Abstract: A network is maintained functional in the presence of a wide range of faults, including physical fiber cuts, transmission impairments creating signal quality degradation, and failure of equipment modules, for example, transceivers, using a common control and backup channel, either alone or in combination with fiber loopback protection or wavelength loopback protection, or fiber loopback protection or wavelength loopback protection alone. Systems constructed according to the invention require only a single transceiver per wavelength at each node that accesses that wavelength. The invention is equally applicable to type 1 nodes, which drop and add a single, predetermined wavelength, and to type 2 nodes which have the capability to drop and add any subset of the wavelengths employed in the network.

Abstract: A distributed, scalable and modular asynchronous transfer mode (ATM) switching fabric is disclosed. The switching fabric includes port interface modules for connecting physical devices to the switch fabric. The switch fabric is arranged as rows of input buses running horizontally and columns of output buses running vertically. A junction module is located at each intersection of input and output buses. A switch can be constructed having any integer number M input and output buses, each input and output bus having an associated port interface module. The switching fabric for the specific case of M=2 is presented. Junction modules buffer and store cells received from the input buses and subsequently output cells onto the output buses. A junction module only accepts cells destined for one of the two output buses connected to itself. One output module is connected to each junction module situated with the same fabric column. Output modules instruct the junction modules when to store and output a cell.