Majumdar / Ricklin Free-Space Laser Communications

Principles and Advances
1. Auflage 2010
ISBN: 978-0-387-28677-8
Verlag: Springer US
Format: PDF
Kopierschutz: 1 - PDF Watermark

E-Book, Englisch, Band 2, 418 Seiten

Reihe: Optical and Fiber Communications Reports

This is a comprehensive tutorial on the emerging technology of free-space laser communications (FSLC). The book offers an all-inclusive source of information on the basics of FSLC, and a review of state-of-the-art technologies. Coverage includes atmospheric effects for laser propagation and FSLC systems performance and design. Free-Space Laser Communications is a valuable resource for engineers, scientists and students interested in laser communication systems designed for the atmospheric optical channel.

Arun K. Majumdar Ph.D., is Director of Research at LCResearch, Inc. in California. He has more than 23 years of experience from Industry, University and National Laboratory settings in the areas of atmospheric turbulence effects on laser propagation, imaging and communications. He received his Ph.D. in Electrical Engineering from the University of California, Irvine.

Jennifer C. Ricklin received her Ph.D. in electrical engineering from the Johns Hopkins University. She has been with the Army Research Laboratory since 1983. Since that time her research interests have included a number of topical applications of laser beam propagation in the atmosphere. She is now a Program Manager at DARPA / ATO.

Autoren/Hrsg.

Majumdar, Arun K.

