'University of Pretoria - Department of Philosophy'
Abstract
The objective of this dissertation is to enhance the functionality of an existing simulation package that is used to simulate fiber optic networks. These enhancements include the capability to simulate protection mechanisms following link failure, which is a necessity in real-world optical networks to ensure the continued flow of information following a failure in a part of the network. The capability for network traffic to choose from additional paths is also an addition to the software. The enhanced, as well as the original simulation software, are open source: this allows anyone to freely modify and improve the source code to suit his or her requirements. This dissertation will focus on mesh-based optical network topologies, which are commonly found in regional optical backbone networks, but which are also increasingly found in metropolitan areas. The regional networks all make use of wavelength division multiplexing (WDM), which consists of putting multiple different wavelengths of light on the same physical fiber. A single fiber breakage will therefore disrupt multiple fiber-optic connections. A fiber-optic network designer has to satisfy various conflicting requirements when designing a network: it must satisfy current and predicted future traffic requirements, it must be immune to equipment failure, but it must also be as inexpensive as possible. The network designer therefore has to evaluate different topologies and scenarios, and a good network simulator will provide invaluable assistance in finding an optimal solution. Protection and restoration need to be looked at in conjunction with routing and wavelength assignment (RWA), to ensure that resources in a network are used at maximum efficiency. Connection restoration time will also be looked at: this should be minimised to ensure minimal network downtime and ensuing loss of revenue. The chosen alternate connection path should also be as short as possible to minimise use of resources and maximise the carrying capacity of the network. Blocking probability (the inability to establish a connection due to a congested network) is a crucial factor and is also investigated. The topologies investigated in this dissertation consist of various mesh based real-world regional WDM fiber-optic networks. The impact of various link failures, the addition of additional alternate paths, as well as the effect of a protection mechanism on these topologies are also investigated. The proposed goals were all successfully achieved. The capability of simulating single as well as multiple link failures was introduced to the simulation package. The blocking probability of various network topologies was compared to each other in the presence of link failures. Success was also achieved in the introduction of a third alternate path to the simulation package.Dissertation (MEng(Electronic))--University of Pretoria, 2005.Electrical, Electronic and Computer Engineeringunrestricte
