Performance of Optical Networks With Limited Reconfigurability

We investigate the blocking performance of all-optical reconfigurable networks with constraints on reconfiguration brought by reconfigurable optical add/drop multiplexers (ROADMs) and tunable transponders. Considering a fully reconfigurable ROADM and limited tunable transponders at each ROADM port, we develop an analytical model to calculate call blocking probability in a network of arbitrary topology for two different models for transponder sharing within a node: share-per-link (SPL) and share-per-node (SPN). In such a configuration, limited tunable transponders determine the set of wavelengths that can be added/dropped at a reconfigurable node. A lightpath can only be established if a transponder on both ends can tune to the same available wavelength along the route. We call this wavelength termination constraint. The number of transponders (as many as ports) and the waveband size (the range of wavelengths over which a transponder is tunable) are the key parameters of the model, assuming that wavebands are randomly assigned to transponders. We also present a heuristic algorithm for assigning wavebands to transponders at each node and modify the analytical model to approximate the performance of the algorithm. We present simulation results to validate our model and also show results for share-per-link and share-per-node models with various sets of parameters. We show that limited tunable transponders give the same performance with widely tunable transponders in terms of blocking. We also show that transponder waveband assignment to limited tunable transponders is an important factor determining the blocking.