Abstract: A method of reconfiguring a multi-wavelength communication network. The transition includes determining the union of the old and new topologies. During at least the start of the transition, the network supports the union topology. New connections are connected according to the new topology, and the old topology, as its connections expire, is gradually removed. In allocating wavelengths to a new topology, two algorithms are developed which assign wavelengths which do not color clash with the wavelength assignments of the old topology.

Abstract: Techniques for physically implementing fiber ring networks which achieve full mesh connectivity, such networks including a 2-fiber WDM ring network composed of a clockwise ring and counter clockwise ring, and a 4-fiber WDM Self-Healing Ring network. The number of wavelengths required is derived for both odd and even number of nodes on the ring. To physically set-up all required connections in the network, optimal wavelength assignment algorithms are devised so that the wavelength assignment between nodes on the ring is systematic and engenders full mesh connectivity while avoiding any possible violation of the color clash constraint. An illustrative algorithm uses a simple matrix approach for calculating the interconnection arrangement.

Abstract: A wavelength-interchanging cross-connect for use as an optical switch within a wavelength-division multiplexing (WDM) communications network in which multiple optical carrier signals at different optical wavelengths are switched in an all-optical process according to their wavelength. The cross-connect of the invention further allows the optical wavelength of the signal being switched to be changed to another WDM wavelength. The cross-connect includes a series of multi-wavelength 2.times.2 spatial optical switches. One serial path is directly connected between the spatial switches. The other serial path leads through intermediate wavelength-interchanging modules that interchange the carrier wavelengths of at least one pair of signals. Preferably, the wavelength interchanging is performed by difference frequency generation relying on second-order non-linear susceptibilities and a pump signal providing parametric gain.