Twisted Light Sends Data Through Optical Fiber for First Time

For the first time beams of “twisted” light have been used to transfer data through optical fibre.  A team of researchers from Boston University and University of Southern California succeeded in transmitting 1.6 terabits per second using one kilometer of optical fiber. Last June, a team of researchers transmitted data through the air at 2.56 Tb/s using twisted light, but this is the first time the method has been used to send data through optical fiber.

Twisting light means photons have a quantum characteristic called orbital angular momentum (OAM). Photons with OAM have electric and magnetic fields that corkscrew rather than oscillate in a plane. There are a theoretically infinite number of OAM values, and multiple beams having different orbital angular momentums can occupy the same fiber, allowing  more data to be transferred.

Before this breakthrough, using twisted light technology in optical fiber was impossible. But with a new optical fiber developed by Siddharth Ramachandran, a professor of engineering at Boston University, twisted light beams can now safely reach their destinations.

"For several decades since optical fibers were deployed, the conventional assumption has been that OAM-carrying beams are inherently unstable in fibers," said Ramachandran. "Our discovery, of design classes in which they are stable, has profound implications for a variety of scientific and technological fields that have exploited the unique properties of OAM-carrying light, including the use of such beams for enhancing data capacity in fibers."

With data high in demand, the number of wavelengths we can use to increase bandwidth has started to reach its limits. Researchers hope that OAM will allow bandwidth to expand even further.

Twisted light technology isn’t only for optical wavelengths. Researchers in Italy and Sweden were successful in applying OAM to radio waves. They were able to transmit two “twisted” radio beams a distance of 442 meters by bending a dish antenna. But some radio communication scientists aren’t convinced that this will actually increase capacity. Some argue that OAM radio frequencies mimic existing multiple input multiple output (MIMO) technologies.

Image: David Steinvurzel; background image © INMAGINE Limited

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