Nodal Architectures and the Optical Service Channel

The most important element in a network is the node. For WDM layered hierarchy, different configurations have been proposed, each adhering to some different set of requirements. In fact, the access, metro, and core networks have their own unique combination of nodal architectures.

A good nodal architecture is characterized by low insertion loss, low polarization-dependent and wavelength-dependent losses, high scalability (to number of wavelengths), and good switching prowess. In addition to the fore-mentioned desired characteristics, a node should also be able to configure and communicate to other nodes about lightpath establishment. The node does this through the network management system (NMS), which is typically built to provide end-to-end provisionability (ability to provision the network) in the network. The service user controls the nodal elements by using the element manage-ment system (EMS), which is like an operating tool to operate the node locally in various scenarios.