PDH Optical Multiplexer Wiki

PDH Multiplexer, or Plesiochronous Digital Hierarchy multiplexer, is a kind of point-to-point optical transmission equipment used to transport large quantities of data over digital transport media, such as fiber-optic and microwave radio systems. PDH Multiplexer is designed of highly integrated structure and provides 16 standard E1 interfaces together with one channel of order wire, with self-contained alarm and NM functions, as well as self-testing and E1 loop-back testing functions. The device is popularly with telecommunication operator. It is suitable in business for communication operator, government and kinds of entities.

PDH was developed in the early 1960s. It derives its names from the Greek term “plesio,” meaning near, and “chronos,” meaning time. The name refers to the fact that networks using PDH run in a state of almost, but not quite, perfect synchronization. PDH was the first standardized multiplexing hierarchy based on time-division multiplexing. It works by channeling numerous individual channels into higher-level channels.

Work Theory Of PDH Multiplexer
The PDH system is based on the theory that if you have two identical clocks, each the same brand, style and everything, there is no guarantee that they will run at the exact same speed. Chances are that one of them will be slightly out of synchronization with the other. The transmitting multiplexer combines the incoming data streams, compensates for any slower incoming information, reconstructs the original data and sends it back out at the correct rates. This system allows for that slight variation in speed and corrects it during transfer to keep the system constantly running without pausing and waiting for certain slower data to arrive before sending it on. PDH simply fills in the missing bits to allow for a smooth transfer of data.

PDH made little provision for management of the network, and the need to fully de-multiplex a high level carrier to extract a lower level signal meant that increasing the capacity of PDH networks beyond a certain point was not economically viable. The main economic factor was the cost of the equipment required at each cross-connect point within the network where either individual channels or low-level multiplexed data streams might need to be extracted or added. It also added additional latency and increased the possibility of errors occurring, thereby reducing network reliability.

Available Types Of PDH multiplexer
Traditionally, each channel in PDH was a digitized voice, but video information and data may also be sent over these channels. The basic channel is 64 Kbits per second, which is the bandwidth that is required to transmit a voice call that has been converted from analog to digital.

N*E1 PDH Fiber Optic Multiplexers use the PDH fiber transmission technologies. The 2M (E1) interfaces can connect with the exchanger, light loop device and multi-diplexer directly to form the micromini or the special network. Complete alarm function for N*E1 PDH Fiber Optic Multiplexers, it is stable, easy to maintenance and install, small in size. It can support one digital service telephone.

PDH Multiplexer can multiplex 4/8/16E1, Ethernet Media Converter (2*10/100Mbps) and V.35 signals in one fiber channel to transmit. It is suitable for low capacity, point-to-point application of remote transmission. The PDH Multiplexer can be applied to construct economical and flexible multi-service transmission networks, used for relay between switch offices, data transmission of LAN, 2M access of lease service for key clients, voice cutover for residental areas/intelligent buildings, and connection of base stations and other various digital transmission networks. Fiber Optic Multiplexer is reliable, stable, easy to install and maintain, which can be monitored from Fi-view-MST management software, which is widely used in voice and data application field.

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