Basics of Multiplexing and WDM

Multiplexing

Multiplexing is a technique used to combine and transmit the multiple data streams over a single medium. The process of combining the data streams is known as multiplexing and hardware used for multiplexing is known as a multiplexer.

Multiplexing is accomplished by using a device called Multiplexer (MUX) that combines an input lines to generate a single output line. It follows many to one approach.

De-multiplexing is achieved by using a device called De-multiplexer (DEMUX) available at the receiving end. DEMUX separates a signal into its component signals (one input and n outputs). Therefore, we can say that de-multiplexing follows the one-to-many approach.

Advantage:

• More than one signal can be sent over a single medium.
• The bandwidth of a medium can be utilized efficiently.

There are mainly two types of multiplexers, namely analog and digital. They are further divided as below;

• Frequency Division Multiplexing (FDM)
• Wavelength Division Multiplexing (WDM)
• Time Division Multiplexing (TDM)

Wavelength division multiplexing

Wavelength Division Multiplexing (WDM) is a fibre optical communication technique that enables the use of multiple light wavelengths or multiple colours of light to send data/traffic over the same medium. There are two types of WDM

• DWDM (Dense WDM)
• CWDM (Coarse WDM)

Coarse WDM (CWDM):  CWDM is defined by WDM systems with fewer than eight active wavelengths per fibre. CWDM is used at short range communications. CWDM is a compact and cost-effective option.

Dense WDM (DWDM): DWDM is defined in terms of frequencies. It is for systems with more than eight active wavelengths per fibre. 

-DR