Computing with Light

ORIGINAL: MIT Technology Review

David Zax

December 10, 2012

A breakthrough from IBM could signal a future for computing.

This image shows a falsely-colored integrated optical and electrical circuit. The blue wires carry optical signals and the yellow wires carry electrical ones.

IBM announced what it called a technological breakthrough today in San Francisco. The company verified in a manufacturing environment the feasibility of using light instead of electrical signals to transmit information. IBM had proven the concept of such technology, called “silicon nanophotonics,” back in 2010, but this announcement, following a decade of research, nudges the field towards commercial applications.

In its 2010 announcement, IBM described the invention succinctly: a chip that “integrates electrical and optical devices on the same piece of silicon, enabling computer chips to communicate using pulses of light (instead of electrical signals), resulting in smaller, faster and more power-efficient chips than is possible with conventional technologies.” The development forms a part of IBM’s “Exascale computing program,” which wants to build a supercomputer than can perform a million trillion calculations (a so-called “Exaflop”) in a second. IBM says the chip was made using a 90 nanometer manufacturing process, and that the optical data can travel through the chip at 25 Gigabits per second.

Basically, IBM hopes this will solve the problem that we are creating and transmitting data faster than our hardware has been able to keep up with. Silicon nanophotonics, says IBM, will help industry “keep pace with increasing demands in chip performance and computing power.” As one of the researchers, Dr. Solomon Assefa, explained: “For our computer servers to keep up with this growth, so that we can actually make sense of the data through analytics and so forth, we need to have a new technology.”

Why compute with light, rather than electrons? As TR explained in 2011 (see “Light Chips”): “The speed of supercomputers is constrained not by processing power but by limits on how fast data can travel down the electrical wires that link up different chips. Light signals move significantly faster than electrical ones, so using them could remove that bottleneck.” Reports today also pointed out that transmitting via light allowed further distances of data transfer while minimizing risk of lost data.

Again, today’s announcement has more to do with the process of fabricating the technology, which had already been demonstrated. IDG News Service sums it up well: IBM has shown that it’s possible to “bake optical circuitry into silicon processors using existing fabrication techniques, which could set the stage for radically faster and lower-cost computer communications.” The BBC explains that many data centers already use optical cables to shuttle around data, but they’ve had to have expensive equipment to convert photon-data into electron-data.

IBM presented the breakthrough at the 2012 IEEE International Electron Devices Meeting.