Add-drop multiplexer

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Add-drop multiplexer for SONET / SDH

An add-drop multiplexer is a device of multiplex technology that can add one or more partial signals to a multiplex signal (add) and also remove partial signals from the multiplex signal (drop). The received multiplex signal is sent on unchanged except for these add / drop changes.

The add-drop multiplexer is therefore an extension of the conventional multiplexer , which is only used as a terminal multiplexer at the end of transmission links.

use

The add-drop multiplexer is used as a network element in the course of linear transmission links or in ring-shaped network arrangements.

There it decouples one or more of the partial signals contained therein from the aggregate-side signals ( STM-1 , STM-4, ...) and makes them available to its subscriber connections. From there they are forwarded to subordinate network elements in the network hierarchy.

In the opposite direction, it inserts tributary signals (adj. Tributary = inflowing), which originate from subordinate network elements, as partial signals into the signals on the unit and thus ensures that they are forwarded via the interfaces in the network.

Terminal multiplexer

If a device using SDH technology is able to completely break down a multiplex signal into its individual partial signals or to create a multiplex signal from these, it is called a terminal multiplexer . The terminal multiplexer is required in SDH networks at the end of linear routes . There it combines incoming signals ( tributary signals ) that originate from hierarchically subordinate network elements into an aggregate signal , which it forwards into the network.

The add-drop multiplexer is an extension of the terminal multiplexer. While this has only one interface on the aggregate side, the add-drop multiplexer has two STM interfaces with the same hierarchy level.

technology

Add-drop multiplexers have become possible for the first time with SDH technology. In PDH technology, for reasons of synchronization it was still necessary to first break down the entire received multiplex signal into all of its individual partial signals, in order to then add a new partial signal after resynchronization.

See also