13 March 2018

What is WDM

In this method, the scheme of combining a number of wavelength over a single fiber called wavelength division multiplexing. In this techniques fiber optic transmission using multiple light wavelength to send the data over the same medium or device. In fiber optic, two or more wavelength (colors) of light can travel on one fiber and several signals can be transmitted in optical waveguide at differing wavelengths. 

So the combining a number of wavelengths over a single fiber called WDM full form is wavelength division multiplexing.

In WDM each input generated by a separate optical source with a unique wavelength. An optical multiplexer couples light from individual sources to the transmitting fiber shown in the figure. 

At the receiving station, an optical demultiplexer is required to separate the different carriers before photodetection of the individual signal.

WDM scheme
To prevent spurious signal to enter into receiving channel, the demultiplexer must have a narrow spectral operation with sharp wavelength cut-offs. The acceptable limit of cross talk is -30 dB. 

Features of WDM :

The following features of WDM are given below:
  • Capacity upgrade for the system - Each wavelength support independent data rate in Gbps.
  • Wavelength routing for the device - Link capacity and flexibility can be increased by using multiple wavelengths.
  • Transparency of the system - WDM can carry fast asynchronous, slow synchronous, synchronous analog and digital data.
  • Wavelength switching for the system - WDM can add or drop multiplexer, cross-connects and wavelength converters.
WDM has wide application in the communication system because of this useful feature details we show above. Other method called DWDM, it's different from WDM. The main difference between WDM and DWDM is DWDM has a greater overall capacity so DWDM spaces the wavelength more closely than WDM.

Application of WDM :
  • SONET network
  • Dense WDM allows to muxed and de-muxed numbers of channel closer to one another to achieve greater efficiency
  • FDM to an optical fiber
  • Optical transport network
  • Local exchange network
WDM driver:

WDM driver is classified into three types :
  • Bus driver
  • Function driver
  • Filter driver
Function driver :
  • A function driver is a specific individual device, such as a printer.
Bus driver :
  • Bus driver uses individual buses like PCI, SCSI, and USB, adapter or bridges. It is reported to the child device that is connected to the bus.
Filter driver :
  •  It is I/O request for a device, which is a class of device or bus device.