The Wavelength Division Multiplexing (WDM) is done only in fiber optic channels. In WDM, several light waves from multiple sources are connected by using a prism to form a composite light signal sent across the medium.
At the receiver end, the hybrid light is broken down into different light waves, and these are delivered to their corresponding receiver, as shown in the figure below. The concept of WDM and Frequency-Division Multiplexing (FDM) is the same.
The application of WDM is the Synchronous Optical Network (SONET) in which various optical fiber lines are multiplexed and demultiplexed. There is a new technique known as DWDM (dense WDDM). It can take multiple huge computers of the medium by composing a medium closer to one another. It achieves even greater efficiency.
The two types of Wavelength Division Multiplexing (WDM) are as follows −
Dense Wavelength Division Multiplexing (DWDM)
It is a technology in which many optical signals (laser light) of several wavelengths or colors are grouped into one signal and are sent over the connecting channel to an extended area.
When the optical signal transmission distance turns into thousands of kilometres. Then, few signal losses will appear. To satisfy this signal loss, optical fiber amplifiers are used in the DWDM transmission system.
The DWDM technology needs this gain bandwidth to send various optical signals together effectively. DWDM can send up to 80 channels (80 optical signals) with 100 GHz (0.8 nm) spacing.
Coarse Wavelength Division Multiplexing (CWDM)
CWDM is a technology in which various optical signals (laser light) of multiple wavelengths or colors are grouped into one signal and are sent over the transmission medium for a brief interval.
DWDM technology is usually helpful for long-distance transmission greater than 100 km. But, if the transmission distance is less than 100 kilometres, we are no longer required to facilitate the optical amplifiers.
CWDM system has a medium spacing of 20 nm between the optical signals. This enables the facilitation of low-cost elements, including uncooled lasers, multiplexer (MUX) and demultiplexer (DEMUX).