Overall subsea capacity is always going up, sometimes because of new cables but sometimes due to improvements in the technology using them. Yesterday Infinera claimed a few new such milestones leveraging its latest gear on the MAREA transatlantic cable system.
Working with an unnamed internet content provider (Microsoft and Facebook helped develop the system, could be either I guess), Infinera achieved new records for transatlantic, real-time spectral efficiency. They managed 6.21 bits per second per hertz and 26.2Tbps per fiber over one crossing of 6,644km, and 4.46 b/s/Hz and 18.6Tbps over the round trip distance. With eight fiber pairs enabled by such technology, the full MAREA cable system could theoretically support over 200Tbps.
To do that, Infinera used it's fourth generation Infinite Capacity Engine, combining 16QAM, multi-carrier common wavelocking, "near Nyquist" pulse shaping, and some very tight channel spacing. And of course it helps that they were able to use modern fiber with large effective area.