Nokia Bell Labs, Deutsche Telekom T-Labs, and the Technical University of Munich (TUM) joined forces to achieve 1-Tbps transmission capacity and what they assert is unprecedented spectral efficiency in a field trial via a new modulation technique known as probabilistic constellation shaping (PCS). The technique supports adjustable transmission rates adapted to channel conditions and traffic demands.

Traditionally in coherent transmission, all constellation points are used with the same frequency. PCS uses constellation points with high amplitude less frequently than those with lesser amplitude to transmit signals that are, on average, more resilient to noise and other impairments, say the researchers. This enables tailoring of the transmission rate to fit the transmission channel and deliver up to 30% more reach. It also significantly improves spectral efficiency, says the team.

The experiment, part of the Safe and Secure European Routing (SASER) project, achieved a net 1-Tbps transmission rate over a deployed fiber-optic network of Deutsche Telekom.

"Future optical networks not only need to support orders of magnitude higher capacity, but also the ability to dynamically adapt to channel conditions and traffic demand," says Marcus Weldon, president of Nokia Bell Labs and Nokia's chief technology officer. "Probabilistic constellation shaping offers great benefits to service providers and enterprises by enabling optical networks to operate closer to the Shannon Limit to support massive data center interconnectivity and provide the flexibility and performance required for modern networking in the digital era."

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