WASHINGTON — Scientists and engineers are racing to develop ways to use light instead of electricity to avoid traffic jams inside computers.
Today's fastest computers employ miles of tiny copper wires to connect multiple data processors packed on silicon chips. Each little ``brain'' — in effect, a miniature adding machine — must exchange information with hundreds or thousands of partners on the same or connecting chips.
The data — symbolized as strings of zeroes and ones — ride the wires in the form of electrical signals, generating heat and wasting energy. Even so, the data can't move fast enough to keep up with the speed of the central processing units.
``The weakest link in the overall capability of the computer is the ability to move information from chip to chip,'' said John Stroman, a computer design strategist at Intel Corp., the big computer-chip maker based in Santa Clara, Calif. ``Moving information around is the biggest limitation on the performance of computers, and it becomes a greater limitation as CPUs become faster.''
Computer scientists think that the solution may be photons, the tiny packets of energy that make up a beam of light. Photons aren't the same as electrons, the fundamental particles of electricity.
The science of photons is known as ``nanophotonics,'' since it deals with infinitesimally small elements at the nanoscale. A nanometer is 1 billionth of a meter; a nanogram is 1 billionth of a gram.
Photons can move data tens or hundreds of times faster than electrons on copper wires, according to Yurii Vlasov, a nanophotonics manager at IBM's T.J. Watson Research Center in Yorktown Heights, N.Y.
"Copper, our traditional interconnect technology, is running out of speed," Patrick Gelsinger, a senior vice president at Intel, wrote in the journal Technology Review.
To direct the data flow, designers have built nanophotonic ``switches,'' which work like miniature railroad yards, routing cyber-traffic among processors.
For example, a Sony Playstation 3 game console has nine processors, known as ``cores,'' on a single chip. Future versions will have tens, even hundreds, of processors per chip.
It will be several years before photons can do much of the work of electrons, but the pace of research is accelerating.
Last week, the Pentagon's Defense Advanced Research Projects Agency, which conceived the Internet, awarded a $44 million contract to Sun Microsystems in Santa Clara, Calif., to design an ultra-high-speed nanophotonic system that can exchange signals efficiently among hundreds or thousands of processing units.
In its request, DARPA said it wanted ``revolutionary advances in science, devices, circuits and computing systems.'' It said it wasn't interested in ``incremental'' improvements.
Earlier in March, IBM announced that it had built what it called the world's tiniest nanophotonic switch, about 100 times smaller than the width of a human hair. The Pentagon also supports IBM's work.
``Scientists have now produced (devices) that control light at breakneck speeds, bringing the vision of all-optical chips closer to reality,'' Michal Lipson, an electrical engineer at Cornell University in Ithaca, N.Y., reported last year in the journal Nature Photonics.
``Within the next five years, practical methods to move information around using light will exist,'' Intel's Stroman said.
ON THE WEB
For more information, go to the Cornell Nanophotonics Group and click on "Research."
