High speed transport networks and synchronization techniques

High-Speed Transport mechanisms are becoming increasingly important as the demand for high bandwidth continues to grow. A number of High-Speed networks are evolved through various transport techniques like Plesiochronous Digital Hierarchy (PDH), Synchronous Digital Hierarchy (SDH), Dense Wavelength Division Multiplexing (DWDM) and Digital Wrappers. With complex architectures, synchronization of these networks becomes quite a challenging task. This paper discusses evolution of digital networks and synchronization architectures. The International Telecommunication Union (ITU) recommendation for SDH Equipment Slave Clocks (SEC) timing specification is G.813. The paper also covers implementations of SDH Equipment Slave Clocks and their timing characteristics.