Over the past five years coherent transmission technologies have delivered more than an order of magnitude improvement in the capacity-reach product for long haul DWDM transmission systems. Early coherent implementations were generally characterized by fixed grid operation and receiver-based coherent processing. More recently coherent technology has advanced and is now characterized by flexible grid operation, and a range of compensation technologies that are divided between the transmitter and the receiver. New and innovative coherent techniques promise to deliver even greater flexibility for capacity-reach product in long haul and subsea transmission systems, as well as enabling support for new, high dispersion subsea and terrestrial cable types. This presentation gives a brief overview of how these new technologies work, and the expected improvements each can deliver.
