PDH Over SONET/SDH: A Comprehensive Guide

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sdh
pdh
fiber optic
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This section of the SDH/SONET tutorial explains PDH concepts and the various PDH rates, including 2Mbps, 8Mbps, 34Mbps, and 140 Mbps.

PDH (Plesiochronous Digital Hierarchy) traffic, such as DS-1, E1, DS-1C, DS-2, and DS-3, is encapsulated with extra framing bytes/octets. This encapsulation allows the PDH traffic to be carried over an SDH/SONET channel.

This encapsulation is achieved using Virtual Tributaries (VT) in SONET and Virtual Containers (VC) in SDH. This means we can carry multiple DS-1 signals over a single SDH channel. For instance, 28 DS-1 signals can be carried on a single STS-1.

The term “Plesiochronous” is used because each multiplexer in the system uses its own clock for operation. ITU-T has finalized different series of recommendations for PDH. The G-series focuses on transmission systems and multiplexing equipment. The O-Series details measuring equipment specifications, and the M-Series covers transmission system maintenance.

The following rates are derived from the PDH base rate of 2.048Mbps, as described in the table below. These standards are finalized by ITU-T.

Hierarchy typeStandardBinary Rate(ppm)Line CodeAmplitudeAttenuation
1G.704/7322048kbit/sec +/- 50 ppmHDB32.37 V to 3V6dB
2G.7428448 kbit/sec +/- 30 ppmHDB32.37 V6dB
3G.75134368 kbit/sec +/- 20 ppmHDB31.00 V12 dB
4G.751139264 kbit/sec +/- 15 ppmCMI1 V12 dB
SDH Frame Structure: A Comprehensive Tutorial

SDH Frame Structure: A Comprehensive Tutorial

Explore the SDH frame structure in detail, covering STS-1, interleaving, transport overhead, and payload overhead. Understand how data is organized and transmitted.

sdh
sonet
frame structure
Fiber Optic Communication Tutorial

Fiber Optic Communication Tutorial

Learn the basics of fiber optic communication, including components, benefits, optical transmitters/receivers and losses in the fiber optic system.

fiber optic
communication system
optical transmitter