Answer / k.shanmugasiva

What is SDH ?
Synchronous Digital Hierarchy

What is PDH?
Plesiochronous Digital Hierachy

Answer / jagadesh

PDH AND SDH ARE TWO SYSTEMS OF TRANSMISSION USED IN COMMUNICATION THROUGH MICROWAVE RADIO AND FIBER OPTIC SYSTEMS.
PLESIOSCHRONOUS DIGITAL HIERARCHY (PDH)SYSTEM IS USED WHERE LOWER CAPACITY OF E1 HAS TO BE TRANSMITTED SAY UPTO 16E1 G.703.
THIS PDH SYSTEM IS USED ESPECIALLY FOR POINT TO POINT SHORT HAUL TRANSMISSION.

SYNCHRONOUS DIGITAL HEIRARCHY(SDH) SYSTEM IS USED FOR HIGHER CAPACITY TRANSMISSION SAY UPTO STM4.THIS SDH SYSTEM IS USED ESPECIALLY FOR LONG HAUL TRANSMISSION.

Answer / gomz

Plesiochronous Digital Hierarchy (PDH) system for
transporting larger amounts of telephone calls and data
traffic over the same fiber wire without synchronization
problems.

Synchronous Digital Hierarchy (SDH) is a standardized
multiplexing protocol that transfer multiple digital bit
streams over optical fiber using lasers or light-emitting
diodes (LEDs)

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