SONET (Synchronous Optical NETwork) A set of North American standards for broadband digital transmission over single-mode fiber (SMF) optic transmission systems (FOTS), SONET grew out of the SYNTRAN (SYNchronous TRANsmission) standard developed at Bellcore. SONET was initially developed in 1984 and finally standardized by the American National Standards Institute (ANSI) in 1988. Also in 1988, SONET was internationalized by the ITU-T as Synchronous Digital Hierarchy (SDH), which differs primarily with respect to low-level line rates and some terminology. SONET/SDH essentially is a broadband optical version of T-carrier, defined in multiples of T3 bandwidth plus overhead for additional signaling and control functions. Primarily intended for carrier backbone implementation, SONET/SDH 74570c19.qxd 9/12/07 12:41 AM Page 450 |