Twisted light the answer to slow broadband speeds: Australian scientists
Scientists at the Royal Melbourne Institute of Technology says they’ve invented fibre optic technology that could increase the bandwidth of the internet by a factor of 100 or more.
The technology harnesses a quantum property of light to vastly increase the number of laser beams that can simultaneously travel along a fibre optic cable. It was outlined overnight in the peer-reviewed Nature Communications science journal.
The quantum property, known as the Orbital Angular Momentum (OAM) of light, was identified more than a decade ago as a potential way to send an almost unlimited number of data-carrying laser beams through a single glass fibre, simultaneously.
But RMIT scientists say they’ve now figure out how to miniaturise the technology that transmits and then receives light that’s had its OAM manipulated. What previously took an unfeasibly large piece of technology “the size of a dinner table” can now be put into a single, tiny chip that could be commercialised and revolutionise the internet in just a few years, the scientists say.
Current fibre optic technology doesn’t simply send one beam of laser light down a glass fibre to transmit data. Using a technique known as Wavelength Division Multiplexing, it simultaneously sends laser beams of multiple different colours down the fibre, with each colour carrying a stream of data. A fibre carrying red, green and blue light, for instance, would have triple the data bandwidth of a fibre just carrying red light.
Another technique, known as Polarisation Division Multiplexing, uses light waves that are operating on a variety of planes along the fibre – think of the ABC symbol upright, or lying flat, or at some angle in between – to further multiply the capacity of optical fibre.
The latest technique uses yet another property of light, its OAM, to further differentiate different beams of light, further increasing the number of signals that can be sent and received at once.
Put very simply, the orbital angular momentum of light measures how it twists at it’s travelling through space, its twists being vaguely analogous to the way DNA twists in its famous double-helix fashion.
RMIT scientist say they have created a chip that can induce and then later measure as many as 100 different rates of twisting, increasing fibre optic cable capacity 100-fold.
But, as befits anything shaped liked a helix, there is a twist with the new technology. The fibre optic cables that have already been layed around Australia aren’t designed to carry information about the angular momentum of light, and new cables with a modified glass core would probably need to be laid, he said.
Also, nobody has yet figured out how to use OAM multiplexing over the long distances that networks such as the National Broadband Network would require, Professor Gu said, though the distances were getting farther with each passing year.
While developments such as this do demonstrate that fibre cables are much more “future proof” than the copper cables that the Coalition Government insisted upon for the National Broadband Network, they would do little to ease congestion on the NBN in the short or medium term, said Phillip Britt, managing director of the internet provider Aussie Broadband.
When Aussie Broadband customers experience congestion on the NBN, it’s related to the copper ADSL and coaxial cables that run from NBN nodes to houses, and not related to the fibre optic backbone of the NBN, Mr Britt said.
What would have a bigger impact than twisting the light on the NBN’s fibre optics cables would be to replace the aging copper with ordinary optical fibre. Even if the fibre only went to the curb outside of customers’ houses, and not all the way to the house as the Labor government had originally proposed, that would still be ten-times faster than the current NBN speeds most customers are limited to, he said.
Such fibre would have plenty of bandwidth, far more than customers could use for many years to come, even before it got the added twists, he said.
For its part, the NBN said it had enough capacity on its fibre optic backbone, without the need for further technological advances.
“There is plenty of capacity on our Transit Network but we continue to closely monitor this to ensure we have the right upgrade path in place to increase capacity as the need arises,” an NBN spokesperson said.
“Recently we switched on a major upgrade to double capacity on high-traffic links in the 60,000km fibre optic backbone network. The upgrade means NBN Co can increase maximum capacity on its transit network from 9.6 Terabits per second (Tbps) to 19.2Tbps per fibre link, which will help meet the broadband needs of homes and businesses into the future.”
Whether the new OAM multiplexing technology would ever be adopted on the internet would depend on a number of factors, the NBN spokesperson said, including how widely it was adopted by equipment manufacturers.
“New communications technologies are continually being tested in labs many years in advance of being commercialised. They require widespread acceptance from equipment manufacturers and network operators before they are ready for operational deployment.
“NBN Co regularly tests new technologies as part of our upgrade path to ensure we are prepared for future demand and continue to offer the best experience for consumers and businesses. We have demonstrated this already with the deployment of new technologies like (fibre to the curb),” NBN said in a statement.
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