Votes: 0Posted On: Nov 13, 2017 08:13:19
Before diving into the CWDM and DWDM comparison, let us first understand the concept of WDM(Wavelength-Division Multiplexing). WDM is a technology used to transmit optical signals in an optical fiber cable. Optical fibers use light rays as a medium to transmit signals.
With the help of WDM, you can transmit multiple optical signals in a single optical cable. This is done by transmitting optical signals at different wavelengths. This is achieved with the help of multiplexer which is used to couple all the signals at the time of transmitting and separate them at the receiving end.
Broadly speaking, there are two types of WDM systems that used most widely, the CWDM(Coarse Wavelength-Division Multiplexing) and DWDM(Dense Wavelength-Division Multiplexing). Here are some of the key factors that separate the two.
Number of Wavelengths
On a basic level, CWDM and DWDM differ on the number of wavelengths they can transmit over the medium. CWDM can transmit up to 18 wavelength channels through a single optical fiber at the same time. However, DWDM can support about 80 wavelength channels through a single optical fiber simultaneously.
As there are fewer wavelengths per fiber in the CWDM, the space between each wavelength is more than DWDM. CWDM supports about 20nm of spacing between wavelengths. Whereas, DWDM supports about 0.8nm of spacing.
CWDM is very effective in transmitting signals up to 70 kms. However, beyond 40 kms the number of wavelengths have to be reduced for efficient transmission. For transmission over long distances, DWDM can be used for efficient transmission.
Cost vs Capacity
While choosing your mode of transmission, you have to keep the cost vs capacity constraint in mind. While CWDM is cheaper, it offers less capacity. Whereas, DWDM offers more capacity and is costlier than CWDM.