Cisco Technology, Inc.

Andrea Marchio

Lorenzo Ghioni

Mauro Rudi Casanova

Mauro Macchi

Gianpaolo Barozzi

At a WDM add/drop node of an optical fiber, an add/drop multiplexer system with opto-electric components in the through channel path has an optical switch connected in parallel with an add/drop multiplexer. Upon a power loss to the add/drop multiplexer, the optical switch bypasses the add/drop multiplexer so that WDM channel signals pass through the WDM add/drop node without interference from the unpowered add/drop multiplexer. Loss of through channels at the node is prevented. Upon a return of power, the optical switch reroutes the WDM signals on the optical fiber to the add/drop multiplexer but after the add/drop multiplexer is fully operational.

Through channel loss prevention at a WDM node

Systems and methods for verifying performance at an intermediate point in an optical link are provided by virtue of one embodiment of the present invention. One application is locating a fault along a long optical link while minimizing the need for trained personnel to inspect and monitor the link at numerous widely separated locations. At an intermediate point in the link, a portion of the optical signal present is tapped off and demodulated. By use of error correction decoding techniques on the demodulated data, the performance of the link up until that intermediate point may be verified.

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Limido Comasco, Italy

Andrea Marchio