Intensity modulation

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In

signal
. The envelope of the modulated optical signal is an analog of the modulating signal in the sense that the instantaneous power of the envelope is an analog of the characteristic of interest in the modulating signal.

The recovery of the modulating signal is typically achieved by direct detection, not

homodyne systems are of interest because they are expected to produce an increase in sensitivity of up to 20 dB[2] allowing longer hops between islands for instance. Such systems also have the important advantage of very narrow channel spacing in optical frequency-division multiplexing (OFDM) systems.[3] OFDM is a step beyond wavelength-division multiplexing (WDM). Normal WDM using direct detection does not achieve anything like the close channel spacing of radio frequency FDM.[4]

Intensity modulation with direct detection

Intensity Modulation / Direct Detection (IM/DD) is a scheme is simple and cost-effective in fiber optic communication, making it a suitable for various optical communication applications. It involves modulating the optical power of the carrier signal to represent the transmitted data. This modulation can be achieved using techniques, such as

Fabry-Perot or distributed feedback (DFB).[5]

At the receiver end, direct detection (DD) is used to recover the modulated signal. The modulated optical signal is detected by a

PIN or APD photodiode), which converts the optical power variations into corresponding electrical current or voltage variations. The output of the photodetector is then processed and decoded to retrieve the original information.[5]

See also

References

  1. ISBN 9027726779
    .
  2. ISBN 8122404693
    .
  3. ISBN 8122404693
    .
  4. ISBN 0070445567
    .
  5. ^
    ISSN 0018-9480
    .

Public Domain This article incorporates public domain material from Federal Standard 1037C. General Services Administration. Archived from the original on 2022-01-22. (in support of MIL-STD-188).

Further reading

  • William Shieh, Ivan Djordjevic, OFDM for Optical Communications, Academic Press, 2009
    ISBN 0-12-374879-8
    .
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