Evaluating add/drop contention blocking in non-contentionless ROADMs

In this paper, we evaluate the capacity reduction in a network composed of directionless-colorless ROADMs, caused by the internal blocking of the ROADMs that are not contentionless. We are interested in determining the number of add/drop modules, so-called add/drop contention factor C, that eliminate this capacity reduction in practice. Under simulation, we show that a moderated contention factor (C = 2) is sufficient to roughly provide the same performance as contentionless nodes in terms of either blocking probability in the long-run or carried traffic before the first blocking event. Results were obtained within the Net2Plan tool, and source code is publicly available on Net2Plan website.