Wavelength Division Multiplexing (WDM)

WDM is one of the implementation of #Multiplexing, classified as #Frequency Division Multiplexing (FDM), which utilises the feature of the light as a wave. Since light waves of different wavelengths do not interfere with one another within a medium, it is possible to multiplex different channel travelling in different wavelengths in a single Fibre-Optic Cable simultaneously.

There are several technologies utilise WDM as a mean for multiplexing especailly those that are travelling with optical light pulses:

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Multiplexing

Wavelength Division Multiplexing (WDM)#
Frequency Division Multiplexing (FDM)

Wavelength Division Multiplexing (WDM)#
Dense Wavelength Division Multiplexing (DWDM)

DWDM uses the same #multiplexing technique as Coarse Wavelength Division Multiplexing (CWDM). However, compare to CWDM ability to multiplex 8 signals, DWDM system is able to multiplex 32 signals into a single fibre. Additionally, the signals can be amplified, making them keen to be transmitted up to 250 km. The conversion between electrical signals and light are done by Fibre-Optic Transmission Systems (FOTS), which is a Modulator.
Coarse Wavelength Division Multiplexing (CWDM)

CWDM uses wavelength-specific pairs of Gigabit Interface Converters (GBIC) connected to a Switch# pair in order to #multiplex up to 8 #Fibre-Optic Cable signals onto a single fibre. Each GBIC pair is tuned to a specific frequency that allows the switch to add (mux) or pluck out (demux) a single beam of light (data stream). However, CWDM is unable to be amplified, which limited its maximum distance to 80 km for point-to-point or a ring circumference of 30 km.

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