Abstract: A node comprises a first communications interface to a customer network element, where the first communications interface is part of a group of communications interfaces to the customer network element to provide failover support. The node further includes a network interface to communicate over a trunk group to other nodes, where the trunk group includes a primary trunk and a secondary trunk. Just one of the primary and secondary trunks is active for communicating data units.

Abstract: A node comprises a first communications interface to a customer network element, where the first communications interface is part of a group of communications interfaces to the customer network element to provide failover support. The node further includes a network interface to communicate over a trunk group to other nodes, where the trunk group includes a primary trunk and a secondary trunk. Just one of the primary and secondary trunks is active for communicating data units.

Abstract: A node comprises a first communications interface to a customer network element, where the first communications interface is part of a group of communications interfaces to the customer network element to provide failover support. The node further includes a network interface to communicate over a trunk group to other nodes, where the trunk group includes a primary trunk and a secondary trunk. Just one of the primary and secondary trunks is active for communicating data units.

Abstract: A node comprises a first communications interface to a customer network element, where the first communications interface is part of a group of communications interfaces to the customer network element to provide failover support. The node further includes a network interface to communicate over a trunk group to other nodes, where the trunk group includes a primary trunk and a secondary trunk. Just one of the primary and secondary trunks is active for communicating data units.

Abstract: A node comprises a first communications interface to a customer network element, where the first communications interface is part of a group of communications interfaces to the customer network element to provide failover support. The node further includes a network interface to communicate over a trunk group to other nodes, where the trunk group includes a primary trunk and a secondary trunk. Just one of the primary and secondary trunks is active for communicating data units.

Abstract: An optical data throughput protection switch is provided which provides access to a data-carrying first optical path in a manner which protects the data from interference from equipment utilizing said access, and eliminates optical connectors along the first optical path. The protection switch includes a controlling means and a controllable switch which is optically coupled to the first optical path the termination of a second optical path. The controllable switch is controlled by the controlling means and functions to enable and disable optical coupling between the termination, of the second optical path and the first optical path. This may be effected in a manner that allows access to the first optical path when there is no data traffic thereon, and denies access thereto when data is present, resulting in data throughput on the first optical path being protected from signals of the second optical path.

Abstract: In a method and apparatus for tracking dynamic characteristics of an optical amplifier, optical signal probes are used to determine the gain and the corner frequency of the optical amplifier. A first optical probe having a predetermined modulation frequency above an expected corner frequency of the amplifier is used to estimate the gain of the optical amplifier. A second optical probe signal having a second predetermined modulation frequency at or below the expected corner frequency of the amplifier is used to estimate the corner frequency. These parameters can be used to optimize gain control of an optical amplifier.

Abstract: In a method and apparatus for tracking dynamic characteristics of an optical amplifier, optical signal probes are used to determine the gain and the corner frequency of the optical amplifier. A first optical probe having a predetermined modulation frequency above an expected corner frequency of the amplifier is used to estimate the gain of the optical amplifier. A second optical probe signal having a second predetermined modulation frequency at or below the expected corner frequency of the amplifier is used to estimate the corner frequency. These parameters can be used to optimize gain control of an optical amplifier.

Abstract: An optical data throughput protection switch is provided. The optical data throughput protection switch provides access to a data-carrying first optical path in a manner which also protects the data from interference from equipment utilizing said access, and provides for the elimination of optical connectors along the first optical path. The optical data throughput protection switch consists of a controllable switch and a controlling means, the controllable switch optically coupled to a first optical path carrying data throughput, and also optically coupled to the termination of a second optical path. The controllable switch is controlled by the controlling means and functions to enable and disable optical coupling between the termination of the second optical path and the first optical path.

Abstract: The present invention relates to an apparatus for generating a control signal for at least one periodic filter arranged to filter the optical profile of a signal, at least one of the phase and the amplitude of the filter being tunable, the apparatus comprising an optical waveguide for receiving a portion of said signal, optical filtering means connected to said waveguide for filtering the received portion, and arranged to act as a first and second periodic filter, each having substantially the same period as the filter to be controlled, the phase between the periods of the first and second filters being a non-integer of &pgr;, and optical power measuring means arranged to measure the optical power of the signal transmitted by said optical filtering means. A method is also described for determining such a control signal. Such periodic filters can be used to flatten the gain profile of an optical amplifier.

Abstract: In a WDM optical transmission system employing optical amplifiers in its transmission path, a supervisory signal channel, used for monitoring and controlling the operation of the amplifiers and spectrally separated from the data transmission, may be multiplexed with the data. A construction of amplifier is disclosed which is capable of being upgraded with an upgrade of the transmission system to include additional data handling capacity, for instance data transmission in an additional waveband and/or in the opposite direction, without interruption of the pre-upgrade data transmission path through the amplifiers. This is accomplished by the use of channel dropping and insertion filters disposed so that the amplifying data transmission path extends via the drop/insertion channel of those filters.