Scalable multihop WDM passive ring with optimal wavelength assignment and adaptive wavelength routing

Ring networks have drawn wide attention due to token ring and FDDI standards. This paper presents a scalable multihop WDM passive ring architecture for local area or metropolitan area networks. The network consists 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 called "wheel" as the optical connectivity and embedding it onto a single-loop fiber ring. Each network access node requires only a small number of fixed-tuned transceivers and an ATM switch. The network can incrementally 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 more wavelengths are required. This architecture has an excellent ability for alternative routing and optimal wavelength reuse. We present three distributed adaptive wavelength routing algorithms and an optimal wavelength assignment algorithm which minimizes the number of wavelengths used. A method yielding the lowest possible call blocking probability for an "ideal" network with a fixed number of transceivers per node is presented and used as a yardstick to evaluate the proposed networks. The numerical results show that the architecture is very efficient.