Detection of alien signal injection in passive optical networks

摘要

The location of a source (X) of an alien signal propagating upstream in a passive optical network (1) is identified by a method which cuts off downstream signals from an optical line terminal (2) to the branches (5) of the optical network and detects which network branch (5x) is still propagating a signal upstream despite the absence of downstream signals. A1-to-N branching device (4) comprising active optical-electrical-optical converters (41,42) implements the source-localization method by: controlling active converters of the branching device to cut off the downstream transmissions from the OLT (2), and detecting signal power on a particular network branch (5x) after the OLT transmissions have been interrupted. The branching device (4) may isolate the offending network branch (5x) from the OLT (2) using the active converter (42) connected to this network branch (5x) and may notify the OLT (2) of the offending port (Bx) or network branch (5x). The branching device (4) may monitor upstream signals from the offending network branch (5x) and re-connect the network branch (5x) if the interfering upstream signals disappear.