Dense Wavelength Division Multiplexing (DWDM)


Definition of DWDM – Dense Wavelength Division Multiplexing in Network Encyclopedia.

What is DWDM (Dense Wavelength Division multiplexing)?

DWDM is a technology for achieving extremely high data rates over fiber-optic cabling. Also known as wave division multiplexing (WDM), dense wavelength division multiplexing (DWDM) will likely replace time-division multiplexing (TDM) as the standard transmission method for high-speed fiber-optic backbones in the next few years.

DWDM - Dense Wavelength Division multiplexing
DWDM – Dense Wavelength Division multiplexing

How DWDM works?

DWDM modulates multiple data channels into optical signals that have different frequencies and then multiplexes these signals into a single stream of light that is sent over a fiber-optic cable.

Each optical signal has its own frequency, so up to 80 data streams can be transmitted simultaneously over the fiber using only eight different light wavelengths.

In addition, each data stream can employ its own transmission format or protocol. This means that using DWDM, you can combine Synchronous Optical Network (SONET), Asynchronous Transfer Mode (ATM), TCP/IP, and other transmissions and send them simultaneously over a single fiber.

At the other end, a multiplexer demultiplexes the signals and distributes them to their various data channels.

Devices that support DWDM are more costly because the laser light sources for generating signals over fiber must be highly stable.

Alternative to DWDM

Coarse wavelength division multiplexing (CWDM) also uses laser beams to transmit information over fiber optic cables. Because it uses less-sophisticated electronics and photonics, CWDM channels are much wider than DWDM channels, which means it supports fewer channels.

CWDM can be significantly less expensive than DWDM, as well as more tolerant of low-grade fiber, single-fiber strands, and multimode fiber.

DWDM explained in video

As we all have learned from elementary school science, a white light beam can be separated into individual colored light beams by a prism, as shown in this picture. Vice versa, individual colored light beams can also be combined into a single white light beam by the prism, that is if we use the prism in the reverse direction.

WDM uses this same idea. Traditionally, only one colored light was used on a single strand of fiber to carry the information, such as 1550nm light. However, starting from the early 1990s, the Internet boom pushed service providers to find a method to increase the capacity on their network in the most economical way. That is when WDM devices were invented.

Watch the video to learn more »»

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