In the digital transmission system, there are two kinds of digital transmission series, one is called “quasi-synchronous digital series”, referred to as PDH, also called pdh multiplexer, pdh multiplexer is a small-capacity optical transceiver, pdh multiplexer is generally used in pairs, also called point-to-point For point applications, the capacity of pdh multiplexers is generally 4E1, 8E1, 16E1; the other is called “Synchronous Digital Series”, referred to as SDH. So, what is a pdh multiplexer? What are the advantages of pdh multiplexer? Next, let’s to learn more about it!
Definition of pdh multiplexer
The system using the quasi-synchronous digital series (pdh multiplexer) is to set high-precision clocks on each node of the digital communication network, and the signals of these clocks have a unified standard rate. Although the accuracy of each clock is high, there are always some small differences. In order to ensure the quality of communication, it is required that the difference of these clocks cannot exceed the specified range. Therefore, this synchronization method is not strictly speaking true synchronization, so it is called “quasi-synchronization”.
In the past telecommunication networks, PDH equipments were mostly used. This series has better adaptability to traditional point-to-point communication. With the rapid development of digital communication, there are fewer and fewer direct point-to-point transmissions, and most of the digital transmissions have to be switched. Therefore, the PDH series cannot meet the needs of the development of modern telecommunication services and the management of modern telecommunication networks. need. SDH is a transmission system that emerges to meet this new need.
What is pdh multiplexer?
The earliest concept of SDH was proposed by the Bell Institute of Communications in the United States, called Optical Synchronous Network (SONET). It is an organic combination of high-speed, large-capacity optical fiber transmission technology and highly flexible intelligent network technology that is easy to manage and control. The original purpose is to achieve standardization on the optical path, so that the products of different manufacturers can communicate with each other on the optical path, thereby improving the flexibility of the network.
In 1988, the Consultative Committee for International Telegraph and Telephone (CCITT) accepted the concept of SONET and renamed it “Synchronous Digital Hierarchy (SDH)”, making it applicable not only to optical fiber, but also to the technical system of microwave and satellite transmission, and made it The network management function is greatly enhanced.
Advantages of pdh multiplexer
1.The unified bit rate and the unified interface standard provide the possibility for the interconnection between devices of different manufacturers.
2.The network management capability is greatly enhanced.
3.A new concept of self-healing net is proposed. The ring network form with self-healing protection ability composed of SDH equipment can automatically restore normal communication through the self-healing network when the main signal of the transmission medium is cut off.
4.The use of byte multiplexing technology makes the upper and lower branch signals in the network very simple.
Since PDH has the above-mentioned remarkable advantages, it will become one of the basic technologies for realizing the information superhighway. But in the branch road and fork road connected with the information highway, pdh multiplexer equipment will still be useful.
PDH multiplexer (Plesiochronous Digital Hierarchy, quasi-synchronous digital series) is a small-capacity optical transceiver, which is generally used in pairs, also called point-to-point applications.