Nokia Bell Labs, Deutsche Telekom T-Labs and the Technical University of Munich say they have achieved a 1-Tbps transmission rate over optical fiber with a new modulation technique they say extend the capability of optical networks to meet surging data traffic demands.
The trial of the modulation approach, known as Probabilistic Constellation Shaping (PCS), uses quadrature amplitude modulation (QAM) formats to achieve higher transmission capacity over a given channel to significantly improve the spectral efficiency of optical communications.
PCS modifies the probability with which constellation points – the alphabet of the transmission – 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 ideally fit the transmission channel, delivering up to 30% greater reach.
In short, PCS enables increases in optical fiber flexibility and performance that can move data traffic faster and over greater distances without increasing the optical network complexity.
The net 1-Tbps transmission rate achieved during the trial is close to the theoretical maximum information transfer rate of that channel and thus approaching the Shannon Limit of the fiber link.
“Information theory is the mathematics of digital technology, and during the Claude E. Shannon centenary year 2016 it is thrilling to see his ideas continue to transform industries and society,” said Gerhard Kramer, Professor, Technical University of Munich.“ Probabilistic constellation shaping, an idea that won a Bell Labs Prize, directly applies Shannon’s principles and lets fiber optic systems transmit data faster, further, and with unparalleled flexibility.”
Marcus Weldon, president of Nokia Bell Labs & Nokia CTO, said that 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.
“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 datacenter interconnectivity and provide the flexibility and performance required for modern networking in the digital era,” Weldon said.
The trial was carried out as part of the Safe and Secure European Routing (SASER) project.