Generation and 1,200-km transmission of 448-Gb/s ETDM 56-Gbaud PDM 16-QAM using a single I/Q modulator

We generate 56-Gbaud PDM 16-QAM using electronic time-division multiplexing (ETDM) and a four-level-driven I/Q modulator. The 448-Gb/s line-rate signal is transmitted over 1,200 km of ultra-large-area fiber and coherently received by two 32.5-GHz oscilloscopes with >5.5 effective bits.