The Optical Scatter Channel and Its Properties

  • Sherman Karp
  • Robert M. Gagliardi
  • Steven E. Moran
  • Larry B. Stotts
Part of the Applications of Communications Theory book series (ACTH)


With the introduction of ultraviolet, visible, and infrared technologies in the areas of communications and surveillance, it has become necessary to account for the atmospheric and oceanic influences on such systems—in specific terms, the effects of particulate multiple scattering on optical radiation transfer. This is because the haze, fog, rain, and clouds comprising most of the atmospheric channel, and the yellow substance and small “sea animals” in the marine channel, cause the majority of the degradation suffered by the information-containing signal traversing that channel. Recall from the previous chapter that atmospheric and marine turbulence can generate significant wavefront distortions of a signal when optical paths of 50 meters or more are involved. However, the total angular and spatial spreading which can be experienced by an initially collimated pencil beam rarely exceeds 100 microradians and a meter or two, respectively.(1) Also, coherence distances are still on the order of centimeters (requiring only modest diversity of a coherent receiver), and no experimental evidence of pulse broadening exists, even down to picosecond lengths.(2,3) In contrast, particulate multiple scatter can induce dispersion in angle of arrival the order of tens of degrees, beam spreading in the hundreds of meters, degradation of spatial coherence down to lengths of microns or less, and multipath time spreading in the tens of microseconds.(4) Because of the magnitude of these larger effects, the mutual coherence function approach to channel characterization cannot be universally applied (we will shortly find it to be valid only over a finite range of scattering thicknesses), and additional mathematical techniques must be used to model optical propagation through these individual channels. In this chapter, we shall review the inherent and characterizing properties of the three basic components of the optical scatter channel: the atmosphere, the ocean, and the air/sea interface. A clear understanding of these building blocks must be possessed if one is to model satisfactorily the transfer of optical radiation through their individual and/or combined parts. Chapter 7 will describe how this information has been, and is currently, used to quantify energy propagation through the invididual and combined structures of this channel. Whenever possible, we have compared measured characteristics of the channel and its components with predictions from pertinent analytical or empirically devised models.


Attenuation Coefficient Secchi Depth Inherent Property Cloud Type Extinction Efficiency 
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Copyright information

© Springer Science+Business Media New York 1988

Authors and Affiliations

  • Sherman Karp
    • 1
  • Robert M. Gagliardi
    • 2
  • Steven E. Moran
    • 3
  • Larry B. Stotts
    • 4
  1. 1.Lutronix, Inc.San DiegoUSA
  2. 2.University of Southern CaliforniaLos AngelesUSA
  3. 3.SAICSan DiegoUSA
  4. 4.DARPAArlingtonUSA

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