In a post-deadline paper delivered at ECOC 2016 in Dusseldorf, Germany, Alcatel-Lucent Submarine Networks (ASN) and Nokia Bell Labs reported they have demonstrated 65-Tbps over a 6,600-km single-mode fiber using probabilistic constellation shaping (PCS) and polarization division multiplexed (PDM) 64QAM modulation. The lab demonstration took place in a setting designed to mimic an undersea cable network, including use of submarine-grade dual-band EDFAs.
Nokia Bell Labs, Deutsche Telekom, and the Technical University of Munich announced just before the event the development of PCS as part of the Safe and Secure European Routing (SASER) project (see "Probabilistic constellation shaping yields terabit transmission"). The technique is based on non-uniform transmission of constellation symbols, in which the occurrence of high-power symbols is reduced. The resulting transmission is more resistant to noise and other impairments and can be adapted to meet changing conditions, the partners assert.
The lab transmission used both the C and L bands. Application of PCS to submarine networks could significantly boost capacity and reach, the researchers believe.
"The future digital existence where everyone, everything and every system and process is connected will require a massive increase in network capacity and the ability to dynamically optimize this capacity," said Marcus Weldon, president of Nokia Bell Labs and Nokia's CTO. "Probabilistic constellation shaping extends the limits of current optical transmission by utilizing novel modulation techniques to dramatically improve the performance and capacity needed for the new digital era that will be enabled by the Future X Network."
In addition to the demonstration with ASN, Nokia Bell researchers delivered a second post-deadline presentation that described the use of parallel probabilistic shaping to transmit PDM-256QAM signals at reaches of 500 km to 4000 km leveraging Raman amplification.
For related articles, visit the Optical Technologies Topic Center.
For more information on high-speed transmission systems and suppliers, visit the Lightwave Buyer's Guide.