Ricklin, Jennifer C

Inhaltsverzeichnis

1;Preface;6
2;Contributors;10
3;Table of Contents;12
4;Introduction;13
4.1;1. Introduction;13
4.1.1;1.1. Brief History;14
4.1.2;1.2. Applications;15
4.1.3;1.3. Advantages and Challenges;15
4.1.4;1.4. Limitations;15
4.1.5;1.5. Basics of Operation;16
4.2;2. Understanding Free-Space Laser Communications Systems Performance;17
4.2.1;2.1. Bit Error Rate;17
4.2.2;2.2. Fundamental Limit of Light Detection;17
4.2.3;2.3. BER for a Random Stochastic Communication Channel;18
4.2.4;2.4. Wavelength Selection Criteria;19
4.2.5;2.5. Adaptive Optics for Free-Space Laser Communications;19
4.2.6;2.6. Coding for Atmospheric Channel;19
4.3;3. Summary;20
4.4;Acknowledgement;20
4.5;References;20
5;Atmospheric channel effects on free-space laser communication;21
5.1;1. Introduction;21
5.2;2. Beam Extinction Due to Atmospheric Aerosols and Molecules;22
5.2.1;2.1. Extinction;22
5.2.2;2.2. Molecular Extinction;23
5.2.3;2.3. Molecular Transmittance Codes;24
5.2.4;2.4. Aerosol Extinction;25
5.2.5;2.5. Mie Theory;27
5.2.6;2.6. Aerosol Models;29
5.2.7;2.7. Atmospheric Attenuation of Laser Power;31
5.3;3. Channel Effects Due to Optical Thrbulence;32
5.3.1;3.1. Refractive Index Structure Parameter C2n;32
5.3.2;3.2. Optical Turbulence Models;35
5.3.2.1;3.2.1. PAMELA Model;35
5.3.2.2;3.2.2. Gurvich Model;40
5.3.2.3;3.2.3. SLC-Day Model;42
5.3.2.4;3.2.4. Hufnagel-Valley Model;42
5.3.2.5;3.2.5. HV-Night Model;43
5.3.2.6;3.2.6. Greenwood Model;43
5.3.2.7;3.2.7. Other Thrbulence Models;44
5.3.3;3.3. Free-Space Laser Communication in Optical Turbulence;45
5.3.3.1;3.3.1. Free-Space Laser Beam Propagation;45
5.3.3.2;3.3.2. Laser Beam Propagation in Optical Turbulence;46
5.3.3.3;3.3.3. Scintillation Index and Aperture Averaging;48
5.3.3.4;3.3.4. Beam Wander;52
5.3.3.5;3.3.5. Bit Error Rate Determination for a Direct-Detection Binary Optical Communication Link;52
5.3.3.6;3.3.6. Reducing Optical Turbulence Effects;56
5.4;Acknowledgments;56
5.5;Appendix A: Mathcad Version of PAMELA Model;57
5.5.1;PAMELA inputs;57
5.5.2;Calculate Solar Insolation I, Irradiance R, Sensible Heat Flux H;57
5.5.3;Calculate Pasquill Stability Class;57
5.5.4;Calculate Flux Profile Relationships;57
5.5.5;Calculate Cn2;58
5.5.6;Date, time,and location inputs;58
5.5.7;Meteorological and Terrain Inputs;58
5.5.8;Change degrees Fahrenheit to Kelvin;58
5.5.9;Calculate radiation class Cr;59
5.5.10;Calculate wind speed class cw;59
5.5.11;Calculate Monin-Obukhov Length L;59
5.5.12;Estimate dimensionless wind shear .m ;60
5.5.13;Estimate dimensionless temperature gradient .h;60
5.5.14;Estimate characteristic temperature Tstar;60
5.5.15;Estimate gradient for refractive index fluctuations;60
5.5.16;Estimate eddy dissipation rate e;61
5.6;Appendix B: Calculating Solar Iirradiance and Sensible Heat Flux;61
5.7;Appendix C: Calculation of Aperture-Averaged Scintillation Index Using Mathcad;62
5.7.1;Rytov variance;62
5.7.2;focusing parameter;62
5.7.3;diffractive parameter;63
5.7.4;beam size (radius) at the receiver;63
5.7.5;Aperture-averaging Factor A;63
5.7.6;Aperture-averaged scintillation index;64
5.7.7;References;64
6;Free-space laser communication performance in the atmospheric channel;69
6.1;1. Introduction;69
6.2;2. Basics of Laser Communication Link Analysis;71
6.2.1;2.1. Communication Channel Characterization;71
