Design issues of 40-Gbit/s WDM systems for metro and core network application

Deployment of 40-Gbit/s technology in metro and core networks is still attractive, to bring down costs and to increase transmission capacity. This paper summarises design issues of 40-Gbit/s WDM systems for their application in wavelength division multiplexed metro and core networks. Parameter tolerances and transmission distances for different modulation formats are numerically and experimentally investigated. Based on Deutsche Telekom's fibre infrastructure, upgrade studies show that polarisation mode dispersion will be the main obstacle when installing 40-Gbit/s technology in deployed fibre infrastructure.