Seimetz, M.M.Seimetz2022-03-042022-03-042009https://publica.fraunhofer.de/handle/publica/22088210.1007/978-3-540-93771-5_92-s2.0-67449087432This chapter summarizes the major trends in system performance which result from migration to higher-order modulation formats. Tendencies regarding relevant system parameters such as noise performance, laser linewidth requirements, chromatic dispersion tolerances and self phase modulation tolerances are identified. The principal impact of the choice of particular transmitter configurations and receiver schemes on system performance is outlined. Furthermore, the reduction of transmission distances achievable with high-order modulation formats is briefly discussed. Finally, goals for future research in this field are pointed out.en621book article