资料来源 : Free On-Line Dictionary of Computing

frequency division multiplexing
     
         (FDM) The simultaneous transmission of
        multiple separate signals through a shared medium (such as a
        wire, {optical fibre}, or light beam) by modulating, at the
        transmitter, the separate signals into separable frequency
        bands, and adding those results linearly either before
        transmission or within the medium.  While thus combined, all
        the signals may be amplified, conducted, translated in
        frequency and routed toward a destination as a single signal,
        resulting in economies which are the motivation for
        multiplexing.  Apparatus at the receiver separates the
        multiplexed signals by means of frequency passing or rejecting
        filters, and demodulates the results individually, each in the
        manner appropriate for the modulation scheme used for that
        band or group.
     
        Bands are joined to form groups, and groups may then be joined
        into larger groups; this process may be considered
        recursively, but such technique is common only in large and
        sophisticated systems and is not a necessary part of FDM.
     
        Neither the transmitters nor the receivers need be close to
        each other; ordinary radio, television, and cable service are
        examples of FDM.  It was once the mainstay of the long
        distance telephone system.  The more recently developed {time
        division multiplexing} in its several forms lends itself to
        the handling of digital data, but the low cost and high
        quality of available FDM equipment, especially that intended
        for television signals, make it a reasonable choice for many
        purposes.
     
        Compare {wavelength division multiplexing}, {time division
        multiplexing}, {code division multiplexing}.
     
        (2001-06-28)