6.2.2;2.2. Transmitter and Receiver System;72
6.2.3;2.3. Link Analysis;72
6.2.3.1;2.3.1. Data Rate;74
6.2.3.2;2.3.2. Link Margin;74
6.2.3.3;2.3.3. Bit Error Rate in Presence of Atmospheric Absorption and Scattering;74
6.2.3.4;2.3.4. Example Numerical Results;76
6.2.4;2.4. Optical Link Reliability;82
6.3;3. Laser Communication Performance Prediction and Analysis Under Scintillation Conditions;84
6.3.1;3.0.1. Hufnagel-Valley Model;85
6.3.2;3.1. Scintillation index: Point Receiver and Aperture Averaged Variance;85
6.3.2.1;3.1.1. Plane Wave;87
6.3.2.2;3.1.2. Spherical Wave;87
6.3.2.3;3.1.3. Gaussian beam wave [14];87
6.3.3;3.2. Probability Density Function (pdf) Models;88
6.3.4;3.3. Received Signal-to-Noise -Ratio (SNR) and Bit-Error-Rate (BER);91
6.3.4.1;3.3.1. Relationship between SNR and BER;91
6.3.4.2;3.3.2. Why Atmospheric Turbulence Increases the Bit Error Rate?;92
6.3.4.3;3.3.3. Bit-Error Rate Computation for OOK Modulation;93
6.3.4.4;3.3.4. Bit-Error Rate Computation for Pulse Position Modulation(PPM) : Some Basics;94
6.3.5;3.4. Probability of Fade;95
6.4;4. Example Numerical Results;96
6.4.1;4.1. Example I : Uplink (Spherical Wave/OOK);96
6.4.2;4.2. Example 2: Downlink (Plane Wave/OOK);99
6.4.3;4.3. Example 3: Horizontal: Terrestrial Link (Gaussian Beam Wave/OOK);101
6.4.4;4.4. Example 4: Downlink PPM Laser Communication in Presence of Atmospheric Turbulence and Multiple Scattering Media;104
6.4.4.1;4.4.1. Theory and Formulation of BER for PPM with Stretched Pulses for Pulse Position Modulation;104
6.4.4.2;4.4.2. BET-Error-Rate (BER) and Slot Count Statistics;107
6.4.4.3;4.4.3. The Impulse Response Function in the Case of Multiple Scattering;108
6.4.4.4;4.4.4. Numerical Results;109
6.4.4.5;4.4.5. BER Computation for Both Turbulence and Multiple Scattering Media;110
6.5;5. Other Examples/Scenariosof Free-Space Optical and Laser Communications;112
6.5.1;5.1. Ground to Space Shuttle Link;112
6.5.2;5.2. UAV-to-Ground Lasercom Link;112
6.5.2.1;5.2.1. Indoor Optical Communication;112
6.5.2.2;5.2.2. Free-space Optical Interconnect;113
6.6;6. Multiple Transmitters/Receivers Approach for Lasercomm;114
6.7;7. Conclusion;116
6.8;Acknowledgments;117
6.9;References;117
7;Laser communication transmitter and receiver design;121
7.1;1. Introduction;121
7.1.1;1.1. Background;123
7.1.2;1.2. Scope;127
7.1.3;1.3. Historical Perspective;127
7.2;2. General Wavelength Considerations;129
7.2.1;2.1. Carrier Characteristics;129
7.2.2;2.2. Electromagnetic Signaling Options;131
7.2.2.1;2.2.1. Overview of FSO Modulation Formats and Sensitivities;132
7.2.2.1.1;2.2.1.1. On-Off-Keying (OOK);133
7.2.2.1.2;2.2.1.2. Differential-Phase-Shift-Keying (DPSK);134
7.2.2.1.3;2.2.1.3. Phase-Shift-Keying (PSK);135
7.2.2.1.4;2.2.1.4. M -ary Orthogonal Modulation;135
7.2.2.1.5;2.2.1.5. M-ary Pulse-Position Modulation (M-PPM);137
7.2.2.1.6;2.2.1.6. M-ary Frequency-Shift Keying (M-FSK);139
7.2.2.1.7;2.2.1.7. Polarization-Shift-Keying (PoISK);140
7.2.3;2.3. Comparison of RF and Optical Properties;140
7.2.3.1;2.3.1. Diffraction;140
7.2.3.2;2.3.2. Optical Detection;141
7.2.3.3;2.3.3. Technology Limitations;142
7.2.3.4;2.3.4. Average and Peak Power Limited Transmitters;143
7.2.3.5;2.3.5. Quantum Noise Limitations;144
7.2.3.6;2.3.6. Quantum-limited Direct Detection (DD);147
7.2.3.7;2.3.7. Thermal Noise;150
