Improving the Cost Effectiveness of WDM Optical Networks

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This proposal is a joint proposal submitted by investigators at the George Washington University and the College of William and Mary. In spite of lower error rates and far higher capacities, WDM (Wavelength Division Multiplexing) optical networks have yet to compete with their electronic counterparts in the marketplace. The main reason is the prohibitive cost of the hardware, which puts optical networks out of reach for all but a few users.The research proposed here takes aim at some of these prohibitive costs and is intended to help network designers answer some questions related to dimensioning and component-sizing that can help reduce hardware costs.The proposed research takes as a starting point an all-optical circuit-switched multifiber avelength-routing ring, a tested technology, and asks the question ``Can high performance be obtained with less hardware?'' While many aspects of a network (ranging from manufacturability to higher-level software design) make up the overall cost, this project focuses on reducing costs by limiting the complexity (crosspoints) of optical switches and from more effectively using available bandwidth by time-slotting.Three types of resource allocation problems that arise from these cost considerations will be investigated and algorithms that perform resource allocation will be designed and evaluated.The first type of problem involves limiting the flexibility of fiber-to-fiber switches in an effort to reduce the cost of manufacturing switches. Preliminary results indicate that near-optimal throughput can be obtained even with significant reduction in the connectivity of the switch. Some research questions that will be addressed in this case are: how does performance vary quantitatively with limitations in switching to fibers? does wavelength allocation differ fundamentally with these restrictions?The second type of problem involves constructing larger networks from smaller rings. Research questions for this problem include: how should all-optical multiple rings be connected in a cost-effective manner, especially by using fiber-switching limitations? how should wavelengths be partitioned (if at all) for inter-ring and intra-ring sessions?The third type of problem involves efficiently scheduling multi-rate sessions in an optical network with slots (time-division multiplexing). The practical feasibility of this technology has already been demonstrated. The focus here is on resource allocation problems that, by more effectively using bandwidth with fiber-switching limitations, reduce overall network cost.Finally, an integrative approach will be taken to study network performance when all three types of design features are present. The research results are intended to be applicable in the near future, and therefore the initial approach will use a combination of simulation and modeling, whereas later the PIs will aim for a deeper theoretical understanding of the problem.