Synchronous Digital Hierarchy

What Does Synchronous Digital Hierarchy Mean?

Synchronous digital hierarchy (SDH) is an international technology standard that utilizes light-emitting diodes (LED) or lasers for synchronous optical fiber communication.

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SDH was developed to eliminate synchronization issues and replace the plesiochronous digital hierarchy (PDH) system for bulk telephone and data exchange.

Techopedia Explains Synchronous Digital Hierarchy

During the early 1990s, SDH and synchronous optical networking (SONET) ignited an optical fiber industry movement. SDH/SONET were engineered for widely sourced circuit-mode communication transport–for example, digital signal 1 (DS1)—and encoded voice support via pulse-code modulation (PCM).

SDH/SONET specifications are described in Telcordia Technologies Generic Requirements GR-253-CORE, which is respected by many global standards organizations.

Telcordia GR-499-CORE includes general criteria associated with SONET and other transmission systems, for example, asynchronous fiber optic and digital radio.

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Margaret Rouse

Margaret Rouse is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical, business audience. Over the past twenty years her explanations have appeared on TechTarget websites and she's been cited as an authority in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine and Discovery Magazine.Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages. If you have a suggestion for a new definition or how to improve a technical explanation, please email Margaret or contact her…