7.2.4;2.4. Example Sensitivities and Link Budget;153
7.3;3. Transmitter Technologies;154
7.3.1;3.1. Direct Modulation and Semiconductor Laser Sources;155
7.3.1.1;3.1.1. Spectral Shaping;156
7.3.2;3.2. Semiconductor Laser Structures;158
7.3.3;3.3. Laser Wavelength Control;159
7.3.4;3.4. Cavity-Dumped and Q-Switched Lasers;161
7.3.5;3.5. Master Oscillator Power Amplifier (MOPA);162
7.3.5.1;3.5.1. Modulation;162
7.3.5.2;3.5.2. Mach-Zehnder Modulator (MZM);163
7.3.5.2.1;3.5.2.1. MZM Phase Elements;165
7.3.5.2.2;3.5.2.2. MZM Bias Control;166
7.3.5.2.3;3.5.2.3. Extinction Ratio (ER);166
7.3.5.2.4;3.5.2.4. Extinction Ratio Characterization and Optimization;167
7.3.5.2.5;3.5.2.5. MZM Drive Powerand Chirp Considerations;169
7.3.5.2.6;3.5.2.6. Pulsed Waveform Generation;171
7.3.5.3;3.5.3. High Power Optical Amplifier;173
7.3.5.3.1;3.5.3.1. Average Power Limited (APL) Properties;175
7.3.5.3.2;3.5.3.2. Amplifier Gain, Saturation, and Noise;175
7.3.5.3.3;3.5.3.3. Amplifier Efficiency;177
7.3.5.3.4;3.5.3.4. Polarization-Maintaining (PM) Fiber Amplifier Designs;180
7.3.5.4;3.5.4. High-Efficiency Semiconductor Optical Amplifiers;182
7.3.5.5;3.5.5. Arbitrary Waveforms and Variable-Duty-Cycle Signaling;184
7.3.5.5.1;3.5.5.1. Low Duty Cycle Limitations;186
7.3.5.5.2;3.5.5.2. A) Limited TX Modulation Extinction;186
7.3.5.5.3;3.5.5.3. B) Transmitter ASE;186
7.3.5.5.4;3.5.5.4. C) Nonlinear Impairments;188
7.4;4. Receiver Technologies;193
7.4.1;4.1. Direct Detection-PIN;193
7.4.2;4.2. Direct Detection Avalanche-Photodiode (APD);195
7.4.3;4.3. Direct Detection-Photon Counting;196
7.4.4;4.4. Coherent Homodyne Receivers ;197
7.4.5;4.5. Optically Preamplified Direct Detection;198
7.5;5. Performance and Implementation Considerations;201
7.5.1;5.1. Waveform and Filtering Considerations;202
7.5.1.1;5.1.1. Symmetric Filtering;204
7.5.1.2;5.1.2. Gaussian Waveforms and Matched Optical Filtering;205
7.5.1.2.1;5.1.2.1. Relaxed Filter Tolerances;205
7.5.1.2.2;5.1.2.2. Reduced Sensitivity to Timing Jitter;207
7.5.1.2.3;5.1.2.3. Combined Optical and Postdetection Filtering;209
7.5.1.3;5.1.3. Optimized Multi-Rate Transceivers;211
7.5.2;5.2. Differential Phase Shift Keying (DPSK);212
7.5.2.1;5.2.1. DPSK Wavelength Alignment Considerations;213
7.5.2.2;5.2.2. Interferometer Stabilization;215
7.5.2.3;5.2.3. Multi-Wavelength DPSK Receiver Options;218
7.5.2.4;5.2.4. Reconfigurable DPSK Demodulators;221
7.5.3;5.3. Hybrid Modulation Formats;222
7.5.4;5.4. Demonstrated Communication Performance;223
7.5.5;5.5. Applications: to the Moon and Beyond;227
7.6;Acknowledgments;230
7.7;Acronyms andAbbreviations;232
7.8;References;234
7.9;Symbols;231
8;Free-space laser communications with adaptive optics: Atmospheric compensation experiments;259
8.1;1. Introduction;260
8.2;2. Adaptive Optics Architectures for Free-Space Optical Communication Systems;261
8.3;3. Experimental System Arrangement and Components;264
8.4;4. Compensation of Low-Order Distortions;267
8.4.1;4.1. Tracking and Fast Beam Steering System;267
8.4.2;4.2. Compensation of Atmospheric Wave-Front Tilt Distortions;269
8.4.3;4.3. Laser Communication with Tip/Tilt Control;270
8.5;5. SPGD High-Resolution Wave-Front Control;272
8.5.1;5.1. SPGD Adaptive Optics System;272
8.5.2;5.2. Temporal Behavior of the Received Power in the Tip/Tilt-Compensated Receiver System;273
