Advanced modulation formats, e.g. multi-dimensional modulation, probabilistic shaping, and geometric shaping, are promising candidates to realize beyond 400 Gbps serial long haul transmission. Multi-dimensional modulation encoded with a short block length extends the minimum Euclidean distance between multi-dimensional symbols, resulting in improving noise tolerance. We have recently proposed eight-dimensional (8D)-16QAM with low-complexity iterative demodulation scheme and have demonstrated 600 Gbps/wavelength 120-GBaud 8D-16QAM WDM transmission over 3,900 km. In this paper, we discuss a design method of multi-dimensional modulation formats and demodulation techniques.
|