wavelength division multiplexing

communications (WDM) Multiplexing several Optical Carriern signals on a single optical fibre by using different

wavelengths (colours) of laser light to carry different

signals.

The device that joins the signals together is known as a

multiplexor, and the one that splits them apart is a

demultiplexor. With the right type of fibre you can have a

device that does both and that ought to be called a "mudem"

but isn't.

The first WDM systems combined two signals and appeared around

1985. Modern systems can handle up to 128 signals and can

expand a basic 9.6 Gbps fibre system to a capacity of over

1000 Gbps.

WDM systems are popular with telecommunications companies

because they allow them to expand the capacity of their fibre

networks without digging up the road again. All they have to

do is to upgrade the (de)multiplexors at each end. However

these systems are expensive and complicated to run. There is

currently no standard, which makes it awkward to integrate

with older but more standard SONET systems.

Note that this term applies to an optical carrier (which is

typically described by its wavelength), whereas frequencydivision multiplexing typically applies to a radio carrier

(which is more often described by frequency). However, since

wavelength and frequency are inversely proportional, and since

radio and light are both forms of electromagnetic radiation,

the distinction is somewhat arbitrary.

See also time division multiplexing, code divisionmultiplexing.

[Is "wave division multiplexing", as in "dense wave division

multiplexing" (DWDM) just a trendy abbreviation?]

(2002-07-16)