Modeling, performance analysis, and survivability evaluation of multi-fiber WDM optical networks

Abstract

Performance goals of future high capacity optical networks may be achieved using a combination of features such as additional wavelengths, parallel fibers, converters and complex switch architectures. The trade-offs involving the use of multi-fiber multi-hop networks such as the number of fibers, number of wavelengths, conversion options, and different switch configurations are examined, and their impact on end-to-end blocking and throughput performance is evaluated. Models relating network parameters to end-to-end performance of circuit-switched all-optical networks are developed. The performance gain due to the use of multiple fibers with or without conversion is shown to be superior to the single fiber case, when the total number of wavelengths is the same, for traffic that traverses multiple hops between source and destination nodes. 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 performance is evaluated by means of an analytical model and confirmed by simulations under different switch parameter configurations. The improvement of the packet loss probability of the switch with the number of wavelength converters is characterized. The performance of the switch is also evaluated when multiple fibers are utilized at the output of the switch. The improvement of performance due to a single wavelength conversion device in optical packet switch (OPS) as well as one extra fiber with respect to the total number of wavelengths is investigated. In this research, we show that the performance of the optical packet switch could be enhanced with less cost overhead by utilizing the converter and multi-fiber link tradeoffs. Moreover, the enhancements in performance of the switch under different packet contention resolution techniques (wavelength conversion, multiple fibers) are compared. Further, the optical packet switch performance limits are identified. The results show that synchronous switches equipped with full conversion would have the least conversion utilization rate, indicating that the use of a switch with fewer converters, i.e., partial conversion, would offer better switch resources utilization and comparable packet loss performance. The number of converters that are required to achieve the best performance possible decreases when multiple fibers are utilized. Both availability and performance degradation of a system in the presence of failure are integral components of network survivability evaluation. Therefore, a composite model is presented for survivability of multi-fiber WDM networks that includes system availability analysis to discover the cost due to system downtime, and system failure impact analysis to discover the transient performance degradation when failure occurs. The results show that network design can exploit availability of multiple fibers to enhance both performance and survivability.