Joyce Poon Modulates Light for Energy-Efficient Data Centers

Optical communications could be a boon for data centers, reducing electricity use and heat buildup by replacing electronic signals with light signals. But the technology has been cost-effective only over distances of a kilometer or more, and using it in data centers would mean sending signals mere meters or centimeters. Joyce Poon may have solved the problem by creating new optical modulators with microscopic loop-the-loops through which light can shuttle data between servers and even from chip to chip within a single server.

To make light-based data communications work over short distances, Poon, an assistant professor of electrical and computer engineering at the University of Toronto, knew she needed to come up with a much smaller version of an optical modulator, a device that converts an electronic signal into an optical one. She designed tiny rings that can be built onto computer chips. When laser light is sent into a ring, it races around the ring over and over before a bit of it emerges through a waveguide at the bottom. The trick was to control how much light came out. Other researchers working with micro-rings have tried to do that by adjusting the properties of the ring, in order to alter the length of the light’s path or the amount of light the ring absorbs. Poon realized she could leave the ring alone and simply control the gateway between the ring and the rest of the chip.

The resulting optical modulator can be both faster and more efficient. With a team from IBM, Poon is working to create a version that is competitive with today’s optical data rates.

The jump to optical data transmission in servers can’t come soon enough. Data centers consumed at least 200 billion kilowatt-hours’ worth of power in 2010, and the proliferation of smartphones and cloud storage is only going to push that higher, driving up costs and the risk of heat-related outages.