400 Gb/s WDM DP-256-QAM transmission with 50 GHz channel separation

We demonstrate WDM transmission of seven 50 GHz-spaced 400 Gb/s (30 GBaud) DP-256-QAM channels over 52 km of SMF. Transmission relied on a frequency comb, generating kHz-linewidth, high OSNR carriers to demonstrate compatibility with metro and inter-data-center applications.