Moustafa Hussein Aly
Free-Space Optical Communications in Turbulent Channels
The atmospheric turbulence effect on free-space optical (FSO)
communications is one of the biggest problems that face FSO systems.
Atmospheric turbulence is the fluctuations of the signal due to the
changing of refractive index which results from those air particles which
are not homogonous and are affected by temperature, pressure, altitude
and wind. In this book, different proposed modulation and forward error
techniques are applied to decrease the severe effect on bit error rates due
to atmospheric turbulence.
Two channels models of atmospheric turbulence are used: log-normal
channel which represents small distances (i.e. less than 100 m) and
negative-exponential channel which represents long distances up to
several kilometers. The obtained results demonstrated the superior
performance of avalanche photodiode over positive-intrinsic-negative
(PIN) receivers with the use of concatenated Reed Solomon codes.
Further, it is found that, forward error correction upgrades uncoded FSO
to gain a working-distance advantage of a few kilometers.|