Waveband Optimization in ROADM-based Optical Networks

Limited reconfigurable optical add/drop multiplexers (L-ROADMs) can significantly reduce the cost of metro optical wavelength-division multiplexing (WDM) networks by limiting the range of wavelengths that can be accessed at each node. In this work, we investigate the impact of wavebanding in ROADM-based optical networks. Considering L-ROADMs and fully tunable transponders at each node, we calculate the minimum worst-case tunning range of L-ROADMs in uni- and bi-directional ring networks for static traffic, permutation and all-to-all. In L-ROADMs, tuning range determines the set of wavelengths that can be added/dropped at a reconfigurable node. A lightpath can be established between two nodes on a wavelength only if the same wavelength can be added/dropped at both nodes. There is only one single L-ROADM (the worst-case band size) per node. For permutation traffic, we show that at least one fully reconfigurable ROADM (F-ROADM) is necessary for uni-directional ring topology, and we also give an upper bound on the number of F-ROADMs needed as a function of the range of the other nodes that are L-ROADMs. For the bi-directional ring topology, we show that none of the ROADMs needs to be an F-ROADM and an upper bound of ROADM's band size is W -- floor [ W/4] where W is the number of wavelengths per fiber needed to support the traffic. For all-to-all traffic, we show that L-ROADMs can be used in all network nodes without compromising the network's performance and none of the nodes need to be an F-ROADM. For uni-directional ring network, we present a lower bound of ceil [(W + 2)/2] for the band size of the L-ROADMs. For both networks topologies, we give integer linear programming formulations that solve this assignment problem optimally and present a heuristic for L-ROADMs. For limited-add ROADMs (LA-ROADMs), we present a heuristic that minimizes the band size in the add-side of LA-ROADMs. We then consider the case where each node in the network has multiple L-ROADMs with the same band size. For both ring and mesh networks, we develop integer linear programming formulations and present heuristic algorithms to find the minimum total number of L-ROADMs required with a fixed band size bs. We also examine the performance of our design solutions under dynamic traffic. Finally, we investigate the waveband switching technique to reduce the switching costs of the network. In waveband switching, wavelengths are grouped and switched together as a waveband. We solve an optimization problem to find the minimum total number of wavebands required in a mesh network. We develop an integer linear programming formulation and present a heuristic to find the minimum number of wavebands and compare it to wavelength switching. We also examine the performance of our results under dynamic traffic.;This dissertation investigates waveband optimization in ROADM-based optical networks in order to reduce the cost without sacrificing the network performance.