Introduction of SDH Technology

Synchronous Digital Hierarchy (SDH) is a hierarchy pemultiplekan based on synchronous transmission that has been defined by CCITT (ITU-T). In the world of telecommunications, pemultiplekan series of signals in the transmission poses problems in terms of branching and insertion (drop and insert) that is not easy, and limitations to monitor and control the transmission network.
Before the emergence of SDH, the existing transmission standard known as PDH (Plesiochronous Digital Hierarchy), which has long been defined by CCITT. A network does not synchronize plesiochronous network but using only pulses beat (clock) that is very accurate in all the nodes penyakelarnya (switching nodes) so that the rate of slip between the various nodes are quite small and still be acceptable (eg plus / minus 50 bits or 5x10 -5 to network / channel 2.048 or 1.544 Mbps). This mode of operation such as this may indeed be a most simple implementations because they are avoiding the distribution of timing throughout the network.
It turns out that PDH is not so well suited to support the development of control techniques and signal processing for today are increasingly needed by companies of telecommunications service providers. In PDH, a certain transmission equipment generally only deal with either one specific function within the network, while in a SDH, there is the integration of various types of different equipment that can provide new freedom in designing the network. It's not a new news that the SDH can be used for large capacity optical transmission, traffic regulation and restoration of communications networks.
SDH has two main advantages: flexibility so high in terms of channel configurations on both nodes network and improve network management capabilities for both its payload traffic and network elements. Taken together, these conditions will allow the network to be developed from the passive transport structures in the PDH into other tissues that actively transports and organize information.
Specific offers are created by the SDH of which include:

    * Self-healing; the redirection (rerouting) communication traffic automatically without interruption of service.
    * Service on demand; provision of rapid end-to-end customer services on demand.
    * Access is flexible; flexible management of various lebarpita remains to places customers.
SDH standards also help the creation of an open network structure, much needed in today's competitive scope for companies of telecommunications service providers.

 Source: h**p://elektroindonesia.com/elektro/telkom11a.html