A class of self-healing ring architectures for SONET network applications

Synchronous optical network (SONET) technology has made high-speed self-healing ring (SHR) architectures practical and economical. The SHR architectures can be divided into two basic classes: bidirectional SHR (B-SHR) and unidirectional SHR (U-SHR). The cost and capacity tradeoffs between B-SHRs and U-SHRs depend strongly on the application, the network size, and the demand pattern. B-SHRs with four fibers can be operated under today´s operations environment without a significant change. However, U-SHRs using a path protection switching method may ease intervendor compatibility problems and can be implemented on a timely basis without changing the well-defined SONET APS protocol. The selection of appropriate SONET SHR architectures will depend on the operating telephone companies´ economic analysis, emphasis on a multivendor environment, SHR implementation time frame, and standards progress on making change to support a bidirectional ring architecture