Abstract: The matched nodes provide protection for a failure in the connection between two bidirectional line switched rings. They use a secondary path in case of a primary path failure. The secondary path is set aside in either the working or protection bandwidth of the rings, thus wasting resources. The invention uses a dedicated secondary path between the primary and secondary nodes. With the invention, no ring protection mechanisms are compromised and the ring bandwidth is not wasted. Middle nodes also realize full add/drop capabilities.

Abstract: A line condition control (LCC) algorithm is disclosed that is implemented within a switching card that chooses, for information transmission, between working and protection fiber optic channels. The disclosed LCC algorithm ensures that a channel with an oscillating signal failure condition will be utilized instead of a channel with a solid signal failure condition. The LCC algorithm, input with an input line condition (ILC) corresponding to one of the fiber optic channels, outputs a corresponding output line condition (OLC) that is input to a decision algorithm within the switching card. The OLC is set to a signal degrade condition if either a protection oscillation control (POC) mechanism is activated or if a specified number of signal failure condition clearances are detected within a set time period which, in turn, activates the POC mechanism. Otherwise, the OLC is set equal to the ILC.

Abstract: The matched nodes provide protection for a failure in the connection between two bidirectional line switched rings. They use a secondary path in case of a primary path failure. The secondary path is set aside in either the working or protection bandwidth of the rings, thus wasting resources. The invention uses inter-ring protection mechanisms which do away with a specifically set aside secondary path between the primary and secondary nodes.