8.5.3;5.3. Wave-Front Control with the SPGD AO System;274
8.5.4;5.4. SPGD Adaptive Transceiver System;279
8.6;6. Summary and Conclusion;280
8.7;Acknowledgment;281
8.8;References;281
9;Optical networks, last mile access and applications;285
9.1;1. Optical Networks;286
9.1.1;1.1. Types of FSO Systems for Different Network Architectures;286
9.1.2;1.2. Architectures of FSO Networks (Point-to-Point and Point-to-Multipoint Configurations);288
9.1.2.1;1.2.1. Optical Wireless in Ring Architecture;288
9.1.2.2;1.2.2. Optical Wireless in Star Architecture;289
9.1.2.3;1.2.3. Optical Wireless in Meshed Architecture;290
9.1.3;1.3. Connecting to the Backbone;290
9.2;2. FSO Applications;291
9.2.1;2.1. Short Range Aapplications and Last Mile Access;293
9.2.1.1;2.1.1. FSO in Combination with Satellite and Wireless LAN;296
9.2.2;2.2. Long Range Applications;296
9.2.3;2.3. Space Applications (Aircraft and Satellites);299
9.3;3. Last Mile;301
9.3.1;3.1. Line of Sight;301
9.3.2;3.2. Reliability and Availability;303
9.3.3;3.3. Different FSO Techniques for the Last Mile;306
9.3.3.1;3.3.1 Small FSO System for 100 m;307
9.3.3.2;3.3.2. FSO System for 300 m;307
9.3.4;3.4. FSO network for a Small City and Multimedia Applications;308
9.3.4.1;3.4.1. Multimedia Applications;308
9.3.4.2;3.4.2. FSO Network for a Small City;309
9.4;4. Summary;312
9.5;References;313
10;Communication techniques and coding for atmospheric turbulence channels;315
10.1;1. Introduction;316
10.2;2. Modeling of Optical Communication through Atmospheric Turbulence;317
10.2.1;2.1. Modeling of Atmospheric Turbulence;318
10.2.2;2.2. Spatial and Temporal Coherence of Optical Signals through Turbulence;318
10.2.3;2.3. Probability Distributions ofTurbulence-Induced Intensity Fading;320
10.2.3.1;2.3.1. Marginal Distribution of Fading;320
10.2.3.2;2.3.2. Joint Spatial and Temporal Distributions of Fading;321
10.3;3. Maximum-Likelihood Detection of On-Off Keying in Thrbulence Channels;322
10.3.1;3.1. Symbol-by-Symbol Maximum-Likelihood Detection;323
10.3.2;3.2. Maximum-Likelihood Sequence Detection;325
10.4;4. Spatial Diversity Reception;325
10.4.1;4.1. Maximum-Likelihood Diversity Detection on Turbulence Channels;325
10.4.2;4.2. Numerical Simulationfor Dual Receivers;327
10.4.3;4.3. Summary;328
10.5;5. Temporal Domain Techniques;329
10.5.1;5.1. Markov Chain Model in Maximum-Likelihood Sequence Detection through Turbulence;329
10.5.1.1;5.1.1 . Joint Temporal Distribution for Turbulence Induced Fading;329
10.5.1.2;5.1.2. Single-Step MC Model for Fading Correlations;330
10.5.1.3;5.1.3. Burst Error Distribution for Symbol-by-Symbol Detection;330
10.5.1.4;5.1.4. Sub-Optimal Per-Survivor Processing for MLSD;333
10.5.2;5.2. Pilot-Symbol Assisted Detectionfor Correlated Turbulent Free-Space Optical Channels;336
10.5.2.1;5.2.1. Pilot-Symbol Assisted Maximum-Likelihood Detection;337
10.5.2.2;5.2.2. Pilot-Symbol Assisted Symbol-by-Symbol Detection with Variable Threshold;339
10.5.2.3;5.2.3. Numerical Simulation;340
10.5.3;5.3. Experimental Demonstration on Temporal Domain Techniques;340
10.6;6. Performance Bounds for Coded Free-Space Optical Communication Through Atmospheric Turbulence;344
10.6.1;6.1. Pairwise Codeword-Error Probability Bound;345
10.6.2;6.2. Error-Probability Bounds for Various Coding Schemes;347
10.6.2.1;6.2.1. Block Codes;347
