What are the advantages of SONET over PDH?

Answer 1

•Plesiochronous Digital Hierarchy (PDH) is the original standard for telephone network, now abandoned in favor of SONET/SDH • Exploits Time Division Multiplexing

• Designed to support digital voice channels at 64kb/s

•No store and forward: imposes strict synchronization between TX and RX. A "plesio-synchronous" (almost synchronous) solution is adopted

• Different standards in US/Europe/Japan

SONET:

•Synchronous optical networking is a method for communicating digital information using lasers or light emitting diodes (LEDs) over optical fiber.

•SONET was introduced to handle large amount of telephone calls and interoperability between equipments of different vendors.

•Synchronous networking differs from PDH in that exact rates that are used to transport the data are highly synchronized across the entire network, made possible by atomic clocks.

Answer 2

The SDH is an international standard that is highly popular and used for its high speed data transfer of the telecommunication and digital signals. This synchronous system has been specially designed in order to provide a simple and flexible network infrastructure. This system has brought a considerable amount of change in the telecommunication networks that were based on the optical fibers as far as performance and cost were concerned.

The weaknesses that PDH faced paved way for the introduction and use of the SDH systems. Although the PDH proved to be a breakthrough in the field of digital transmission, the weaknesses that made it less demanded includes:

1. Asynchronous structure that is rigid.
2. Restricted management capacity.
3. Non availability of world standard on the digital formats.
4. No optical interfaces world standard and without an optical level, networking is not possible.

But if we compare the PDH system with that of the SDH system, the latter one has a large number of advantages. Some of the most common advantages enjoyed by the usage of SDH include:

1. optical interfaces
2. capability of powerful management
3. world standard digital format
4. synchronous structure is flexible
5. cost effective and easy traffic cross connection capacity and add and drop facility
6. reduced networking cost due to the transversal compatibility
7. forward and backward compatibility