Digital multiplexers are logical combined devices that are designed for the controlled transfer of information from several data sources to a single output channel. In fact, such a device is a few digital position switches. Accordingly, we can conclude that the digital multiplexer is a switch of input signals to one output line. This article will consider a separate type of instrument - optical SDH multiplexers.
Such devices are designed to work with data streams using light beams, which differ in amplitude or phase diffraction grating, as well as wavelength. SDH multiplexers transmit information on E1 channels and Ethernet lines in transport fiber networks. They operate on one or two optical fibers (single-mode or multimode) with a speed of 155.520 Mbit / s at a wavelength of 1550/1310 nm. SDH multiplexers allow you to implement up to 126 points of communication.
The advantages of such devices include resistance to external influences, technical safety, protection against hacking of transmitted information.
SDH multiplexers can be easily scaled by including up to three additional modules for transmitting Ethernet channels, E1 streams, intercom, and the PM channel in the main module.
These devices are characterized by high survivability of the network. The implementation of E1 streams has a low jitter value, due to this, the norms for E1 are observed during synchronization drift, as well as in case of STM-1 system synchronization failure. The interface parameters allow you to track the error in the communication channel and switch to the spare channel. The optical path and power are reserved according to the 1 + 1 scheme. That is, when working on a single fiber channel, in case of cable damage, communication between subscribers is maintained.
SDH multiplexers can easily be combined with other equipment such as SDH. They can work both in synchronous and in asynchronous modes; multimode and single-mode optical fibers are allowed. The SDH multiplexer supports the remote configuration and control function over TCP / IP, 10/100 BaseT.
Such switching devices are usually divided into two types: terminal and input / output. The difference between these types is not in the composition of the ports, but in the placement of the device in the SDH network. The terminal multiplexer completes the aggregate channels, switching among them a large number of output and input channels. The second type of devices transits aggregate lines in transit, occupying an intermediate position on the highway. In this case, tributary channel information is derived from the aggregate stream or entered into it.
Most manufacturers produce universal multiplexers of the SDH type, which are used as input / output, terminal, as well as cross-connectors, depending on the modules installed in them with tributary and aggregate ports.
In conclusion, we add that fiber-optic multiplexers are gaining more and more popularity due to the intensive development of this type of communication. The future lies in fiber optic technology.