Research claims twist of light could be the answer to network capacity deficit caught up with Martin Lavery (pictured), Royal Academy of Engineering Research Fellow at the University of Glasgow, to discuss his project that aims to develop a standardised network technology utilising the ‘twist of light’. Lavery claims this could be part of the solution to the looming fibre network capacity deficit.

Although some of light’s properties, intensity, phase and polarisation, are already used in the backbone of digital communications, Lavery’s research focuses on a lesser realised feature: the spatial degree of freedom of an optical beam: the twist of light.

“The best way to describe what this means in reality is to consider the shape that the beam of a laser pointer makes on a wall- that shape describes the spatial degree of freedom of that beam,” Lavery explains.

The shape of the beam is a key component in this research as it explores how space-division-multiplexing (SDM) can utilise it as a method for multiplexing independent channels into a single channel.

“The shape of a laser beam is defined by a two dimensional transverse amplitude field, where one can spatially vary the local phase and intensity. This technology will work by generating a set of shapes, which we refer to as spatial modes, and these can be differentiated from each other. The communications technology that we aim to develop uses a particular set of modes referred to as orbital angular momentum (OAM) modes. OAM is a particular type of SDM.”

OAM modes are beams which carry an orbital momentum around their axis, essentially meaning they spiral through space. There is potentially an infinite number of these modes, which can form ever tighter spirals.

“We aim to use these spatial modes to give a larger number of multiplexed data streams for use within optical communications in both fibre [as in fibre-optic systems] and free-space, without the need of a waveguide,” Lavery says.

According to Lavery, the fundamental capacity of currently utilised network technologies will have been reached within 20 years’ time as the rate at which the amount of data traffic is growing is showing no signs of slowing down.

“The push for the next generation of communications schemes is on. The amount of information being transferred through our networks is ever increasing. Online services such as iTunes Store, Netflix and Spotify are huge users of network bandwidth, where Netflix alone accounts for around one third of all the internet traffic in USA. This is only set to increase over the coming years.

“The use of OAM could overcome this limit by increasing a fibre’s capacity. This is a key driving force behind the development of these next-generation technologies- including OAM-based systems- and the reason SDM is a current hot research topic in the field of optical communications.”

Indeed Lavery and his team are not the only ones exploring the possibilities of SDM. Researchers at Vienna University in Austria recently demonstrated how beams of light forming a corkscrew shape could carry data over a distance of more than three kilometres.

There are others too who are focusing on SDM research but Lavery doesn’t see the different studies are in competition with each other. “SDM is becoming a burgeoning field of study, with a few teams focusing different forms of multiplexing. The field is supportive of each other’s advances.

“The choice of which particular mode will become the industry standard is a complex one. My feeling is that we will see many different forms of SDM being implemented, and the choice will depend on the particular environment the system is being designed for.

“Networks are large and sprawling, and the system that works best in a server farm my not be best for broadcasting the latest TV show being distributed on streaming services.”

Talking of industry standards and mainstream availability, Lavery says the groundwork has been laid for some emerging technologies on which he intends to build on. “The key factor in the commercial viability of OAM, or other forms of SDM, is the development of tools for the multiplexing and de-multiplexing of channels in systems that use this new technology.

“The Royal Academy of Engineering is now supporting my efforts at Glasgow University to develop a complete tool kit that will help in the integration of OAM multiplexing into commercial optical communications networks. I think we could have a commercialised product maybe in five years’ time.”

So far, the project has received support from IT chip vendor Intel and fibre system vendor Corning, whose role is largely to provide guidance and feedback from the industry point of view.

It will be interesting to see how things will develop in the SDM research space, and if we can really see this becoming commercial reality in the next five years. It is certainly true that capacity is only going to become a bigger problem in the coming years, and any new technology to alleviate the situation should be well received. However, the technology must both work and make commercial sense.

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