We provide models for evaluating the performance, cost and power consumption of different architectures suitable for a metropolitan area network (MAN). We then apply these models to compare today's SONET/SDH metro rings with different alternatives envisaged for next-generation MAN: an Ethernetcarrier grade ring, an optical hub-based architecture and an optical time-slotted WDM ring. Our results indicate that the optical architectures are likely to decrease power consumption by up to 75 %, when compared to present day MANs. Moreover, by allowing the capacity of each wavelength to be dynamically shared among all nodes, a transparent slotted WDM yields throughput performance which is practically equivalent to that of today's electronic architectures, for equal capacity.

This paper investigates the use of optical microring resonators as switching elements in large optical interconnection fabrics. We introduce a simple physical-layer model to assess scalability in crossbar-and Benes-based architectures. We also propose a new dilated switching element that improves scalability to build fabrics of several Tbps of aggregate capacity.

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We consider the problem of scheduling the transmission of packets in an input-queued switch. In order to achieve maximum throughput, scheduling algorithms usually employ the queue length as a parameter for determining the priority to serve a given queue. In this work we propose a novel scheme to optimize the performance of a preexisting scheduler. Our main idea is to assist the scheduling decision, considering "messages" rather than queue lengths. Such messages are obtained by running an iterative parallel algorithm, inspired by a rigorous Belief-Propagation approach. We demonstrate that Belief-Propagation-assisted scheduling is able to boost the performance of a given scheduler, reaching almost optimal throughput, even under critical traffic scenarios.

Interconnection networks must transport an always increasing information density and connect a rising number of processing units. Electronic technologies have been able to sustain the traffic growth rate, but are getting close to their physical limits. In this context, optical interconnection networks are becoming progressively more attractive, especially because new photonic devices can be directly integrated in CMOS technology. Indeed, interest in microring resonators as switching components is rising, but their usability in full optical interconnection architectures is still limited by their physical characteristics. Indeed, differently from classical devices used for switching, switching elements based on microring resonators exhibit asymmetric power losses depending on the output ports input signals are directed to. In this paper, we study classical interconnection architectures such as crossbar, Benes and Clos networks exploiting microring resonators as building blocks. Since classical interconnection networks lack either scalability or complexity, we propose two new architectures to improve performance of microring based interconnection networks while keeping a reasonable complexity.

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Designing switching architectures for network routers and switches needs to consider limits imposed by the electronic technology, like small bandwidth×distance factors, power density constraints, energy consumption and dissipation issues. Introducing optical technologies to implement switching functions can overcome several of the current design limits. We propose a cost-effective architecture implementing an optical switch without any need for optoelectronic conversion within the switching fabric. We further propose a distributed scheduling scheme, based on an extension of the Fasnet protocol, and we compare it to classical centralized scheduling algorithms, showing that a distributed scheduler can provide performance comparable to the ones offered by more complex centralized schedulers.