A New Twist That Could Speed the Internet

by Evan Applegate, courtesy BusinessWeek

Photograph by Tobias Ackeborn/Getty Images

Photograph by Tobias Ackeborn/Getty Images

What strands of copper were to the 19th century, strands of glass are to the 21st. Since their introduction in the 1980s, fiber-optic cables have become the backbone of the digital age. The amount of data they deliver has increased a thousandfold in that time, but we’re brushing theoretical limits on fiber-optic speed.

Researchers at Boston University and the University of Southern California, in collaboration with Danish optics company OFS Fitel, with funding from Darpa, may have just raised those limits. The team’s fiber-optics experiments have transmitted data at 1.6 terabits per second, more than 15 times the speed of cables in high-end data centers—and fast enough to download four dual-layer Blu-ray discs in a few heartbeats.

Sending larger amounts of information down a fiber line at once is a problem of space. More data requires more light beams to pass through the line, and there’s only so many beams you can cram in before they interfere with each other and scramble the data. According to a paper in Science, the researchers added more light by twisting the beams into a corkscrew shape, exploiting a property of light called orbital angular momentum (OAM).

If you think of the fiber-optic line as a candy cane, the OAM light beam would be the stripe. It’s been tried before, but until now has always scrambled the other light beams. To prevent that, BU professor Siddharth Ramachandran designed a cable that slows light passing through the outer layers, ensuring that the coiling OAM beams won’t interfere with one another. “Our discovery has profound implications for a variety of scientific and technological fields,” says Ramachandran.

The test cable was only a little more than a half-mile long, so for now OAM beams are better-suited for data centers than the undersea cables that thread between continents. Combined with other techniques of boosting fiber bandwidth, though, the technology has the potential to deliver screaming Internet speeds beyond the lab. Soon, the Internet might turn on a twist.

Applegate is a graphics editor for Bloomberg Businessweek. Follow him on Twitter @evanapplegate.

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