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A light twist

A new spin on fiber optics packs hefty data into a small space

By
6:04pm, July 10, 2013

Computers see data as strings of 1s and 0s. Those numbers can be encoded in light beams that travel through fibers. Researchers recently designed a new fiber that can carry even more data when light beams are given a little twist. Credit: Courtesy of David Steinvurzel; background image © INMAGINE Limited

Modern life depends on data that moves quickly over large distances, whether we’re on mobile phones or online. But too much data can slow the flow. That’s why engineers have been developing clever ways to deliver big data at fast speeds. And a new type of fiber-optic cable may do just that.

It moves multiple streams of data at high speeds without losing information, engineers reported in the June 28 issue of Science.

“It’s like having more fibers without actually laying more fibers,” Andrew Weiner told Science News. Weiner, a physicist at Purdue University in West Lafayette, Ind., did not work on the new technology.

Fiber-optic cables contain bundles of thin, flexible glass fibers that transmit light. Nothing travels faster than light. So companies that offer customers lightning-fast access to the Internet use these cables to move data. Light has its limits, however. Like rush hour on a crowded highway, too much data in a cramped cable leads to congestion.

In the past, engineers have developed other ways to cram more data into each beam of light traveling through some fiber in a cable. They’ve also found ways to send multiple streams, for instance by using light beams of different colors. But in the near future, even those fixes won’t keep up with the growing data demands of users. And it’s expensive to install additional cables.

“We’ve gotten to the point where the [telecommunications] community has been asking what else we can do,” Siddharth Ramachandran told Science News. Ramachandran, a physicist at Boston University, helped design the new cable.

He and his coworkers developed a way to keep multiple beams of light from mixing in a single fiber. They built a 1.1-kilometer (about 0.7-mile) fiber treated with chemicals that change the speed of individual light beams passing through. That change keeps beams from mingling because they’re moving through the fiber at different speeds.

The team then gave the light beams a little twist — literally. For comparison, imagine a shoelace is a beam of light. You can lay the shoelace out so that it’s straight and flat. But you can also hold one end and twist the other. Light beams can travel in those ways, too: straight or with a twist as they move through a cable. (This twisted shape is known as a helix.)

Ramachandran and his coworkers found a way to twist individual beams. One beam might be twisted in one direction. Another might be twisted in a different direction. Yet another may have more twists. Imagine you lined up 100 shoelaces. If they were all flat, they’d look the same and it would be hard to tell them apart. But if you gave each one its own special twist, you could always tell them apart.

The researchers sent light beams with different amounts of twist sailing through the new fiber. They then tested different colored light beams twisted in one of two ways. These early experiments showed that the fiber delivered the information fast, and without any mix-ups.

The researchers don’t know if longer fibers will work as well. But they note that the size they tested could be useful for companies like Facebook and Google. That’s because these companies rely on storing and sending vast amounts of data over short distances.

Power Words

fiber optics The use of thin, flexible fibers of glass or other transparent solids to transmit light signals, chiefly for telecommunications.

physics The scientific study of the nature and properties of matter and energy.

engineering The use of math and science to solve practical problems.

helix An object with a three-dimensional shape like that of a wire wound uniformly in a single layer around a cylinder or cone, as in a corkscrew or spiral staircase.

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