50 Gbps PAM-4 Over Up to 80-km Transmission With C-Band DML Enabled by Post-Equalizer

In this letter, transmission of directly-modulated PAM-4 in C-band is experimentally demonstrated. Instead of introducing any optical devices for dispersion management, we employ receiver-side equalization consisting of Volterra-based FFE and Volterra-based DFE, to mitigate the signal distortions induced by the frequency chirp effect and chromatic dispersion. Results indicate that, PAM-4 transmissions of 56 Gbps over 60km and 60 Gbps over 80-km are achieved respectively under the HD-FEC limit (3.8 × 10-3) and SD-FEC limit (2.2 × 10-2).