Mixed Bitrate and Modulation Format Upgrades of Non-Slope Matched Submarine Links

New channels at higher bitrates using RZ-DPSK modulation are added to N×10.7-Gbit/s-ASK signals operating over transoceanic distances. Experiments and simulations are used to analyse performance and limitations, with 20-Gbit/s-RZ-DPSK being a strong candidate for upgrades.