DWDM Transmission with 7.0-bit/s/Hz Spectral Efficiency using 8×65.1-Gbit/s Coherent PDM-OFDM Signals

Abstract
Spectral efficient transmission of 8x65.1-Gbit/s PDM-OFDM is reported over 240 km. Using coherent detection and 32-QAM subcarrier modulation the channel spacing is reduced to 8 GHz, allowing a net spectral efficiency of 7.0 bit/s/Hz.