Ayman G. Fayoumi

Performance model of an optical switch using fiber delay lines for resolving contentions

The performance of an optical switch that handles contention resolution using a fiber delay line (FDL) is modeled and evaluated. We propose using a simple optical buffer that contains only a single FDL for contention resolution. The analytical model derived for the performance of an optical switch based on this buffer is verified using simulations. The analytical model can be utilized with both packet and burst switching schemes to characterize the performance of switches augmented with this FDL architecture.

Performance tradeoffs of shared limited range wavelength conversion schemes in optical WDM networks

Performance of all-optical switches that employee different types of limited-range wavelength converters (LRWC) are investigated. Previous work has shown that there is a remarkable improvement in blocking probability while using LRWC over full range conversion, but has not considered the coincident effect of conversion resources sharing. We consider the case where an incoming wavelength can be converted to a range of outgoing wavelengths, where d is the range of conversion. The simulation results demonstrate that the performance improvement obtained by full range wavelength conversion can almost be achieved by using a fractional ranged LRWC.

Performance Analysis of Multi-Fiber Synchronous Photonic Share-per-link Packet Switches

A performance model is presented for an optical packet switch architecture in which the wavelength converters are shared per output link and each output link consists of multiple fibers. Symmetry of the switch is exploited to derive the packet loss probability for the case where traffic is destined to different output ports with equal probability. The architecture performance is evaluated by means of an analytical model and confirmed by simulations under different switch parameter configurations. Wavelength converters are shown to improve the packet loss probability of the switch. The study shows that synchronous switches equipped with full conversion would have the least conversion utilization rate indicating that the use of a switch with less converter count, i.e., partial conversion, would offer better switch resources utilization and comparable packet loss performance

A surjective-mapping based model for optical shared-buffer cross-connect

A Surjective-Mapping based Model (SMM) is developed to evaluate the performance of a slotted optical shared-buffer cross-connect. The model is simple, accurate, and yet provides comprehensive performance characteristics of the switch. The model also overcomes the limitations of traditional Markovian based models in evaluating moderate to large switches, associated with the explosion of number of states. The model is verified using simulation results for different switch sizes and different numbers of delay lines. The model enables dimensioning the switch architecture to meet the target performance. Performance of optical shared-buffer cross-connect is analyzed in detail, in terms of blocking probability, delay distribution, and delay line utilization.

Performance of multihop networks using optical buffering and deflection routing

Multihop networks such as the Manhattan Street Network (MSN) are strong contenders for implementing high-speed networks, ranging from back-plane networks for cluster computing to metropolitan-area networks. Optical buffering may be used to augment optical multihop networks, and to reduce or even eliminate the need for optical-electrical conversions. This paper evaluates the performance enhancements obtainable by augmenting traditional MSN with optical buffering, thus combining optical buffering and deflection routing for contention resolution. The network is based on a novel 6/spl times/6 optical switching node. A great improvement in performance over the traditional MSN is obtained for a large range of network parameters.

Effects of Optical Buffering on the Performance of Manhattan Street Networks

Multihop networks are strong candidates for the implementation of high-speed networks, ranging from back-plane networks for cluster computing to metropolitan-area networks. Besides using deflection routing for contention resolution, optical buffering may be used to enhance the performance of optical multihop networks and to reduce or even eliminate the need for optical-electrical conversions. The enhancements obtained by augmenting traditional MSN (Manhattan Street Networks) with optical buffering are evaluated. The MSN considered here is based on a novel 6 × 6 optical switching node with up to two fiber delay loops. Impact of the parameters associated with optical buttering, such as the number of delay loops and the loop length, are discussed in detail.

Performance tradeoffs of optical WDM switches using different shared limited-range wavelength conversion mechanisms

The effects of different wavelength conversion ranging configurations on the performance of Wavelength Division Multiplexing (WDM) optical switches are investigated. Any-to-Any, Any-to-Range, Range-to-Any, and Range-to-Range conversion ranging configurations are considered. These mechanisms provide important design alternatives for optical switches due to technological limitations in the implementation of full range wavelength conversion in an all-optical wavelength converter device. Limited-range wavelength converter (LRWC) is a more economical and practical solution for WDM based optical networks. Differences among the input and output side ranging mechanisms and their effects on conversion resource sharing, and consequently on performance, are investigated. Any- to-Range ranging configuration is the most efficient mechanism and it operates comparably to Any-to-Any, reducing the need for complex control algorithms. The results help determine the most efficient ranging configuration for all-optical crossconnect.

All-optical cross-connect using feed-forward optical buffers with and without QoS: an analysis

An analytical model is derived to evaluate the performance of an optical switch using a feed-forward fiber delay line (FDL) per output for contention resolution. Two different forwarding algorithms for the switch are presented and evaluated: a simple forwarding algorithm (SFA) that is easier to implement, and an enhanced algorithm that provides better performance in terms of both packet loss probability and packet delay. The analytical model can be utilized with both packet and burst switching schemes to characterize the performance of the proposed architecture. Results show that the proposed architecture reduces the packet loss probability compared to that without FDLs. Finally, the same architecture is shown to be capable of supporting Quality of Service (QOS).

Performance Evaluation of an All-Optical ShuffleNet using Optical Buffering and Deflection Routing

All-optical multihop networks, where the data portion of a packet is maintained in an optically encoded format from the source to the destination, can be achieved by augmenting optical switching nodes with optical buffering. Topologically, the ShuffleNet network is a strong contender for implementing such networks ranging from cluster networks to metropolitan area networks. The performance of a regular multihop network whose nodes are augmented with optical buffering and use deflection routing is evaluated. Using the ShuffleNet network as an example, we show that performance, in terms of throughput, average delay, and loss probability, can be improved as multiple fiber delay loops are added for a large range of network parameters. We then compare the performance of ShuffleNet with the Manhattan Street networks with similar features.

Comparison of optical buffering and store-and-forward mechanisms in optical networks

An all-optical Manhattan Street Network (MSN), in which the data portion of a packet is maintained in an optically encoded format from the source to the destination, can be achieved by augmenting MSN with optical buffering. Augmenting MSN with optical buffering improves its performance significantly and reduce its complexity by reducing or even eliminating the need for optical-electrical conversions. The performance of an MSN with optical buffering is compared with that of an MSN in which only store-and-forward routing mechanism is used. The network is based on a novel 6x6 optical switching node.