Abstract: The virtually unused switching fabric of an OC-192 SONET transport node is used to greater effect when used as a switching node. Several of the nodes are used in the central office (CO) of a communication network. Each node terminates an optical network link and each node hosts a number of transport cards that also terminate different optical network links. The nodes provide space-switching between the cards. Additionally an intra-CO optical link is provided that interconnects the nodes to allow traffic flow between any of the optical network links in the CO that are terminated by transport cards or the nodes.

Abstract: The virtually unused switching fabric of an OC-192 SONET transport node is used to greater effect when used as a switching node. Several of the nodes are used in the central office (CO) of a communication network. Each node terminates an optical network link and each node hosts a number of transport cards that also terminate different optical network links. The nodes provide space-switching between the cards. Additionally an intra-CO optical link is provided that interconnects the nodes to allow traffic flow between any of the optical network links in the CO that are terminated by transport cards or the nodes.

Abstract: A new architectural arrangement for network elements deployed in a central office (CO) is disclosed. The architectural arrangement involves dividing the network elements into an optical layer comprised of elements that have optical signal interfaces and switch optical signals, an opto-electrical layer comprised of elements that have optical signal interfaces and switch electrical signals, and an electrical layer comprised of elements that have electrical signal interfaces and switch electrical signals. The opto-electrical layer connects the optical and the electrical layer, and also connects lower-rate optical links into the CO. This layered architectural arrangement allows for more efficient use to be made of the small number of high-rate ports supported in the optical layer, and for the off loading of switching responsibility from both the optical and the electrical layers. This, in turn, improves the overall performance and capacity of the CO.

Abstract: A MQW semiconductor Mach Zehnder phase modulator is formed by two Y-junctions (12, 32), each having a single waveguide (14) optically coupled with two branch waveguides (18, 20). The branch waveguides of the two Y-juntions are optically coupled in Mach-Zehnder configuration that, under zero bias conditions, has one interferometric arm longer than the other to provide a .pi. phase shift. The additional length is preferably accommodated in the branches of the Y-junctions. The phase shift, in combination with voltage dependent absorption properties and non-linear phase variations of the MQW guided regions in the Mach-Zehnder modulator results in a negative chirp and high extinction ratio for an equal, push-pull device configuration.