My apology for being “off mode” for 2 weeks since my last post on July 22. Last week Fri-Sun, my colleagues and I attended our company’s corporate team building event at Jeram Besu, Pahang (Malaysia). It was an enjoyable event with the main activities of white water rafting and 4WD off-road to Jerembun waterfall (not forget to mention that we indulged ourselves with eating durian, king of fruits).

I was also quite busy lately as I was on DWDM assignment. I take this opportunity to explore DWDM and would like to share the info on this blog. This new topic and other future topics on interesting technology or solution will be posted under the new category of “Next Generation Network (NGN)“.

What on earth is DWDM?

DWDM is a short or an acronym for Dense Wavelength Division Multiplexing. DWDM is a fiber-optic transmission technique. It involves the process of multiplexing many different wavelength signals onto a single fiber. So each fiber have a set of parallel optical channels each using slightly different light wavelengths. It employs light wavelengths to transmit data parallel-by-bit or serial-by-character.

In short, DWDM is a technology that uses fiber-optics transmission techniques that employ light wavelengths to transmit data as shown below.
How DWDM works

How DWDM works

Figure above shows a diagram that depicts how DWDM works.  As shown, four incoming sources are:
1. Multiplexed onto one single fiber
2. Transmitted
3. Demultiplexed onto four outgoing fibers (incoming signals are retrieved)

What so special about DWDM?

DWDM is a very crucial component of optical networks that will allow the transmission of data: voice, video-IP, ATM and SONET/SDH respectively, over the optical layer.

This allows service providers to offer the following Triple Play services as IP data over ATM or voice over SONET (or SDH):

  • Video
  • Multimedia
  • E-mail
Development of DWDM Technology
Let’s backtrack a little bit to explore the history of Wavelength Division Multiplexing (WDM) development. Early WDM began in the late 1980s using the two widely spaced wavelengths in the 1310 nm and 1550 nm (or 850 nm and 1310 nm) regions, sometimes called wideband WDM. Figure below shows an example of this simple form of WDM. Notice that one of the fiber pair is used to transmit and one is used to receive. This is the most efficient arrangement and the one most found in DWDM systems.
Example of simple form of WDM with 2 channels

Example of simple form of WDM with 2 channels


  • DWDM: Dense Wavelength Division Multiplexing
  • WDM: Wavelength Division Multiplexing
  • NGN: Next Generation Network
  • ATM: Asynchronous transfer mode
  • SONET: Synchronous data transmission on optical media (American National Standards)
  • SDH: Synchronous Digital Hierarchy (international equivalent of SONET)
  • IP: Internet Protocol

Dense Wavelength Division Multiplexing (DWDM) by Luc Pelletier & Miguel Pinard
Introduction to DWDM for Metropolitan Networks

To be continued… DWDM Part II


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