Wavelength division multiplexing (WDM)

Wavelength division multiplexing (WDM):


Wavelength division multiplexing (WDM)
Wavelength division multiplexing (WDM)
Wavelength-division multiplexing (WDM) could be a technique of mixing multiple signals on optical device beams at varied infrared (IR) wavelengths for transmission on fiber optic media. every optical device is modulated by AN freelance set of signals. Wavelength-sensitive filters, the IR analog of visible-light color filters, square measure used at the receiving finish.

WDM is analogous to frequency-division multiplexing (FDM). however rather than going down at radio frequencies (RF), WDM is completed within the IR portion of the spectrumevery IR channel carries many RF signals combined by suggests that of FDM or time-division multiplexing (TDM). every multiplexed IR channel is separated, or demultiplexed, into the initial signals at the destination. victimization FDM or TDM in every IR channel together with WDM or many IR channels, information completely different|in several|in numerous} formats and at different speeds will be transmitted at the same time on one fiber.

Wavelength division multiplexing (WDM)
Wavelength division multiplexing (WDM)

 

In early WDM systems, there have been 2 IR channels per fiber. At the destination, the IR channels were demultiplexed by a dichroic (two-wavelength) filter with a cutoff wavelength some midway between the wavelengths of the 2 channels. It before long became clear that quite 2 multiplexed IR channels might be demultiplexed victimization cascaded dichroic filters, giving rise to coarse wavelength-division multiplexing (CWDM) and dense wavelength-division multiplexing (DWDM). In CWDM, there square measure sometimes eight completely different IR channels, however there will be up to eighteen. In DWDM, there will be dozens. as a result of every IR channel carries its own set of multiplexed RF signals, it's on paper potential to transmit combined information on one fiber at a complete effective speed of many hundred gigabits per second (Gbps).

The use of WDM will multiply the effective information measure of a fiber optic communications system by an outsized issuehowever its value should be weighed against the choice of victimization multiple fibers bundled into a cable. A fiber optic repeater device known as the Er electronic equipment will build WDM a cheap long-run answer



working of Wavelength division multiplexing (WDM)

Wavelength division multiplexing (WDM)
Wavelength division multiplexing (WDM)

Q. what one can do with wavelength division multiplexing ?

Answer:

            Using wavelength division multiplexing (WDM) technology several wavelengths, or light colors, can simultaneously multiplex signals of 2.5 to 40 Gbps each over a strand of fiber. Without having to lay new fiber, the effective capacity of existing fiber plant can routinely be increased by a factor of 16 or 32. Systems with 128 and 160 wavelengths are in operation today, with higher density on the horizon. The specific limits of this technology are not yet known.

WDM increases the carrying capacity of the physical medium (fiber) using a completely different method from TDM. WDM assigns incoming optical signals to specific frequencies of light (wavelengths, or lambdas) within a certain frequency band. This multiplexing closely resembles the way radio stations broadcast on different wavelengths without interfering with each other (see Figure 1-7). Because each channel is transmitted at a different frequency, we can select from them using a tuner. Another way to think about WDM is that each channel is a different color of light; several channels then make up a “rainbow.”