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Synchronous Digital Hierarchy |
SDH, the synchronous digital hierarchy, is the international counterpart of SONET. SDH is widely used in European countries. Signals in SDH are called synchronous transport modules, which are designated STM-N. The basic STM signal, STM-1, transmit at 155.52 Mbit/s, it is the same rate as which OC-3 transmit.
SDH only has small differences with SONET. Combined with other technologies like WDM, ATM and Internet, SDH play more and more important role in the communications filed. SDH is well acknowledged as the future trend of digital communication with bright commercial application value.
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