WDM (Wavelength Division Multiplexing)

What is WDM? – Basics of our CWDM & DWDM system

The IT refers to a medium where information is transmitted via a link. If two locations want to communicate with each other, one link is sufficient. To connect more locations more links are required What if only one link e.g. between two cities is available, but more applications shall be connected? Using the WDM technology, fiber optic links can be utilized for data transmission more efficiently.

WDM basics
WDM basicsClick on the image to enlarge

The idea of xWDM technology

Each application is allocated to a dedicated color (wavelength) to communicate with a remote station. The advantage is that different colors can be simultaneously transmitted using one pair of fiber. For this purpose a multiplexer combines all different colors which will then be transmitted to the remote station over one pair of fiber. At the remote site the combined signal is separated again into different colors by a demultiplexer. Generally only one light beam with one wavelength is transferred over a pair of fiber. The wavelength multiplexing technology provides the ability to transmit more light beams, each having different wavelengths, using the same optical link. Due to the fact that wavelengths do not interfere, single light beams can be separated from each other using simple filters. A laser serves as the source of light and light-sensitive diode as receiver unit. Wavelength multiplexing is differentiated in CWDM (Coarse Wavelength Division Multiplexing) and DWDM (Dense Wavelength
Division Multiplexing) technology. Advantage: With the use of WDM, it is possible to transfer nearly 1 Tbps (C-band) via one pair of fiber today.

Choosing of the appropriate wavelength

By the use of appropriate transceivers (SFP, XFP etc.) with different power budget ranges from a few 100 m up to 160 km can be achieved. A major factor in the range is – next to the power budget of the transceiver – the used wavelength as a fiber has a specific attenuation behaviour for each wavelength. The higher the attenuation, the lower the overall distance. With a careful selection of the wavelength a higher range and better signal quality can be achieved.

LossClick on the image to enlarge
Optical bands
Optical bandsClick on the image to enlarge

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