SONET/SDH

SONET is an ANSI standard for transmitting bits over fiber-optic cable. SDH is the international standard defined by the International Telecommunication Union (ITU). SONET/SDH is the physical infrastructure of choice for carrier ATM networks operating at speeds above 50 Mbps.

SONET/SDH allows carriers to build high-speed international links without requiring conversion from one transmission protocol to another (for example, T1 to T3 or T1 to E3 conversion).

SONET transmission speeds start at 51.84 Mbps and are referred to as OC1. SDH transmission speeds start at 155.52 Mbps and are referred to as STM1. All other speeds are multiples of these base numbers. Table 14 shows the speeds of the most common SONET/SDH implementations.

Table 14: Most Common SONET/SDH Implementations

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