Synchronous optical network (SONET) is ANSI standard whereas Synchronous digital hierarchy (SDH) is ITU-T standard. SONET/SDH is a synchronous network. Single clock is used to handle the timing of transmission and equipment across the entire network so it adds a level of predictability to the system.—improved speed and reducing cost. SONET/SDH contains recommendations for the standardization of fiber optic transmission equipment (FOTS). SONET/SDH physical specification and frame design include mechanism that allow it to carry signals from incompatible tributary systems (e.g. asynchronous services –DS-0 and DS-1) SONET is a multiplexed transport mechanism and can be a carrier for broadband services e.g. ATM and B-ISDN. SONET defines a hierarchy of signaling levels called synchronous transport signals (STSs). The physical links defined o carry each level of STS is called Optical Carriers (OCs). OC describe the conceptual and physical specification of the links required to support each level of signaling.
view / download: SONET-SDH (size 509 KB)