Transmission of 448-Gb/s dual-carrier POLMUX-16QAM over 1230 km with 5 flexi-grid ROADM passes

We show the compatibility of 448-Gb/s dual-carrier POLMUX-16QAM modulation with a 87.5-GHz flexi-grid channel spacing in the presence of cascaded optical filtering, enabling transmission over 1230 km and 5 ROADM passes with 4.8-b/s/Hz spectral efficiency.