of the core technologies essential to the convergence of computing and communications--a conjunction at the heart of the information superhighway--were simply not ready. The discoveries that initiated or made these technologies possible go back even further--before anyone dared to dream of a world in which scientists could collaborate across continents, in which every school could be connected to the great libraries and museums, and in which ordinary citizens could tap a wealth of digital services and entertainment from their homes.
The true origins of the information superhighway, in fact, include fundamental research on the physics of surfaces in the late 1940s that led to transistors, obscure university work on microwave oscillators in the early 1950s that led to lasers, and a speculative suggestion in an academic journal in the mid-1960s that led to optical fibers. Such research, if proposed today, would be hard to distinguish from hundreds of similar basic research proposals. Yet it produced the seeds of a revolutionary technology that is likely to transform homes and workplaces alike.
Consider one thread in this complex story, that of optical fibers. The idea that laser light could be transmitted over long distances in a glass fiber--and hence used for communications--can be traced to a 1966 article in a scientific journal. The first fibers were relatively crude; they broke easily and defects or impurities in the glass scattered or absorbed enough of the light signal that it couldn't travel very far. But basic research on the chemistry and thermodynamics of glass and on the scattering of light in liquids (glass can be thought of as a cooled liquid) led to steady improvements--purer glasses that reduced losses, for example, and epoxy coatings that made the fibers more flexible and resistant to corrosion. In 1970, Corning Glass Works demonstrated a fiber that could transmit a light signal with losses of only 1 percent per kilometer--a big advance at the time, but not good enough for commercial systems.
Today's fibers have losses of 100-fold less, reduced almost to the theoretical limit, and the result has been an explosion of optical communications. Optical fibers now carry most U.S. long-distance telecommunications and the total traffic over fibers is 1,000 times greater than a decade ago.
But the fiber story is far from finished. Fundamental research into the properties of rare earth elements, such as erbium, has led to a new wave of developments that are transforming fibers from passive to active devices with even greater carrying capacity. When fibers are doped with erbium and powered by a semiconductor laser, they can amplify an optical signal. Spliced directly into a fiber cable, these fiber amplifiers will soon begin to replace the regenerating stations that now detect, amplify, and retransmit optical communications signals every 30 to 100 kilometers. Since the comparatively slow electronic components of regenerating stations are the principal bottlenecks in today's long-distance networks, this change to an all-optical technology will increase the capacity of long-distance communications systems by as much as 100-fold.
The process is a continuing one. Just as commercial deployment of the information superhighway is harvesting earlier investments in the creation of basic knowledge, so the technologies of tomorrow and the commercial competitiveness that goes with them will stem from the science of today.
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