3.1 Introduction

Extraordinary demand for high-speed, high-performance networks with vast transmission capacities and potentially unlimited bandwidth contributes to the popularity of SONET/SDH (Synchronous Optical Network and Synchronous Digital Hierarchy) solutions. SONET/SDH are network transport technologies that use synchronous operations for facilitating real-time voice, video, and data transmission via fiber optic cabling at rates ranging from 51.84 Mbps (OC-1 or Optical Carrier-Level 1) to 13.21 Gbps (OC-255). The need for potentially unlimited bandwidth also fosters development and deployment of next-generation WDM (Wavelength Division Multiplexing) and DWDM (Dense WDM) optical network implementations in order to support bandwidth-intensive voice, video, and data transmissions at multigigabit and multiterabit rates.

In the 1980s, standardized rates and formats for optical transmissions in SONET/SDH networks were established. SONET/SDH installations replaced proprietary optical network implementations. Deployed by Regional Bell Operating Companies (RBOCs) and Interexchange Carriers (IXCs), proprietary optical network solutions were incapable of supporting internetworking services.

Present-day SONET/SDH deployments enable high-performance networking operations and interwork with diverse broadband technologies. ATM (Asynchronous Transfer Mode) and SONET/SDH are complementary technologies. In typical broadband installations, ATM functions in a switching and multiplexing capacity and SONET/SDH serve as the underlying Physical Layer transport technology.

ATM-over-SONET/SDH implementations support a rich array of tele-education and teleresearch initiatives. Despite their capabilities, SONET/SDH solutions exploit only a small fraction of the available capacity of the existing fiber optic plant. This operational constraint contributes to the development of next-generation WDM and DWDM optical networks.

WDM and DWDM systems employ multiple wavelengths for enabling transparent networking services that...