Upgrading Nodes with Colorless, Directionless, and/or Contentionless ROADMs in an Optical Transport Network

Abstract

Reconfigurable optical add/drop multiplexers (ROADMs) are critical for flexible lightpath establishment and release in an optical transport network. Today, a large number of colorless (C) ROADMs have been deployed in optical networks. However, with the maturity of colorless, directionless, and/or contentionless (CD/CDC) ROADMs, carriers start to upgrade their network nodes with these because of their more flexible lightpath reconfiguration capabilities. This therefore leads to the important problem of deciding the best strategy for RODAM node upgradation. In this paper, we explore this research problem and propose various strategies for ROADM node upgradation under dynamic lightpath traffic demands. Specifically, we consider how to upgrade nodes from C ROADMs to CD ROADMs and eventually to CDC ROADMs. We also evaluate the maximum benefit obtainable by deploying these more advanced ROADMs. Our simulation studies show that the proposed strategies are efficient in significantly improving lightpath blocking performance. We also find that CD ROADMs are cost-effective to achieve performance close to that of CDC ROADMs.