December 20, 2006 10:00 PM PST

IBM slows down light signals in chips

IBM is making light take the long way 'round.

Researchers at Big Blue have published a paper demonstrating how optical signals--photons that represent data--traveling within a microprocessor can be delayed, a key element in developing chips that can relay signals with optical fiber.

Delayed optical signals

Intel, IBM and relative newcomers such as Primarion and Luxtera are trying to devise ways to replace the metal cables that connect chips inside computers, as well as wire connections inside chips, with optical components. Optical technology consumes much less energy. Plus, it doesn't generate heat, and it can transfer signals faster than metal wires.

Designers often refer to optical component design as a black art that defies easy mastery. Currently, optical components are typically made out of "exotic" materials such as gallium or indium compounds.

Ideally, companies experimenting in this arena want to make these chip-size optical components out of silicon wafers to keep the cost low. Among other parts, Intel and others have produced silicon lasers and waveguides--structures that guide waves, whether electromagnetic, light or sound. But these companies have not yet integrated the lasers and waveguides into commercial products.

IBM's latest contribution is slightly different than many of the earlier breakthroughs. It seeks to slow down the flow of signals so the transfer of information remains controlled and synchronized.

To delay the signals, the light passes through a "microring resonator," which is a waveguide looped into several circles rather than a straight line. Because the light has to travel much farther than it would if the waveguide directly connected two points, the data traffic can be buffered.

The circular design also means that the waveguide is small enough to integrate into a chip. Because of all of the traffic loops, roughly 10 bits of optical information can travel simultaneously within a space, taking up 0.03 square millimeters.

See more CNET content tagged:
IBM Corp., signal, laser, component, Intel


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Slowing down light???
On the surface, it sounded like IBM was doing something special by actually slowing down the speed of light. Maybe I'm out of my league here, but it doesn't sound like they've done that at all. Rather, they've just made the light travel a longer distance to "simulate" it actually traveling slower.

If I drive my car at 55 in a straight line to grandma's, then drive home at 55 but use every cloverleaf I find, of course it will take me longer.
Posted by john.breen (27 comments )
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Slowing down light is easy,
What most people think of as the speed of light is the speed of light in a vacuum. If light is refracted though any transparent material it is slowed down. If you refract light through caesium gas light is sped up.

What IBM did is far more impressive than slowing down the speed of light.
Posted by ralfthedog (1589 comments )
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Technology, not Physics
This story isn't about a breakthrough in Physics (slowing down
the speed of light), it's about a breakthrough in Technology
(effectively slowing down light signals).
Posted by Marc Myers (51 comments )
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It's a matter of timing
Kind of like a traveling wave tube, that can speed up a wave front, using a light waveguide it conduct data bits would allow for critical timing in buffering data and kind of like cacheing data until it is needed by another device, or the device is ready to accept it.
Posted by mjd420nova (91 comments )
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