Rate Adaptation and Reach Increase by Probabilistically Shaped 64-QAM: An Experimental Demonstration

• Published in: Journal of lightwave technology 2016-04, Vol.34 (7), p.1599-1609
• Main Authors: Buchali, Fred, Steiner, Fabian, Bocherer, Georg, Schmalen, Laurent, Schulte, Patrick, Idler, Wilfried
• Format: Article
• Language: English
• Subjects: Adaptive optics; Decoding; Distribution matching; Encoding; Forward error correction; optical fiber communication; probabilistic amplitude shaping; Probabilistic logic; Quadrature amplitude modulation; rate-adaptation; spatially coupled codes
• ISSN: 0733-8724; 1558-2213
• DOI: 10.1109/JLT.2015.2510034

A transmission system with adjustable data rate for single-carrier coherent optical transmission is proposed, which enables high-speed transmission close to the Shannon limit. The proposed system is based on probabilistically shaped 64-QAM modulation formats. Adjustable shaping is combined with a fixed-QAM modulation and a fixed forward-error correction code to realize a system with adjustable net data rate that can operate over a large reach range. At the transmitter, an adjustable distribution matcher performs the shaping. At the receiver, an inverse distribution matcher is used. Probabilistic shaping is implemented into a coherent optical transmission system for 64-QAM at 32 Gbaud to realize adjustable operation modes for net data rates ranging from 200 to 300 Gb/s. It is experimentally demonstrated that the optical transmission of probabilistically shaped 64-QAM signals outperforms the transmission reach of regular 16-QAM and regular 64-QAM signals by more than 40% in the transmission reach.