Continued… DWDM Part II

Continue from last post on DWDM history, the figure below shows the evolution or progression of the WDM technology that can be seen as an increase in the number of wavelengths accompanied by a decrease in the spacing of the wavelengths. Along with increased density of wavelengths, systems also advanced in their flexibility of configuration, through add-drop functions, and management capabilities.

Evolution of DWDM

Evolution of DWDM

  • Early WDM began in the late 1980’s using the two widely spaced wavelengths in the 1310 nm and 1550 nm (or 850 nm and 1310 nm) regions, sometimes called wideband WDM.
  • The early 1990’s saw a second generation of WDM, sometimes called narrowband WDM, in which two to eight channels were used. These channels were now spaced at an interval of about 400 GHz in the 1550-nm window.
  • By the mid-1990’s, dense WDM (DWDM) systems were emerging with 16 to 40 channels and spacing from 100 to 200 GHz.
  • By the late 1990’s DWDM systems had evolved to the point where they were capable of 64 to 160 parallel channels, densely packed at 50 or even 25 GHz intervals.

Increases in channel density resulting from DWDM technology have had a dramatic impact on the carrying capacity of fiber. In 1995, when the first 10 Gbps systems were demonstrated, the rate of increase in capacity went from a linear multiple of four every four years to four every year as shown in figure below.

Growth In Fiber Capacity

Growth In Fiber Capacity

Source:   Introduction to DWDM for Metropolitan Networks

To be continued… DWDM Part III

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