Dense Wave Division Multiplexing, DWDM

Listen to the network pulse

Dense Wave Division Multiplexing (DWDM) is the technology, where one optical fiber is used for transmission of several signals with various wavelengths. 

The essence of technology of dense wavelength division multiplexing (or optical multiplexing) is in the possibility of organization of many separate SDH-signals that are transmitted through the single fiber, therefore, in the possibility to increase carrying capacity of a communication line in many times.

Schematic Diagram of DWDM

In order to organize several optical channels in the single fiber it is necessary to change wavelength for each SDH-signal. Then these signals are mixed with the help of a multiplexer and transmitted to the optical line. The reverse operation is made at the end point — the received SDH-signals are selected from the aggregate (composite) signal with the help of a demultiplexer; then they are transmitted to a consumer.

In the course of transmission through the optical fiber, the signal gradually fades out. In order to amplify the signal, optical amplifiers are used. Such technology makes it possible to transmit the data to the distances up to 4,000 km without necessity to transform an optical signal into an electric one.

Characteristics and advantages of DWDM technology.

DWDM technology is the most comprehensive and economically rational method of broadening of the bandwidth of fiber optic communication channels  by hundreds of times. It is also possible to increase carrying capacity of optical lines based on DWDM systems by gradually adding new optical channels to the already existing equipment in the course of future development of the network. DWDM is not only the means for increase of carrying capacity of an optical fiber; it is the most reliable technology for supporting infrastructure of multi-service and mobile communication networks; this technology ensures a drastic increase of carrying capacity of the network and ensures offering of the wide assortment of the principally new services in the sphere of telecommunication. DWDM is a rapidly evolving technology, which makes it possible to increase capacity of a single fiber from 8 up to 64 and more optical channels (wavelengths) with the following distances between the channels: 0.4, 0.8, 1.6, and 3.2 nm.

In practice, any network operator is interested not only in the number of optical channels. There are more important factors for the network operators: aggregate (total) carrying capacity of the fiber optic communication line (FOCL), as well as possibility of further increase of carrying capacity of the FOCL in accordance with growth of market demands. It is DWDM technology, which lets to ensure carrying capacity of such systems — 400 Gbit/s with frequency spectrum at the level of 100 GHz and connection of STM-64 to each channel. The most essential advantage of DWDM technology is connected with the possibility of substantial increase of carrying capacity without changing of electronic equipment and optical cable (new channels with new wavelengths) and without interfering to the already existing ones. The point is that increase of carrying capacity is possible not for several percentage points, but by dozens and hundreds times. The channels may have different protocols and transmission speeds, and there is no necessity to synchronize them with each other. TDM technology may be applied in respect of each WDM channel; this makes it possible to allocate the bandwidth among consumers in the more flexible manner. Many national and international operators have recognized long ago that DWDM technology is the most optimal decision for transmission of powerful data flows to big distances.

The equipment based on the DWDM technology is used not for creation of new fiber optic communication networks; it is used for modernization and broadening of the already existing networks with the purpose of essential increase of their carrying capacity and accessibility.

Another advantage of DWDM technology is connected with a quick payback of the funds invested by operators to implementation of this technology and with profit earning due to this technology. There is no necessity for operators to lay new lines, which always result in additional expenses and problems.

In the final analysis, expenditures for purchase of the equipment, which is necessary for implementation of DWDM technology (terminal optical wave transmitters, amplifiers, filters, network management equipment, as well as complexes of the ridged planar waveguides, which ensure demultiplexing of signals at the receiving end of transmission line), are  much less the expenditures, which are necessary for development of a new network.

The Projects that Are Already Implemented

Upgrade and expansion of MTS Ukraine DWDM transport network

Building a National Optical Network for Beeline. First Stage

Development of DWDM-network of "Ucomline" Closed Joint-Stock Company at the "Kyiv-Lviv" section on the basis of the equipment manufactured by Cisco Systems Company

Development of a section of the backbone network with the help of utilization of DWDM-technology for UMC

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