Wavelength-routed Optical Network Topology

Recently the volume of the Internet traffic has been increasing rapidly as the growth of the population of Internet users,which is requiring more and more network bandwidth. To accommodate the Internet traffic,the capacity of backbone networks has been enhanced by WDM(Wavelength Division Multiplexing).WDM-based wavelength-routed optical networks have been widely considered a promising network infrastructure for next-generation optical networks.The nodes in wavelength-routed optical network are connected with dedicated virtual circuits called lightpaths.By configuring lightpaths,a logical topology is constructed over a wavelength-routed network where lightpath is setup by assigning a dedicated wavelength to it on each link in its path.For example,to define a lightpath from node x to node y,the node x must broadcast to the passive optical coupler at a wavelengthλ_x,yand the node y must be capable of receiving this optical signal by tuning its receiver to the same wavelengthλ_x,y.So lightpath is the precondition of lightwave communication in optical networks.The principles of setuping the lightpaths are:in switching center,after receiving an establishment request, then search whether there is a free channel in the light channel which the end-nodes use,if there is one,then establish this connection,otherwise discard this application.Wavelength-routed optical network may be categorized as single-hop or multi-hop networks. A single-hop network allows communication between any source-destination pair using a single lightpath from the source to the destination.In a multi-hop network,to communicate from a source to a destination,it is necessary to use a composite lightpath consisting of a number of lightpaths.And in a multi-hop network,the information can reach the destination through the different paths.How to enable the information which every node sends out to find a shortest path to reach the destination so that the transmission delay of the entire network is the minimum.This question has been one of hot topics of wavelength-routed optical network research.Many investigations indicate that the performance of a network is largely decided by its topology.Since different topologies may result in the difference in performance,the most important problem is certainly the topology as studying the the performance of network.Optimizing the topology of network will reduce the transmission delay and congcstion of network.The logical topology is usually represented by a directed graph G=(V,E)(where V is the set of nodes and E is the set of edges)with each node of G representing a node of the physical topology and each edge(denoted by uâ†'v)representing a direct all-optical lightpath from node u to node v.In the graph representation of the logical topology of a multihop network,for communication from u to v,we can represent the composite lightpath L consisting of the lightpaths L₀,L₁,...,L_k-1by the graph-theoretic path uâ†'x₁â†'x₂â†'…â†'x_k-1â†'v.The graph is desired to have small nodal degree,simple routing scheme and small diameter for low cost and high-speed communication.In the thesis,we mainly study the structures and the properties of wavelength-routed optical network,and obtain some interesting results.Five chapters are included in the thesis.We illuminate the research background,put forward of the problems and give the structure of the thesis in Chapter 1.In Chapter 2,we introduce the structures,properties and the corresponding design issues for wavelength-routed optical networks.In Chapter 3,we mainly study some typical topologies of multihop wavelength-routed optical networks,and analyze and compare their performances,respectively.In Chapter 4,we design flexible and scalable topologies of wavelength-routed optical networks,and prove the corresponding properties. The following problems for future research are given in Chapter 5.