Alcatel-Lucent 1643 AMS - Appendix A: An SDH overview; Overview

Appendix A: An SDH overview
Overview
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Purpose
This chapter briefly describes the Synchronous Digital Hierarchy (SDH).
Synchronous Digital Hierarchy
In 1988, the ITU-T (formerly CCITT) came to an agreement on the Synchronous
Digital Hierarchy (SDH). The corresponding ITU-T Recommendation G.707 forms the
basis of a global, uniform optical transmission network. SDH can operate with
plesiochronous networks and therefore allows the continuous evolution of existing
digital transmission networks.
The major features and advantages of SDH are:
• Compatibility of transmission equipment and networks on a worldwide basis
• Uniform physical interfaces
• Easy cross connection of signals in the network nodes
• Possibility of transmitting PDH (Plesiochronous Digital Hierarchy) tributary signals
at bit rates commonly used at present
• Simple adding and dropping of individual channels without special multiplexers
(add/drop facility)
• Easy transition to higher transmission rates
• Due to the standardization of the network element functions SDH supports a
superordinate network management and new monitoring functions and provides
transport capacity and protocols (Telecommunication Management Network, TMN)
for this purpose in the overheads of the multiplex signals.
• High flexibility and user-friendly monitoring possibilities, e.g. end-to-end
monitoring of the bit error ratio.
Purpose of SDH
The basic purpose of SDH is to provide a standard synchronous optical hierarchy with
sufficient flexibility to accommodate digital signals that currently exist in today’s
network, as well as those planned for the future.
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365-312-801R7.2
Issue 3, May 2007
Alcatel-Lucent - Proprietary
See notice on first page
A-1