Chapter 9 - Optical Network Survivability

Abstract

This chapter gives a brief overview of optical network survivability. Engineering the network for survivability plays an increasingly important role in transport networks. Protection techniques are well established in Synchronous Optical Networking (SONET) and Synchronous Digital Hierarchy (SDH) and include point-to-point, dedicated protection rings, and shared protection rings. Point-to-point protection schemes work for simple systems with diverse fiber routes between node locations. In addition, optical channel layer protection is needed if some channels are to be protected while others are not. Optical multiplex section (OMS) layer protection is more cost effective for those cases where all the traffic needs to be protected. The optical layer consists of the optical channel layer (or path layer), the OMS layer (or line layer), and the optical transmission section layer. The choice of protection schemes is dictated primarily by the service classes to be supported and by the type of equipment deployed. In the SONET/SDH world, protection is performed primarily by the SONET/SDH line terminals and add/drop multiplexers and not by digital cross connects.