DENSE WAVELENGTH DIVISION MULTIPLEXING
INTRODUCTION
There has always been a technological talent to fulfill the constant need to extent the capacity of communication channel and DWDM (Dense Wavelength Division Multiplexing) has dramatically brought about an explosive enlargement of the capacity of fiber network, solving the problem of increasing traffic demand most economically.
DWDM is a technique that makes possible transmission of multiple discrete wavelengths carrying data rate as high as fiber plant allows over a single fiber unidirectionally or bidirectionally.
It is an advanced type of WDM in which the optical channels are more closely spaced than WDM.
PRINCIPLE OF DWDM TECHNOLOGY
In normal optical link there is one optical source at transmitting end and one photo detector at receiving end. Signals from different light sources use separate and unique assigned fiber for transmission of signal. As the spectral bandwidth of the laser source is very narrow, this type of transmission makes use of only a small portion of the entire optical band and remaining portion of the band is not used. In DWDM technology, the different light sources are first converted to pre-assigned wavelength according to the DWDM standards and then combined in such a manner that they occupy different portion of the available optical band. In between the two optical signals suitable guard band is also left, so that there is no interference from adjacent channels. Thus DWDM technology makes use of the entire optical bandwidth.
