Preface ........................................................ ix
Acknowledgments .............................................. xiii
About the Authors .............................................. xv
Chapter 1 Atmosphere: Structure and Processes .................. 1
1.1 Vertical Profiles of Temperature, Pressure, and Number
Density .................................................... 1
1.2 Aerosols ................................................... 2
1.2.1 Aerosol Loading ..................................... 4
1.2.2 Aerosol Size Distribution and Spectral Extinction ... 7
1.3 Hydrometeors .............................................. 12
1.3.1 Fog ................................................ 12
1.3.2 Rain ............................................... 13
1.3.3 Clouds ............................................. 13
1.3.3.1 First Cloud Cover Model ................... 14
1.3.3.2 Second Cloud Cover Model .................. 14
1.3.3.3 Third Cloud Cover Model ................... 15
1.3.3.4 Ceiling Cloud Model ....................... 15
1.3.4 Snow ............................................... 15
1.4 Atmospheric Turbulence .................................... 16
1.4.1 Energy Cascade Theory .............................. 16
1.4.2 Spectral Characteristics ........................... 21
1.4.3 C2n Altitude Distribution ........................... 24
1.4.4 L0 Altitude Distribution ........................... 26
1.4.5 Non-Kolmogorov Turbulence .......................... 28
1.4.6 Generalized Power Spectrum ......................... 31
References ..................................................... 33
Chapter 2 Optical Wave Propagation in the Atmosphere .......... 41
2.1 Refraction Phenomena ...................................... 41
2.2 Effects of Aerosols ....................................... 43
2.2.1 Attenuation of Aerosols ............................ 44
2.2.2 Scattering by Aerosols ............................. 45
2.3 Aerosol Effects on Optical Wave Propagation ............... 46
2.3.1 Atmospheric Transmission ........................... 49
2.3.2 Aerosol Beam Widening .............................. 50
2.4 Effects of Hydrometeors ................................... 53
2.4.1 Effects of Clouds and Fog .......................... 53
2.4.2 Effects of Rain .................................... 54
2.5 Effects of Atmospheric Turbulence on Optical
Propagation ............................................... 55
2.5.1 Scintillations ..................................... 57
2.5.2 Beam Wander and Angle of Arrival of Optical Wave ... 63
2.6 Measurements of Atmospheric Turbulence .................... 80
2.7 Modeling of Atmospheric Optical Turbulence ................ 82
2.7.1 Analytical Models .................................. 82
2.7.2 Empirical and Semi-Empirical Models ................ 83
2.7.2.1 Concept and Applications of Thiermann
(MOS) Model ............................... 84
2.7.2.2 Macroscale Meteorological Model ........... 87
2.7.2.3 Extension of the Macroscale
Meteorological Model ...................... 92
2.8 Line-of-Sight Bending Caused by Strong Atmospheric
Turbulence ................................................ 97
2.8.1 Modeling of Line-of-Sight Bending .................. 99
2.8.2 Boundary Layer Turbulence Modeling ................ 100
2.8.3 Fluctuations of the Refractive Index .............. 104
2.8.4 Line-of-Sight Bending Prediction .................. 107
References .................................................... 114
Chapter 3 Applied Aspects of Lidar ........................... 123
3.1 Turbulence Profile Measurement with Lidar ................ 125
3.1.1 Imaging Lidar Principle ........................... 126
3.1.2 Practical Considerations .......................... 131
3.1.3 Lidar Inaccuracy .................................. 134
3.1.4 C2n Retrieval Technique ............................ 141
3.2 Lidar Research of Passive Scalar Field Fluctuations ...... 144
3.2.1 Lidar Method for Turbulence Spectrum Estimation ... 145
3.3 Lidar Measurement of Atmospheric Aerosol Parameters ...... 152
References .................................................... 162
Chapter 4 Optical Communication Channels ..................... 171
4.1 Main Characteristics ..................................... 171
4.1.1 Block Diagram of the Communication System ......... 173
4.1.2 Link Budget ....................................... 176
4.2 Key Parameters Prediction ................................ 180
4.3 Mathematical and Statistical Description of Signal
Fading ................................................... 181
4.3.1 Lognormal Probability Density Function ............ 183
4.3.2 Gamma-Gamma Density Distribution Function ......... 184
4.3.3 K Probability Density Distribution Function ....... 186
4.4 Modulation Methods ....................................... 186
4.4.1 On-Off Keying Modulation .......................... 188
4.4.2 Pulse Amplitude Modulation ........................ 193
4.4.3 Pulse Position Modulation ......................... 194
4.4.4 The Effect of Turbulence on OOK System Analysis ... 195
4.4.5 Mitigating Atmospheric Turbulence Effects ......... 198
4.4.6 Performance of an OWC as a Function of
Wavelength ........................................ 198
References .................................................... 201
Chapter 5 Channel and Signal Data Parameters in Atmospheric
Optical Communication Links ........................ 205
5.1 Irradiance PDF ........................................... 206
5.1.1 Gamma-Gamma Distribution .......................... 207
5.1.2 Ricean Distribution ............................... 208
5.2 Key Parameters of Data Stream in Optical Channels with
Fading ................................................... 210
5.2.1 BER of Optical Channel ............................ 210
5.2.2 Channel Capacity and Spectral Efficiency .......... 211
5.2.2.1 Classical Approach ....................... 212
5.2.2.2 Approximate Approach ..................... 213
5.3 Modeling of Key Parameters of the Channel and
Information Data ......................................... 218
5.4 Summary .................................................. 235
References .................................................... 236
Abbreviations ................................................. 241
Index ......................................................... 245
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