Transmission of 16.4-bit/s Capacity Over 2550 km Using PDM QPSK Modulation Format and Coherent Receiver

A record capacity distance product of 41.8 Petabit/s $\cdot$km is demonstrated. A total of 164 channels are modulated at 100 Gbit/s with PDM-QPSK format, packed with 2 bit/s/Hz information spectral density and recovered by off-line processing in a coherent receiver after 2550 km distance.