PREFACE

In four previous books, we introduced the SONET and SDH communications proto-col technologies and Wavelength Division Multiplexing (WDM) as the new tech-nology of this millennium. SONET has proven its robustness and fast switching forprotection. The physical layer of SONET has served as the starting point for single-lighpath technologies, and WDM is a technology that multiplexes many lightpathsonto a single fiber. Although WDM was initially a physical layer technology fortransporting a large aggregate bandwidth and reducing the interconnecting fibers toone, recently it moved to the switching layer. WDM has been so successful that ithas become a "victim of its own success." WDM technology is being considered byall communications camps—SONET over DWDM, ATM over WDM, IP overWDM, GbE over WDM, and so on. However, if all these X over WDM technologiesmaterialize, then it is difficult to imagine an efficient network with so many over-lays and the impact on network management, protection, and service availability.

As a consequence, a network is needed that is based on a foundation with a com-mon procedure that encompasses the advantages of many technologies and proto-cols, yet removes their disadvantages. Such a network could then interface with alltraffic types (GbE, TDM, IP, and so on). Imagine also that if SONET/SDH could besimplified and enhanced, then such a procedure would be in harmony with the newSONET/SDH, and, moreover, the new SONET/SDH would be in harmony withDWDM.

If all this sounds like a mission impossible, then the skeptic will be disappointedbecause such procedures have been developed and standardized. It is the objectiveof this book to introduce the next generation SONET/SDH and to also provide a de-scription of the next generation optical network. Thus, based on technological ad-vancements, new optical systems are being designed and new optical networks de-signed. These new systems and networks offer more bandwidth at less cost, and it isexpected that bandwidth will become a commodity item.

This is the fifth book in the series of optical networking. Understanding SONET/SDH and ATM: Communications Networks for the Next Millennium (IEEE Press,1999) provides a comprehensive overview of SONET, SDH, and ATM. Introductionto DWDM Technology: Data in a Rainbow (IEEE Press, 2000) provides a high-levelintroduction to DWDM technology and how it works in DWDM networks. FaultDetectability in DWDM: Towards Signal Quality and System Robustness (IEEEPress, 2001) provides a treatise in fault mechanisms, how they correlate, and how

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they are detected. DWDM: Networks, Components and Technology (IEEE Press/Wiley) provides an in depth description of optical networks, systems and compo-nents.

This new book provides a comprehensive treatment of the next generationSONET/SDH over DWDM. It explains in simple terms many new protocols such asthe Generic Framing Procedure, and other related protocols that aim to simplify thenext generation optical network, increase its efficiency, and decrease its cost. How-ever, as each day has a "tomorrow," so each network generation has a "next" gener-ation. Thus, the fundamental question is "How long will the next generation net-work resist obsolescence"? This truly depends how fast technology will advance, ifa new disruptive technology will emerge, and how soon a new appetite for morebandwidth and new services will emerge. Clearly, if the "next generation" opticalnetwork is defined with enough flexibility and resiliency, then the probability that itwill last for a long time is high.

It is my hope that this book will excite and stimulate the interest of the reader inthe exciting Next Generation Optical Network (NGON) and will aid in the develop-ment of robust, efficient, and cost-effective systems and networks.

ACKNOWLEDGMENTS

I thank my wife, Anita, son, William, and daughter, Stephanie for consistent pa-tience and encouragement. I also thank my publishers and their staff for coopera-tion, enthusiasm, and project management. To the anonymous reviewers for usefulcomments and constructive criticism; and all those who worked diligently on allphases of the production of this book.

STAMATIOS Y KARTALOPOULOS, PH.D.