Using light instead of wires to send information between the computer cores of a computer chip can be 100 times faster and use 10 times less power than wires. The new IBM technology aims to enable a power-efficient method to connect hundreds or thousands of cores together on a tiny chip by eliminating the wires required to connect them.
UPDATE: Joel Hruska and Chris Lee of Ars Technica discuss the potential and the specific benefits of this technology and when it will appear. Probably 5-15 years with redesign of the chip to accomodate.
At present, the technology is too big and has no supporting on-chip light source. That said, the long-term potential for such a technology is good. Chip-level optical routing would allow cores to communicate much faster than even the best wired connection (IBM estimates its nanophotonic technology would be 100 times faster) and would almost certainly eliminate any bandwidth-related bottlenecks within a single core.
IBM’s optical modulator performs the function of converting a digital electrical signal carried on a wire, into a series of light pulses, carried on a silicon nanophotonic waveguide. First, an input laser beam (marked by red color) is delivered to the optical modulator. The optical modulator (black box with IBM logo) is basically a very fast “shutter” which controls whether the input laser is blocked or transmitted to the output waveguide. When a digital electrical pulse (a “1” bit marked by yellow) arrives from the left at the modulator, a short pulse of light is allowed to pass through at the optical output on the right. When there is no electrical pulse at the modulator (a “0” bit), the modulator blocks light from passing through at the optical output. In this way, the device “modulates” the intensity of the input laser beam, and the modulator converts a stream of digital bits (“1”s and “0”s) from electrical input pulses into pulses of light. Credit: IBM
The breakthrough — known in the industry as a silicon Mach-Zehnder electro-optic modulator — performs the function of converting electrical signals into pulses of light. The IBM modulator is 100 to 1,000 times smaller in size compared to previously demonstrated modulators of its kind, paving the way for many such devices and eventually complete optical routing networks to be integrated onto a single chip. This could significantly reduce cost, energy and heat while increasing communications bandwidth between the cores more than a hundred times over wired chips.
The report on this work, entitled “Ultra-compact, low RF power, 10 Gb/s silicon Mach-Zehnder modulator” by William M. J. Green, Michael J. Rooks, Lidija Sekaric, and Yurii A. Vlasov of IBM’s T.J.WatsonResearch Center in Yorktown Heights, N.Y. is published in Volume 15 of the journal Optics Express. This work was partially supported by the Defense Advanced Research Projects Agency (DARPA) through the Defense Sciences Office program “Slowing, Storing and Processing Light”.
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