On the benefit of tunability in reducing electronic port counts in WDM/TDM networks

We study the benefits of using tunable transceivers for reducing the required number of electronic ports in WDM/TDM networks. We show that such transceivers can be used to efficiently "groom" sub-wavelength traffic in the optical domain and so can significantly reduce the number of electronic ports compared to the fixed tuned case. We provide a new formulation for this "tunable grooming" problem. We show that in general this problem is NP-complete, but we are able to efficiently solve it for many cases of interest. When the number of wavelengths in the network is not limited, we show that each node only needs the minimum number of transceivers (i.e., no more transceivers than the amount of traffic that it generates). This holds regardless of the network topology or traffic pattern. When the number of wavelengths is limited, we show an analogous result for both uniform and hub traffic in a ring. We also develop a heuristic algorithm for general traffic that uses nearly the minimum number of transceivers. In most cases, tunable transceivers are shown to reduce the number of ports per node by as much as 60%.