Nokia, Facebook take 250Gbps ride on trans-Atlantic subsea cable

Nokia and Facebook have claimed to more than double the capacity of existing fibre on a 5,500km trans-Atlantic subsea cable in tests with Nokia Bell Labs' new probabilistic constellation shaping (PCS) technology.

The companies collaborated in order to increase capacity capabilities of subsea fibre and enhance the support for telecommunications infrastructure coping with surging bandwidth-hungry applications, such as video and virtual reality.

According to Nokia, the field trials of new optical digital signal processing technologies, which used shaped 64-QAM, over the subsea link between New York and Ireland achieved a record spectral efficiency of 7.46 b/s/Hz and increased the stated capacity of the system by almost 2.5 times. It indicates the potential to upgrade this cable to 32Tbps per fibre in the future.

The test also included a successful 11,000km round trip submarine transmission using shaped 64-QAM achieving a record spectral efficiency of 5.68 b/s/Hz and a first demonstration of 200Gbps and 250Gbps wavelengths and 16-QAM modulation over a trans-Atlantic submarine route using a real-time coherent DSP.

"Facebook wants to increase the pace of innovation and adoption of next-generation optical technologies,” said Dr. Stephen Grubb, global optical network architect at Facebook.

“This field trial with Nokia demonstrates that the scalable optical technology of PCS together with narrow linewidth laser sources can achieve capacities extremely close to the Shannon limit. This ensures that we are both maximising our investment in submarine cable systems, as well as continuing to drive the cost per bit of submarine transport lower."

PCS, an area of active Nokia Bell Labs research, is a novel technique that uses 'shaped' quadrature amplitude modulation (QAM) formats to flexibly adjust transmission capacity to near the physical limits of a given fibre-optic link.

Sam Bucci, head of optical networking at Nokia, added: "We are thrilled to partner with Facebook to promote our common commitment to accelerating innovation in optical transmission. By demonstrating promising areas of Nokia Bell Labs research such as PCS, as well as coherent technologies available today, we hope to chart a path forward for the industry towards higher capacities, greater reach, and more network flexibility."

The news comes after Facebook and Microsoft announced in May 2016 that they had teamed up to build a 6,600km subsea cable system the firm claims “will be the highest-capacity subsea cable to ever cross the Atlantic with speeds of 160Tbps”. The system, which has TE SubCom selected as MAREA’s supply partner, will feature eight fibre-pairs, will also be the first to connect the US to southern Europe: from Virginia Beach, Virginia, to Bilbao, Spain. The deployment of MAREA is being operated by Telxius and is on time to be ready for service by the end of 2017.