Hierarchical WDM in client-server architecture

摘要

An optical ring network comprising; a plurality of network elements including a core network element interfacing the ring network with an external core network, and at least one ring network element; wherein the core network element includes a first CWDM unit, a first DWDM unit and switching means arranged to cross connect any wavelength channel within or between wavelength bands on the ring network or between the ring network and the core network, and wherein the ring network elements each include; a second CWDM unit and a second DWDM unit, the second CWDM unit being arranged to add/drop at least a first wavelength band at said ring network element from and to the second DWDM unit and to express other wavelength bands onto the next network element.