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a multiplexing technique working in the wavelength domain An analog multiplexing technique to combine optical signal.
The concept was first published in 1970, and by 1978 WDM systems were being realized in the laboratory. The first WDM systems only combined two signals. Modern systems can handle up to 160 signals and can thus expand a basic 10 Gbit/s fiber system to a theoretical total capacity of over 1.6 Tbit/s over a single fiber pair.
In fiber-optic communications Wavelength –division multiplexing (WDM) is a technology which multiplexes multiple optical carrier signals on a single optical fiber by using different (colours) of laser light to carry different signals.
With the exponential growth in communications, caused mainly by the wide acceptance of the Internet, many carriers are finding that their estimates of fiber needs have been highly underestimated. Although most cables includedmany spare fibers when installed, this growth has used many of them and new capacity is needed.
1)installing more cables,2) increasing system bit rate to multiplex more signals3) wavelength division multiplexing.
DWDM No official or standard definition Implies more channels more closely spaced that WDM DWDM-based networks create a lower cost way to quickly respond to customers bandwidth demands and protocol changes. A key advantage to DWDM is that its protocol- and bit-rate independent.
CWDM No official or standard definition number of channals is fewer than in dense wavelength division multiplexing (DWDM) but more than in standard wavelength division multiplexing (WDM). Laser emmission
CWDM system have channel at wavelengths spaced 20 nanometers (nm). DWDM 0.4 nm spacing Energy tolerance
• WDM technology allows multiple connections over one fiber thus reducing fiber plant requirement. – This is mainly beneficial for long-haul applications. – Campus applications require a cost benefit analysis.• WDM technology can also provide fiber redundancy.• WDM provides a managed fiber service.