WDM Full Form is Wave Division Multiplexing. With an increase in data usage globally, it has become imperative to have high capacity communication using limited available transmission infrastructure. Wave division multiplexing (WDM) is a technique that helps upgrade an optical network without any overhauling to the backbone network. In WDM, multiple light signals having varied wavelengths are transmitted using the same optic fiber, thereby eliminating the need to use multiple fibers.
The technique uses a device called multiplex at the source (transmitter) which joins several light signals having multiple wavelengths together. The combined light signal is then transmitted via optic fiber and then at the receiving end there is a device called a de-multiplexer which again splits the light signal to the original wavelengths. For transmission of the optical signals to longer distances, optical amplifiers are used. Depending on the wavelength patterns the WDMs can be divided as Coarse WDM and Dense WDM.
The two differ in the spacing of the wavelengths, number of channels, and the sophistication level of the optical amplifiers. Coarse WDM provides around 16 channels while Dense WDM can provide 40 or 80 channels depending on the kind of multiplexing and amplification techniques used. Coarse WDM are generally cheaper as compared to the Dense WDM.