Synchronous Optical Network [SONET]


(pronounced “SAH-net”) (n.) A broadband networking standard based on point-to-point optical fiber networks. The standard provides a high-bandwidth pipe to support services based on Asynchronous Transfer Mode (ATM). SONET establishes a digital hierarchical network with a consistent transport scheme. It has been optimized for fiber, in contrast to the plain old telephone system (POTS), which was designed for copper wires. SONET carries circuit-switched data in frames at speeds up to 48 gigabits per second (Gbps) in multiples of 51.84 megabits per second (Mbps). Each SONET frame is a two-dimensional table of bytes 9 rows high and 90 columns deep. Groups of frames are called superframes.

Data transfer rates at different levels of SONET are shown below:

OC Line | Rate | Capacity Level

OC-1  52 Mbps  28 DS-1 or 1 DS-3

OC-3  155 Mbps  84 DS-1 or 3 DS-3

OC-9  466 Mbps  252 DS-1 or 9 DS-3

OC-12  622 Mbps  336 DS-1 or 12 DS-3

OC-18  933 Mbps  504 DS-1 or 18 DS-3

OC-24  1.2 Gbps  672 DS-1 or 24 DS-3

OC-36  1.9 Gbps  1008 DS-1 or 36 DS-3

OC-48  2.5 Gbps  1344 DS-1 or 48 DS-3

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