New modulation technique allows 1Tbit/s on optical fibre network

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Nokia Bell Labs, Deutsche Telekom T-Labs and the Technical University of Munich (TUM) claim to have used a new modulation technique to transmit data at 1Tbit/s on an optical fibre network. This was close to the theoretical maximum information transfer rate of that channel and the Shannon Limit of the fibre link. The breakthrough research could extend the capability of optical networks to meet data traffic demands.

In an optical communications field trial, the researchers showed that the flexibility and performance of optical networks can be maximised when transmission rates are dynamically adapted to channel conditions and traffic demands.

The modulation approach, known as Probabilistic Constellation Shaping (PCS), uses quadrature amplitude modulation (QAM) formats to achieve higher transmission capacity over a given channel without increasing the optical network complexity.

PCS modifies the probability with which constellation points are used. Traditionally, 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, on average, are more resilient to noise and other impairments. This allows the transmission rate to be tailored to fit the transmission channel, delivering up to 30% greater reach.

“Future optical networks not only need to support orders of magnitude higher capacity, but also the ability to adapt to channel conditions and traffic demand,” said Marcus Weldon, president Nokia Bell Labs and Nokia CTO. “PCS offers great benefits to service providers and enterprises by enabling optical networks to operate closer to the Shannon Limit to support massive datacentre interconnectivity and provide the flexibility and performance required for modern networking in the digital era.”