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A Tutorial on ITU-T G.709 Optical Transport Networks (OTN)

The SONET/SDH network that has grown to be the backbone of most of the modern telecommunications network was originally designed for optical interfaces that used a single wavelength per fiber. As optical component technology has advanced, it has become more economical to transmit multiple SONET/SDH signals over the same fiber using wavelength division multiplexing (WDM) rather than going to a higher rate SONET/SDH signal. Based on experience with the SONET/SDH networks, the ITU-T defined a transport network that was optimized for cost-effective transparent transport of a variety of client signals over WDM networks. The optical transport network (OTN) architecture is specified in ITU-T Rec. G.872 and the frame format and payload mappings are specified in G.709.

This white paper provides a tutorial overview of OTN, with primary emphasis on ITU-T G.709. The white paper also discusses various constraints that influenced the development of G.709, its current status in the network, and some factors that will affect its future.

About PMC
PMC-Sierra is a leading provider of broadband communications and storage semiconductors for metro, access, fiber to the home, wireless infrastructure, storage, laser printers, and fiber access gateway equipment. PMC-Sierra offers worldwide technical and sales support, including a network of offices throughout North America, Europe, Israel and Asia. The company is publicly traded on the NASDAQ Stock Market under the PMCS symbol. For more information, visit www.pmc-sierra.com.

About the Authors
Steve Gorshe, Ph.D. is a Principal Engineer in PMC-Sierra's Chief Technology Officer's organization, working on technology for optical transmission and access systems.

Steve is a Fellow of the IEEE. He has been with PMC-Sierra since 2000, and has 26 years of experience in research and development of telecommunications systems and ICs. His previous work included holding the position of Chief Architect for NEC eLuminant Technologies. He is the current IEEE Communications Society Director of Magazines, and Associate Editor-in-Chief and former Broadband Access Series co-editor for IEEE Communications magazine. He is Chief Editor and a technical editor for multiple standards for the ATIS OPTXS Committee (formerly T1X1), which is responsible for ANSI transport network interface standards including SONET. He has is also technical editor for multiple ITU-T standards, including G.7041 (Generic Framing Procedure - GFP), G.8011.1 (Ethernet Private Line Service), and G.Sup43 (Transport of IEEE 10G Base-R in Optical Transport Networks (OTN)). He is a recipient of the Committee T1 Alvin Lai Outstanding Achievement Award and the ATIS Outstanding Contribution award for his standards work. He has 32 patents issued or pending, over 24 published papers, and is co-author of a telecommunications textbook and of two additional book chapters. Steve received his Ph.D. and MSEE from Oregon State University and BSEE from the University of Idaho.

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