Enabling technologies for ultra-long haul transmission systems

Ultra-long haul optical transmission systems are very complex, and require tremendous amount system level optimization. The process of integrating different technologies is strongly limited by system level trade-offs. Performance is not the only figure of merit, to some extend especially to ULH systems, the robustness and tolerance are more important. In this work, we will briefly summarize the key enabling technologies, and then focus on system level integration. Finally, we will discuss the future trend for ULH systems.