Facebook and Nokia improve subsea fibre performance

Nokia and Facebook have joined forces for trials of new optical digital signal processing technologies over a 5,500km transatlantic subsea link.

To increase the capacity capabilities of subsea fibre, Nokia and Facebook tested Nokia Bell Labs’ probabilistic constellation shaping (PCS) technology.

The test showed an increase of almost 2.5x more capacity than the stated optical transmission capacity of the system.

Technical details

PCS is a 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.

In an experiment for an installed submarine link, PCS based on 64 QAM, combined with digital nonlinearity compensation and low-linewidth lasers, achieved a record spectral efficiency of 7.46 b/s/Hz, indicating the potential to upgrade the cable to 32Tbps per fibre.

Transmission tests based on the Nokia Photonic Service Engine 2 (PSE-2) validated the successful transmission of 8-QAM wavelengths running at 200Gbps and 16-QAM wavelengths running at 250Gbps.

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Facebook and Nokia improve subsea fibre performance