Editing Frequency-division multiplexing (section)

{{Short description|Signal processing technique in telecommunications}}
{{Use American English|date = March 2019}}
{{refimprove|date=February 2008}}
{{Multiplex techniques}}
In [[telecommunications]], '''frequency-division multiplexing''' ('''FDM''') is a technique by which the total [[bandwidth (signal processing)|bandwidth]] available in a [[communication channel|communication medium]] is divided into a series of non-overlapping [[frequency bands]], each of which is used to carry a separate signal. This allows a single transmission medium such as a microwave radio link, cable or [[optical fiber]] to be shared by multiple independent signals. Another use is to carry separate serial bits or segments of a higher rate signal in [[Parallel communication|parallel]].
 
The most common example of frequency-division multiplexing is [[radio]] and television broadcasting, in which multiple radio signals at different frequencies pass through the air at the same time.  Another example is [[cable television]], in which many television channels are carried simultaneously on a single cable. FDM is also used by telephone systems to transmit multiple telephone calls through high capacity trunklines, [[communications satellite]]s to transmit multiple channels of data on uplink and downlink radio beams, and broadband [[DSL modem]]s to transmit large amounts of computer data through [[twisted pair]] telephone lines, among many other uses.

An analogous technique called [[wavelength division multiplexing]] is used in [[fiber-optic communication]], in which multiple channels of data are transmitted over a single [[optical fiber]] using different [[wavelength]]s (frequencies).