Abstract. Motivated by the increasing importance of multifiber WDM networks we study two routing and wavelength assignment problems in such networks:Fiber Cast Minimization: the number of wavelengths per fiber is given and we want to minimize the cost of fiber links that need to be reserved in order to satisfy a set of communication requests; we introduce a generalized setting where network pricing is nonuniform, that is the cost of hiring a fiber may differ from link to link. W avelength Minimization: the number of available parallel fibers on each link is given and we want to minimize the wavelengths per fiber that are needed in order to satisfy a set of communication requests. For each problern we consider two variations: undirected, which corresponds to full-duplex communication, and directed, which corresponds to one-way communication. Moreover, for rings we also study the problern in the case of pre-determined routing. We present exact or constant-ratio approximation algorithms for all the above variations in chain, ring, star and spider networks.
lntroductionAll-optical networks make it possible to transmit data at very high speed. The technology that enables transmitting more than one signal along a single optical fiber is called Wavelength Division Multiplexing (WDM); many signals can be simultaneously carried over the same physical link by light beams of different wavelengths. Recent developments make it possible to use multiple fibers on each link, allowing any signal to switch fiber at any node; however, it is preferred for each signal to remain on the same wavelength from t ransmitter to receiver, in order to avoid wavelength conversion.A multifiber network can be described by a graph G = (V, E) and a function fJ-: E ---+ lN that defines the multiplicity of fibers on each link. The set of requests R is a set of pair of nodes. A routing and path multicoloring 1 for n ( w .r. t. fJ-( e)) 1 Color collisions between paths that use the same edge are allowed , so we use the term "path multicoloring", as opposed to classical "path coloring" where paths that share an edge must receive different colors.