SDH rings for distributed cross-connect functionality

SDH (synchronous digital hierarchy) based systems represent a major advance over current PDH (plesiochronous digital hierarchy) based transmission systems. The authors examine the role SDH rings play in SDH transmission systems, in particular the benefits obtained from the autonomous protection switching (APS) and distributed bandwidth management (DBM) features. An SDH ring deployment strategy is described showing how SDH rings can be used in conjunction with cross-connects to build high speed transmission networks that are flexible, survivable and cost effective