摘要：

From the Book: To meet the need for the transport of broadband services such as broadband ISDN, ATM, HDTV and SMDS for years to come, national SONET standards have been developed by national standards bodies. SONET is supported by multiple entities including Bellcore, RBOCs (Regional Bell Operating Companies), other LECs (Local Exchange Carries), global Telecommunications Administrations (TAs), and major telecommunications vendors cross the world. The SONET/SDH Phase 1 standards were approved by ANSI and ITU-T (at the time, CCITT) committee members in 1988. Since then, the North American digital network has been gradually transformed into a SONET-based network. On the other hand, outside the North American digital network, SDH standards have also been rapidly implemented and deployed to coexist with existing PDH networks. The new global digital network (implemented by SONET/SDH standards) has several characteristics which can not be found in the traditional PDH digital (public or private) network. For example, the SONET/SDH network are reliable, fully manageable, flexible and easy to grow due to the modular characteristics of SONET/SDH signal rates/formats, the abundant capacity for network management functionality, and the utilization of high bandwidth and excellent optical fiber network facilities. The SONET (Synchronous Optical NETwork) standards was proposed in the United States of America in the early 1980s. It was introduced to the ANSI T1 committee by Bellcore in 1985. SONET was then modified for ITU-T (International Telecommunications Union - Telecommunications Standardization Sector, which if the new name for CCITT) applications. Globally, its name has also evolved from SONET to assumea new name, SDH (Synchronous Digital Hierarchy). However, SONET and SDH are technically consistent. The major difference between them is in their terminologies. For example, a SONET OC-3 signal is very much the same as a SDH STM-1 signal. The network management functions of SONET and SDH are practically identical. For frame synchronization, both SONET and SDH apply a frame pattern of F628 Hex, which is carried by A1 and A2 bytes; and, for orderwire purpose, they both use the E1 byte for a regenerator section as a message channel. From network management perspective, many parallels can be drawn between SONET and SDH. SONET/SDH related products are expected to be provided by vendors and used in telecommunications networks all over the world. The SONET/SDH product lines include Digital Cross-connect Systems (DCSs), Add/Drop Multiplexers (ADMs), Integrated Digital Loop Carrier (IDLC) systems, switches and regenerators. This equipment is built with the full network management capabilities that are recommended by the SONET/SDH standards. As a result, vendor proprietary characteristics have been eliminated in this SONET/SDH-based global digital network and replaced with a more open architecture. This book is a product of my research, and teachings in optical fiber communications for digital transmission applications throughout the years [at AT&T, AT&T-Bell Laboratories, GIS (USA, Europe and Asia), NET, China, TL-Taiwan, ALTTC-India, University of Puerto Rico, and Fairleigh Dickinson University]. I have been providing instruction in the SONET/SDH area since April 1989, which is about six months after ANSI and CCITT adapted SONET/SDH as a communication standard protocol worldwide. My audiences have included corporate managers, project managers, sales and marketing teams, engineers, system designers (hardware and software), technicians, and educators. Hence, this book is written for a broad array of readers. SONET/SDH technology is still evolving. Current standards are robust enough to design SONET/SDH products. There are issues, in the areas of applications, which still need to be addressed and resolved. The SONET/SDH documentation listed in the references will continue to be modified and revised. Any newly added and/or modified protocols are expected to be implemented by software. This book has appeared in various formats throughout the pa

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