Measurements of 0.63mm Laser-beam Scintillation in Strong Atmospheric Turbulence
Measurements of 0.63mm Laser-beam Scintillation in Strong Atmospheric Turbulence

Author: G. R. Ochs

Publisher:

Published: 1969

Total Pages: 28

ISBN-13:

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Log-amplitude variance and covariance of the scintillation of a diverging optical beam have been measured over a 48-hr period at a wavelength of 0.63[mu], on a 490 and 1000 m optical paths 2 m above the surface of a flat mesa near Boulder, Colorado. Simultaneous measurements of the refractive-index structure of the atmosphere have been obtained from temperature-structure-function measurements at spacings of 1, 3, and 10 cm. A saturation of scintillation occurs for values of log-amplitude variance between 0.5 and 1. After reaching a peak, the log-amplitude variance then decreases with both increasing range and increasing refractive-index turbulence. The spatial covariance of the fluctuations tends to increase in the saturation region. In the unsaturated region, the log-amplitude variance is approximately that predicted by the spherical-wave propagation theory of Tatarski.

Laser Beam Scintillation with Applications
Laser Beam Scintillation with Applications

Author: Larry C. Andrews

Publisher: SPIE Press

Published: 2001

Total Pages: 408

ISBN-13: 9780819441034

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Renewed interest in laser communication systems has sparked development of useful new analytic models. This book discusses optical scintillation and its impact on system performance in free-space optical communication and laser radar applications, with a detailed look at propagation phenomena and the role of scintillation on system behavior. Intended for practicing engineers, scientists, and students.

Airborne Laser Beam Propagation Measurements of High-Altitude Atmospheric Turbulence
Airborne Laser Beam Propagation Measurements of High-Altitude Atmospheric Turbulence

Author: Glen J. Morris

Publisher:

Published: 1972

Total Pages: 62

ISBN-13:

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Two NC-135 jet aircraft were used in an airborne laser beam scintillation experiment in order to measure high-altitude values of the index of refraction structure. Measurements were made for transmitter-receiver spacings of 0.5, 1.5, 2.0, and 3.0 km. Altitude values ranged from 1.5 km to 10.5 km in approximately 1.5 km increments. Measurements were made at optical wavelengths of 0.6328 micrometers and 10.6 micrometers. Computed scintillation parameters include log-intensity variance, probability distribution function, cumulative probability, and temporal power spectral density. Measured values of index of refraction structure were consistently higher than expected at high altitudes. Some contributions to the measured values of index of refraction structure may have come from boundary layer turbulence near the transmitting aircraft. However, this contribution is small. On the average, the upper atmosphere is much more turbulent than current models predict it to be.

Experimental Investigations of Optical Propagation in Atmospheric Turbulence
Experimental Investigations of Optical Propagation in Atmospheric Turbulence

Author: Michael W. Fitzmaurice

Publisher:

Published: 1971

Total Pages: 196

ISBN-13:

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The pertinent theoretical background and the results of a group of experiments conducted over 0.4- and 1.17-km near-ground horizontal ranges are presented. (1) The log-amplitude variances for HeNe (0.633 μm) and CO2 (10.6 μm) laser beams were found to have a ratio of 26.8, which is in close agreement with the predictions of Rytov-based spherical-wave theory. (2) Published measurements of the saturation level of the log-amplitude variance are reviewed and several inconsistencies noted. (3) The spatial correlation function of irradiance field was measured and found to agree with theory. The degree of correlation between different frequency beams which had traversed the same optical path was also measured and compared to theory. The data exhibited an unacceptably large scatter and did not show the wavelength dependence. (4) The log-normal, Rayleigh, and Rice probability distributions are discussed in terms of their applicability to irradiance statistics. Relatively weak 10.6 μm irradiance fluctuations were found to be equally well described by the log-normal and Rice distributions; strong fluctuations obtained at 0.488 μm were clearly best described by the log-normal distribution.