Optimization of protection bandwidth of four fiber bidirectional line switched ring

The SONET/SDH Rings are deployed by the Telecom Service Providers since a long time. The Four Fiber Bi-directional Line Switched Ring (4F BLSR), a kind of SONET Ring having a strong protection capability, keeps two fibers aside for protection that remain idle or are used for very low priority Extra Traffic. This paper describes how this protection bandwidth can be effectively utilized without any extra hardware. The idea is to add a Two Fiber Bi-directional Line Switched Ring (2F BLSR) on the two fibers that are set aside for protection in 4F BLSR. Thus, the vast Protection Bandwidth in a 4F BLSR can survive a failure in a span. This paper analyzes all the aspects in a BLSR configuration to show the effectiveness of the new combined 4F and 2F BLSR. This new configuration will provide a very high degree of flexibility on the widely deployed classical SONET Rings.