Using RZ DPSK-Based Transponders for Upgrades on Existing Long-Haul Submarine WDM Systems

The RZ-DPSK transmission format allows higher capacity and greater flexibility in system configurations when upgrading existing WDM systems. We report on using RZ-DPSK for upgrades of systems originally designed for RZ-OOK transponders. In this paper, we discuss the use of RZ-DPSK transponders on an installed trans-Pacific link and on the Sam-1 Cable System where the original transmission lengths were significantly increased. On the original Sam-1 Cable System, each digital line segment was less than 5000 km long. At the owners request these shorter sections were concatenated to make a 10,757-km commercial WDM 10 Gb/s fiber optic link, the longest in the world. Ten Gb/s transponders were successfully deployed onto the concatenated segments, and DPSK transponders will allow 480 Gb/s capacity.