SCALABLE MULTIHOP WDM PASSIVE RING WITH OPTIMAL WAVELENGTH ASSIGNMENTAND ADAPTIVE WAVELENGTH ROUTING

Ring networks have drawn wide attention due to token ring and FDDI sta ndards. This paper presents a scalable multihop WDM passive ring archi tecture for local area or metropolitan area networks, The network cons ists of optical interfaces, which are connected into a ring by fibers. Each, optical interface is completely passive and unpowered, We apply the ''multihop'' principle by introducing a regular multiloop ring ca lled ''wheel'' as the optical connectivity and embedding it onto a sin gle-loop fiber ring, Each network access node requires only a small nu mber of fixed-tuned transceivers and an ATM switch, The network can in crementally scale up from a smaller ring to a larger ring by deploying more access nodes and optical interfaces, When scaling up the network , not only the number of wavelengths required is small but also no mor e wavelengths are required. This architecture has an excellent ability for alternative routing and optimal wavelength reuse, We present thre e distributed adaptive wavelength routing algorithms and an optimal wa velength assignment algorithm which minimizes the number of wavelength s used. A method yielding the lowest possible call blocking probabilit y for an ''ideal'' network with a fixed number of transceivers per nod e is presented and used as a yardstick to evaluate the proposed networ ks. The numerical results show that the architecture is very efficient .