Patent ID: 7974185

Claim:
A method for arranging traffic transmission and protection in a three fiber line switched ring (3 FLSR) network of N nodes, comprising the steps of: Providing first and second fibers traversing in opposite directions and spanning the N nodes for bidirectional line switching, wherein each of the first and second fibers includes working channels for carrying primary traffic and protection channels for carrying secondary traffic; providing an only additional fiber as a third fiber connected in a single direction in clockwise or anticlockwise direction spanning all the nodes and co-operating with the first and second fibers and supporting co-existence of unidirectional line switching and bi-directional line switching, wherein each node is configured to selectively perform addition, dropping, or passing through of transmission traffic, wherein supporting the co-existence of unidirectional line switching and bi-directional line switching comprises: when one failure occurs in one of the first and second fibers of the 3 FLSR network of N nodes, initiating a span switch to carry traffic flow of the one of the first and second fibers in which the failure occurs through the third fiber thereby providing the unidirectional line switching, wherein carrying the traffic flow of the one of the first and second fibers in which the failure occurs through the third fiber includes carrying both the primary and secondary traffic of the one of the first and second fibers in which the failure occurs through the third fiber; and when two failures occur in the 3 FLSR network of N nodes, initiating a span switch to carry traffic flow affected by a first failure and a ring switch to carry traffic flow affected by a second failure thereby supporting the co-existence of the unidirectional and bi-directional line switching, wherein the two failures comprise two failures in the first fiber, two failures in the second fiber or one failure in the first fiber and other failure in the second fiber, and wherein carrying the traffic flow affected by the second failure includes carrying the primary traffic of each of the first and second fibers and loosing the secondary traffic of each of the first and second fibers; and, using the third fiber selectively for protection when there are one or two failures, and handling additional traffic in the clockwise or anticlockwise direction when there are no failures in the 3 FLSR network of N nodes.