Summary: SDH is very useful equipment that is used for the telecommunication sector in easy transfer of data. Earlier PDH was widely used but due to some of its weaknesses, SDH has replaced the use of PDH.

Communication systems, technology, and applications in today’s information world. Jay z no hook acapella music awards. B ENEFITS OF F IBER O PTICS Optical fiber systems have many advantages over metallic-based communication. Optical communication and networks Notes Download pdf, ECE 7th Semester Electronics and Communication Engineering. As per Anna university syllabus of regulation 2013 as well we provided important 2 marks and 16 marks questions with answer for all units.

But not everywhere. Point to Point applications are still used mainly by PDH, and also, it’s cheaper. PDH or the plesiochronous digital hierarchy is a popular technology that is widely used in the networks of telecommunication in order to transport the huge amounts of data over the digital equipment for transportation like microwave radio or fiber optic systems. The term plesiochronous has been derived from the Greek work ‘plesio’ that means ‘near’ and ‘chronos’ meaning time. This means that the PDH works in a state when the various different parts of a network are clearly synchronized. But with the change in technology, the PDH is now being replaced by the SDH or what is popularly called as synchronous digital hierarchy. The SDH is useful equipment that is used in most of the telecommunications networks.

This PDH helps in proper transmission of the data that generally runs at the similar rate but allows some slight variation in the speed than the nominal rate. The basic transfer rate of the data is 2048 kilobits per second.

For instance, in each speech transmission, the normal rate breaks into different thirty channels of 64 kilobits per second along with two different 64 kilobits per second in order to perform the tasks of synchronization and signaling. The typical rate of transmitting the data over the fiber optic systems is 565 Mbit/sec in order to transport the data in the long distance. But as the technology has improved with the passing of time, now the telecommunication companies have replaced the PDH equipment with that of the SDH equipment, which has the capability of transmitting the data at much higher rates as compared to the PDH system. 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: • Asynchronous structure that is rigid. • Restricted management capacity. • Non availability of world standard on the digital formats. • No optical interfaces world standard and without an optical level, networking is not possible.