Synchronous Optical Network

(sonnet)

An ANSI standard originally proposed by Bellcore in the mid-1980s and used for connecting fiber-optic transmission systems. SONET is a physical layer (see OSI) process. By specifying standard data rates carriers across the world can interconnect.

SONET was designed specifically for fiber-optics. Many other transmission standards have been adapted but were originally designed for plain old telephone system copper wires.

SONET carries switched data in frames. Speeds are multiples of 51.84 megabits per second up to times 48 (2.488 gigabits per second). Multiple channels are used so think of a SONET frame as a table of bytes 9 rows by 90 columns. SONET can transmit "n" frames per unit time for every OC-n level. When frames are grouped a superframe results.

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