Elastic optical networks can increase spectral efficiency by assigning a variable amount of spectral resources to satisfy a traffic request, instead of the fixed amount of spectrum as allocated by current fixed grid optical networks. Waveband networks reduce the number of optical switch ports by aggregating lightpaths into a waveband, and switching them with a single waveband port. We formulate the waveband selection, spectrum allocation, and waveband assignment problem in an elastic optical waveband network that supports a fixed number of waveband sizes. We propose heuristics to select waveband sizes and study the effect of the number of waveband sizes on the number of optical switch ports. We also address the spectrum allocation and the waveband assignment problem in elastic waveband networks with no restrictions on the number of waveband sizes. We propose an auxiliary graph based heuristic and study the trade-offs between spectral usage and the number of optical switch ports. Additionally, we propose traffic ordering strategies and study their efficacy in reducing the number of optical ports and efficiently utilize the optical spectrum in a waveband network.

We formulate the regenerator site selection problem as an integer linear program (ILP) and propose heuristics to solve the design problem in the context of waveband optical networks. We study the effect of the number of regenerator sites on the number of optical ports in waveband networks that support mixed line rates. Results demonstrate that increasing the number of regenerator sites reduces the electronic cost, however the optical switch port cost decreases initially and then remains the same with an increase in the number of regenerator sites.

Waveband networks allow multiple lightpaths to be aggregated and routed as wavebands, resulting in fewer switch ports. In an impairment-aware waveband network, a lightpath needs to be electronically regenerated before its signal to noise ratio reaches an unacceptable level. However, when a lightpath in a waveband needs to be regenerated the entire waveband needs to be demultiplexed into wavelengths resulting in additional wavelength ports at a node. Regenerator placement in a waveband network should be done so as to facilitate banding of lightpaths and to reduce the total cost of switch ports in the network. We formulate the regenerator placement problem in an impairment constrained waveband network as an integer linear program (ILP). We compare the performance of the heuristics with an ILP for a small size network. Results demonstrate that the proposed band-aware reachability graph heuristic yields solution that are very close to the ILP. We study the performance of the heuristics on larger networks and study their effectiveness in reducing the combined cost of optical switch ports and electronic regenerators.

In this work, we consider the problem of maximizing the reliability of connections in mesh networks against failure scenarios in which multiple links may fail simultaneously. We consider the single-path connection problem as well as multiple-path (protected) connection problems. The problems are formulated as minimum-color path problems, where each link is associated with one or more colors, and each color corresponds to a given failure event Thus, when a certain color fails, all links which include that color will fail. In a single-path problem, by minimizing the number of colors on the path, the failure probability of the path can be minimized if all colors have the same probability of causing failures. In the case of two paths, where one path is a protection path, if all colors have the same probability of causing failures, the problem becomes that of finding two link-disjoint paths which either have a minimum total number of colors, or which have a minimum number of overlapping colors. By minimizing the total number of colors, the probability that a failure will occur on either of the paths is minimized. On the other hand, by minimizing the number of overlapping colors, the probability that a single failure event will cause both paths to fail simultaneously is minimized. The problems are proved to be NP-complete, and ILP formulations are developed. Heuristic algorithms are proposed for larger instances of the problems, and the heuristics are evaluated through simulation.

As the number wavelengths in WDM systems continue to increase, the switching fabric of optical cross connects (OXCs.) becomes increasingly complex. This complexity can be reduced by introducing multi-granular OXCs (MG-OXC) into the network. An MG-OXCs is capable of switching an entire group of wavelengths through a single switch port, thereby reducing the number of switching ports and reducing the complexity of the switch fabric. In this paper, we consider the problem of establishing active and backup paths for connections in networks with MG-OXCs. The problem of establishing protected connections for a given traffic demand in MG networks differs from the protection problem in standard wavelength-routed networks in that the primary objective in MG networks is to minimize the number of switch ports in the network. The mode of protection (dedicated or shared) affects the ability to aggregate and route traffic together. We propose a graph-based heuristic that attempts to solve the problem of routing and waveband assignment in an integrated manner. The heuristic reduces the total number of ports in the MG network. We also study the effect of shared protection on the port count.