Intensity modulation
In optical communications, intensity modulation (IM) is a form of modulation in which the optical power output of a source is varied in accordance with some characteristic of the modulating 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. Recovery of the modulating signal is by direct detection, not heterodyning.
References
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).
Intensity modulation is the process of modulating the laser source directly by the analogue modulating signal. The intensity of the optical signal is varied in accordance with the amplitude of the modulating signal. The receiver consists of a photo detector to convert the optical signal to electrical form which is then passed through a low pass filter to get the modulating signal.
Further reading
- William Shieh, Ivan Djordjevic, OFDM for Optical Communications, Academic Press, 2009 ISBN 0-12-374879-8.