Wavelength Division Multiplexing (WDM)

Before discussing Wavelength Division Multiplexing, let discuss wavelength. Wavelength is the distance that is between two repeating units of a particular wave given that it is measured from one point to another corresponding point. For instance, the distance of the top part of a wave, known as the crest, to the other crest is considered to be one full wavelength. Different colors have different wavelengths and as a result different penetration ability. In physics, is designated a Greek letter called lambda. It is usually proportional to the frequency of a wave. This is to mean that the shorter the wavelength, the more waves you expect to have to pass a particular point on a given time.

With that basic background, we can comfortably move to the use of wavelengths in today’s communications technology. This wavelength basic is used in devices that are known as Wavelength Division Multiplexing (WDM). These are devices, electronic, that combine the light signals that have different wavelengths, coming from different fibers into one fiber. They are a very cost-effective way to expand the capacity of the already existing cables.

How WDM works

The following is an overview of how WDM’s work

  • They start out using the phenomenon of the light waves, where the natural light contains all colors of light that are transmitted together and can easily be separated using a prism.
  • In a fiber cable, many wavelengths can be sent through the cable at the same time by the use of a coupler of a multiplexer. This combines the different wavelengths.
  • At the other end, however, there should be a demultiplexer that will work like a prism to disperse the different wavelengths into the fiber cables that are waiting. The wavelengths are sent off in different directions by the demultiplexer.

Advantages of using a WDM.

  • The digital signals that are set can always be mixed as well as matched
  • Enhancements are expected to be done to the channels 80-128
  • Given that the wavelengths can be gotten from a normal link, the current equipment in the market can be made use of.


There are only two types of WDMs

(DWDM) Dense Wavelength Division Multiplexer

  • These use analog techniques to increase the capacity of the fiber networks beyond the normal levels that can be acquired by time division Multiplexing.
  • Different wavelengths can carry different streams of information in one fiber cable with very little interference.
  • Many systems meant to cover long distances can give between 16 and 40 wavelengths all at speeds of 2.5Gbps

(CWDM) Course Wavelengths Division Multiplexer

  • They increase the spacing during channeling allowing fewer sophisticated and as a result cheaper designs of transceivers.
  • To give about 8 channels on one fiber cable, the CWDM makes use of the entire bandwidth between the third and the second window.


These include:-

  • Cable type
  • Range of the wavelength
  • Bandwidth
  • Channel spacing
  • Number of the channels
  • Insertion loss
  • Isolation
  • Polarization dependent loss
  • Connectors of WDM

These include:-

  • FC and D4 – they are very durable
  • MU
  • Bionic connectors that have tapered ends for very low insertion loss


  • These multiplexers can be used in cables for submarines to reduce the cost as well as increase their life span.