Dense wavelength division multiplexing (DWDM) is a technology that puts data from different sources together on an optical fiber, with each signal carried at the same time on its own separate light wavelength. Using DWDM, up to 80 (and theoretically more) separate wavelengths or channels of data can be multiplexed into a lightstream transmitted on a single optical fiber.

Each channel carries a wave division multiplexed (WDM) signal. WDM is a method of combining multiple signals on laser beams at various infared (IR) wavelengths for transmission along fiber optic media. In a system with each channel carrying 2.5 Gbps (billion bits per second), up to 200 billion bits can be delivered a second by the optical fiber.

Working

DWDM system is composed of five components. Working is explained below:-

1. The transponder accepts input in the form of a standard single-mode or multimode laser pulse. The input can come from different physical media and different protocols and traffic types.

2.The wavelength of the transponder input signal is mapped to a DWDM wavelength.

3.DWDM wavelengths from the transponder are multiplexed with signals from the direct interface to form a composite optical signal which is launched into the fiber.

4.A post-amplifier (booster amplifier) boosts the strength of the optical signal as it leaves the multiplexer.

5.An OADM is used at a remote location to drop and add bitstreams of a specific wavelength.

6.Additional optical amplifiers can be used along the fiber span (in-line amplifier) as needed.

7.A pre-amplifier boosts the signal before it enters the d e muliplexer.

8.The incoming signal is demultiplexed into individual DWDM wavelengths.

9.The individual DWDM lambdas are either mapped to the required output type through the transponder or they are passed directly to client-side equipment.

ADVANTAGES

1.Less fiber cores to transmite and receive high capacity data

2.A single core fiber cable could divided into multiple channels instead of using 12 fiber core.

3.Easy network expansion, especially for limited fiber resource, no need extra fiber but add wavelength, Low cost for expansion, because no need to replace many components such as optical amplifiers, Can move to STM-64 when economics improve

4.DWDM systems capable of longer span lengths, TDM approach using STM-64 is more costly and more susceptible to chromatic and polarization mode dispersion