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.
The recovery of the modulating signal is typically achieved by direct detection, not heterodyning. However, optical heterodyne detection is possible and has been actively studied since 1979. Bell Laboratories had a working, but impractical, system in 1969.[1] Heterodyne and 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]
^T. G. Hodgkinson, D. W. Smith, R. Wyatt, D. J. Malyon, "Coherent optical fibre transmission systems", in Bishnu P Pal (ed), Fundamentals Of Fibre Optics In Telecommunication And Sensor Systems ,page 470, Bohem Press, 1992 ISBN 8122404693.
^Chinlon Lin, "Opto-electronics and the information age: a perspective", in Bishnu P Pal (ed), Fundamentals Of Fibre Optics In Telecommunication And Sensor Systems ,page 20, Bohem Press, 1992 ISBN 8122404693.
^Ananth Selvarajan, Subrat Kar, T. Srinivas. Optical Fiber Communication: Principles and Systems, page 129, Tata McGraw-Hill Education, 2003 ISBN 0070445567.
and 21 Related for: Intensity modulation information
In optical communications, intensitymodulation (IM) is a form of modulation in which the optical power output of a source is varied in accordance with...
that for data transmission uses visible light, and does not use intensitymodulation of optical sources. The idea is to use vibration generator instead...
competition among several lasing modes. Intensitymodulation of SLEDs can be easily achieved through direct modulation of the bias current. SLED modules do...
light modulation at relatively low frequencies (< 80 Hz) and small intensitymodulation levels. Stroboscopic effect may become visible for a person when...
of Schumann resonances in California and Australia – Evidence for intensitymodulation by the local height of the D region". Journal of Geophysical Research...
create IMRT distributions (MLCs really provide a fluence modulation rather than intensitymodulation). The MLC is an important tool for radiation therapy...
(KPR) Modulation transfer function MTF (modulation transfer function is the ratio of image intensitymodulation and object intensitymodulation and it...
approximation for a light emitting diode (LED). The corresponding intensitymodulation is shown to be substantial only in the neighborhood of position z0...
simply the next item in the optical transmission chain. A variant, the modulation transfer function (MTF), neglects phase effects, but is equivalent to...
frequency of the modulation; the amplitude or depth of the modulation (i.e., what is the maximum percent decrease in the illumination intensity from its peak...
tissue being irradiated in the treatment field. In some systems, this intensitymodulation is achieved by moving the leaves in the MLC during the course of...
signal encoding is typically simple intensitymodulation, although historically optical phase and frequency modulation have been demonstrated in the lab...
result of the change in refractive index in the active region during intensitymodulation. It is possible to evaluate the shift in wavelength by determining...
based on new materials, showing that not only gliding tones but also intensitymodulation plays a role in distinguishing Silbo's sounds. Trujillo's 2005 collaboration...
; Suzuki, S.; Asada, M.; Nishiyama, N.; Arai, S. (2012). "Direct intensitymodulation and wireless data transmission characteristics of terahertz-oscillating...
obtain modulation of intensity of a light beam, is to modulate the current driving the light source, e.g. a laser diode. This sort of modulation is called...
fluctuations in intensity; in lasers with many thousands of modes, these interference effects tend to average to a near-constant output intensity. If instead...
optical properties near the absorption edge, which are useful for intensitymodulation and optical switching. Namely, in a mathematical point of view, if...
stream cipher by the Yuen 2000 protocol: Design and experiment by an intensity-modulation scheme". Physical Review A. 72 (2): 022335. arXiv:quant-ph/0507043...
In the fields of nonlinear optics and fluid dynamics, modulational instability or sideband instability is a phenomenon whereby deviations from a periodic...
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