Solutions for 80 km DWDM Systems

Currently discussed solutions for 80 km DWDM transmission targeting inter-data center connections at 100G and 400G line rates are reviewed. PDM-64QAM, PAM4, and discrete multi-tone transmission (DMT) are investigated, while the focus lies on directly detected solutions. For DMT, the vestigial sideband approach significantly increases the tolerance toward chromatic dispersion and bandwidth limitation and gives way to a flexible DWDM 400G transceiver using four to eight wavelengths.