Single-Carrier 400G 64QAM and 128QAM DWDM Field Trial Transmission Over Metro Legacy Links

We report on the results of a field trial carried out on a Telecom Italia metro link, targeting short data center interconnect applications. The test-bed presented realistic transmission conditions, such as an average ~0.3-dB/km attenuation and usage of legacy erbium-doped fiber amplifier (EDFA) only. We transmitted a net bit rate of 400 Gb/s on a single carrier with 64 quadrature amplitude modulation (QAM) and 128QAM over 156 km. Error-free transmission over 80 km for single carrier dense wavelength-division multiplexing (DWDM) $30\times 400\text{G}$ 64QAM and $30\times 400\text{G}$ 128QAM (one half of the $C$ -band) is reported. The net spectral efficiency, for both schemes, is 7.11 b/s/Hz.