November 8, 2013

Tiny Laser Transmits Data at Record Speeds

Tiffany Trader

In the age of big data and cloud computing, fast and accurate data transfer is more important than ever. University of Illinois scientists address the network bottleneck.

Scientists at the University of Illinois have figured out a way to transmit error-free data over fiber optic networks at 40 gigabits per second, a US record according to a press release.

With the computational arms race pushing top machines into petascale territory and beyond, processor speeds have advanced faster than transfer speeds. The lag in transfer speeds creates a bottleneck that stymies applications. Even the fastest supercomputer can’t make a file download any faster than the network allows.

The twin technologies of big data and cloud computing – which rely on moving data from point a to point b quickly and accurately – have put a spotlight on this compute-network disconnect.

“Information is not useful if you cannot transmit it,” said Milton Feng, the Nick Holonyak Jr. Chair in Electrical and Computer Engineering. “If you cannot transfer data, you just generate garbage. So the transfer technology is very important. High-speed data transfer will allow tele-computation, tele-medicine, tele-instruction. It all depends on how fast you can transfer the information.”

Feng and his colleagues demonstrated the tiny, fast device and published the results in the journal IEEE Photonics Technology Letters.

The researchers describe a new breed of laser devices called oxide VCSELs (vertical cavity surface emitting lasers), which transmit data over fiber optic cables using light signals. They are known for being faster and more energy efficient than traditional electrical cables.

“The oxide VCSEL is the standard right now for industry,” Feng said. “Today, all the optical interconnects use this technology. The world is in a competition on how to make it fast and efficient, and that’s what this technology is. At the U. of I., we were able to make this technology the fastest in the U.S.”

Compared to the so-called consumer Internet, which can reach speeds of about 100 megabits per second, oxide VCSEL technology at 40 gigabits per second is 400 times faster. And because of its small size, the device uses 100 times less energy than electrical wires.

Currently these oxide VCSELs operate at room temperature, but the Illinois team is working to make them compatible with the higher temperatures that are characteristic of datacenters. Feng believes the laser device could be coaxed to perform at 60 gigabits per second before encountering certain inherent limitations. But when that happens, he’s counting on another cutting-edge device, the transistor laser, to carry the performance torch forward.

Update – Editor’s note:

After receiving a question about how this technology is better than the standard 40G and 100G Ethernet that is currently available, researcher and report co-author Fei Tan kindly provided a thorough explanation, as summarized in the following paragraph:

The direct modulation based short range (< 100 meter) 40G (100G) ethernet employs 4 (10) lasers to achieve 40 (100) Gb/s data transmission. As compared with the standard 40G ethernet, our VCSEL technology employs only a single laser device. Hence our VCSEL technology is more energy efficient, simpler in driver circuits, and more cost effective. In addition, our VCSEL technology not only provides 40 Gb/s error-free data transmission, but also provides an ultralow laser RIN, which is essential in achieving and maintaining error-free data transmission through the optical fiber link.

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