As more and more data-hungry services, like audios and videos, gain popularity, the volume of data traffic traversing the world's optical fibre networks is also expected to grow by more than 40 percent per year. And in order for the future networks to cope up with the growing traffic and handling the applications that are set to grow more, the technologies that power long-haul optical networks need to go under a major upgrade.
Some of the key groundwork for this has now been laid by engineers working in SAFARI (Scalable And Flexible optical Architecture for Reconfigurable Infrastructure), an EU and Japanese collaborative project. The EU side was led by project co-coordinator Toshio Morioka of the Technical University of Denmark, whilst the Japanese side was led by project co-coordinator Dr. Yutaka Miyamoto of NTT Corporation, Tokyo.
The chief metric in need of vast improvement in laser-based Optical Transport Networks (OTNs) is data throughput—the number of bits of data per second they can carry encoded in laser beams. Today's individual optical fibres operate at several tens of terabits per second—but that is not going to be enough. To support the huge capacity demands coming up in the future, far higher capacity transport networks with fibre speeds scalable to petabits per second will be needed. To make this happen, the SAFARI collaborators have innovated on a number of fronts, in terms of both overall network control and light-carrying components, to produce building blocks for future OTNs that can boost their speeds from today’s 1013 (tens of terabits) to 1015 (petabits) per second.
SAFARI's first innovation was to develop super-dense multicore optical fibres with 30, 32 or 37 light-carrying cores inside them rather than the single core used today. What allowed them to create this world-record number of cores, says Morioka, was working out a way to stop light from one core leaking into another and causing signal interference that would negatively impact bandwidth.
When traversing large distances of 1000 km or more, light travelling in this complex matrix of cores loses power and has to be boosted at regular intervals. To do this in a power-efficient way, the project team developed multicore optical fibre amplifiers, based on erbium and ytterbium, which can be spliced directly into the new multicore fibre, allowing loss-compensated transmission to be made over long distances. The team has broken core-count records, and enabled a reduction of power consumption for optical inline amplifiers, enhancing the power efficiency of future OTNs.
However it is not all about the waveguides: telecoms carriers also need to be able to dynamically allocate and optimize extra network resources, while maintaining quality, to meet spiking demand—like a whole nation wanting to watch the finale of 'Game Of Thrones' on streaming video at once, for instance. So NTT developed programmable optical hardware that allows highly flexible, scalable and adaptive OTNs to be constructed.
A SAFARI testbed was developed and built comprising of novel optics that allow for adding, blocking, passing or redirecting of light beams in a fibre network under software control. This programmable network can be adaptively controlled and managed in response to the actual traffic demands by a central entity. The OTN's programmability has also been tested in experiments designed to ensure that it is suitable to meet the needs of multicore fibre transmission in the networks of the future. With SAFARI not set for deployment until the mid-2020s there is no immediate commercialization planned for the technology. But thanks to this successful research project, the European and Japanese telecoms sectors will be ready when the time comes.