Abstract: The architecture for a photonic transport network provides for separation of passthru channels form the drop channels at the input of a switching node. A wavelength switching sub-system then switches the passthru channels, without OEO conversion. The drop channels are directed to broadband receiver of choice using a broadcast and select drop tree. The add channels are inserted at the output side of the node, using tunable transponders. In addition, a passthru channel may be OEO converted if signal conditioning and/or wavelength conversion are necessary. The transponders, regenerators and transceivers are not wavelength specific, allowing flexible and scaleable network configurations. This structure provides for fast provisioning of new services and ‘class of service’ network recovery in case of faults.

Abstract: A unidirectional or bidirectional node for use in an optical communications network, a network consisting of such nodes. The node comprises one or more optical couplers as well as either or both of drop circuitry connected to an output port and add circuitry connected to an input port. This allows for changes to the wavelength plan without interruption of the ring traffic. If add circuitry is used, the wavelengths in the filtered add signal should be distinct from those of the incoming signal on the main optical path which is merged with the add signal. When separate fibers are used for transmitting and receiving data between a hub and nodes in a ring, the through loss of the couplers is reduced for upstream couplers, which increases the available loss to be assigned to the fiber.

Abstract: A unidirectional or bidirectional node for use in an optical communications network, a network consisting of such nodes. The node comprises one or more optical couplers as well as either or both of drop circuitry connected to an output port and add circuitry connected to an input port. This allows for changes to the wavelength plan without interruption of the ring traffic. If add circuitry is used, the wavelengths in the filtered add signal should be distinct from those of the incoming signal on the main optical path which is merged with the add signal. When separate fibers are used for transmitting and receiving data between a hub and nodes in a ring, the through loss of the couplers is reduced for upstream couplers, which increases the available loss to be assigned to the fiber.

Abstract: A unidirectional or bidirectional node for use in an optical communications network, a network consisting of such nodes and a method of maintaining a target loss around a ring. The node comprises one or more optical couplers as well as either or both of drop circuitry connected to an output port and add circuitry connected to an input port. This allows for changes to the wavelength plan without interruption of the ring traffic. If add circuitry is used, the wavelengths in the filtered add signal should be distinct from those of the incoming signal on the main optical path which is merged with the add signal. When separate fibers are used for transmitting and receiving data between a hub and nodes in a ring, the through loss of the couplers is reduced for upstream couplers, which increases the available loss to be assigned to the fiber. The method of maintaining a target loss around a ring relies on the known through loss of the coupler at each node to set the gain of an amplifier connected to the node.