Japan's NTT and NEC reckon they can boost optical network capacities 12x

First tests of manycore fibres hailed as success over oceanic distances

Japanese tech titans NTT and NEC reckon they've proven the performance of a novel fiber optic technology that could increase capacity of submarine cables by a factor of 12.

The two will detail their efforts at next week's Optical Fiber Communication Conference – the world's pre-eminent forum on the topic. On Thursday they teased their presentation with an announcement of tests of using a coupled 12-core multicore fiber over a distance of 7,280km.

As the partners explained, current submarine cables "use single-core fiber, which has a single optical transmission path called a core within a single fiber."

But optical networking boffins are working on multicore fibers that add more paths, without increasing the 0.125 millimeter diameter of each strand. NTT and NEC worked with fibers that packed a dozen cores into that tiny space.

Such fibers have prima facie potential to increase the capacity of optical networks.

If only it weren't for those pesky laws of physics, which mean crosstalk occurs between cores and degrades communications. Over long distances, NTT and NEC admit "it becomes difficult to receive transmitted signals accurately due to the non-uniformity of delay and loss between optical signals."

Fortunately, network boffins already have an approach to fixing this sort of thing. Multiple input multiple output (MIMO) technology – used to separate multiple interfering radio signals – can also be applied to optical networks. NTT and NEC developed an algorithm to bring MIMO to optical networks.

And they made it work in a 7,280km test system that simulated the conditions of a submarine cable.

Modern submarine cables can deploy up to 96 fiber pairs, and offer capacities in the hundreds of terabits per second. Multiplying capacity without requiring larger cables has obvious appeal at any time.

NEC and NTT reckon they could have this tech ready to deploy in the 2030s – just in time to help networkers handle the flood of data expected to be created by the debut of 6G networks. ®

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