10.6.3;6.3. Convolutional Codes;348
10.6.3.1;6.3.1. Turbo Codes;350
10.6.4;6.4. Numerical Simulation Results;351
10.6.5;6.5. Summary;353
10.7;Conclusions;354
10.8;Acknowledgment;355
10.9;References;355
11;Optical communications in the mid-wave IR spectral band;359
11.1;1. Introduction;360
11.2;2. Atmospheric Modeling;361
11.2.1;2.1. Atmospheric Turbulence;364
11.2.1.1;2.1.1. Rytov Variance;365
11.2.1.2;2.1.2. Coherence Length;366
11.2.2;2.2. Beam Diameter;367
11.2.3;2.3. Direct Detection SNR;369
11.2.4;2.4. Large Scale and Small Scale Turbulence - Spherical Waves;370
11.2.5;2.5. Bit Error Rate (BER) and Minimum SNR;371
11.3;3. The MWIR Optical Sources;374
11.3.1;3.1. Semiconductor Based Lasers;374
11.3.1.1;3.1.1. Lead-Salt Lasers;375
11.3.1.2;3.1.2. III-V Strained Quantum-Well Lasers;375
11.3.1.3;3.1.3. Quantum Cascade Lasers;375
11.3.1.4;3.1.4. Solid-State Lasers;376
11.3.1.5;3.1.5. Chemical Lasers;377
11.3.2;3.2. Nonlinear Frequency Converters;377
11.3.2.1;3.2.1. Performance Modeling of OPOs;381
11.3.2.2;3.2.2. PPLN OPOs;381
11.3.2.3;3.2.3. Oscillation Threshold Calculations;382
11.4;4. The MWIR Detectors;384
11.4.1;4.1. Dember Effect Detectors;384
11.5;5. Data Communications in the Mid-IR;386
11.5.1;5.1. Weapon Code Transmission in MWIR;387
11.5.1.1;5.1.1. Wavelength Selection;388
11.5.1.2;5.1.2. Transceiver Design Approach;388
11.5.1.3;5.1.3. Experimental Results;392
11.5.2;5.2. Image Transmission in MWIR using an OPO;397
11.6;6. Summary and Conclusions;401
11.7;References;401
12;Quantum cascade laser-based free space optical communications;405
12.1;1. Introduction;405
12.2;2. High Frequency Analog and Digital Modulation;406
12.2.1;2.1. Stability for NIR-Laser and a QCL-Based FSO Link Under Strong Scattering;408
12.3;3. Experimental Apparatus;408
12.3.1;3.1. Satellite TV Transmission Using a QCL-Based FSO Link;414
12.4;Acknowledgments;417
12.5;References;417
13;All-weather long-wavelength infrared free spaceoptical communications;419
13.1;1. Introduction;419
13.2;2. Atmospheric Transmission: The Case for LWIR;420
13.2.1;2.1. Molecular Absorption Model;420
13.2.2;2.2. Smoke Extinction Model;420
13.2.3;2.3. Fog Extinction Model;423
13.3;3. Component Development for LWIR Communications;423
13.3.1;3.1. Compact RF-Driven Laser;423
13.3.2;3.2. Stark-Effect Modulator;424
13.3.3;3.3. Dielectric Waveguide Modulator;425
13.3.4;3.4. AC Biasing Method;426
13.4;4. Experimental Results;427
13.5;References;429

Leseproben

"Communication techniques and coding for atmospheric turbulence channels (p. 303-304)

Abstract. In free -space optica l communication link s, atmo spheri c turbulence causes fluctuations in both the inten sity and the phase of the received light signal, impairing link performance. In this paper , we describe severa l communication techniques to mitigate turbulence-induced intensity fluctuation s, i.e., signal fading . The se techniques are applicable in the regime in which the receiv er aperture is smaller than the correlation length of the fading, and the observation interval is shorter than the correlation time of the fading. We assume that the receive r has no knowledge of the instantaneous fading state . The techniques we con sider are based on the stati stical properties of fading, as functions of both temporal and spatial coordinates. Our approaches can be divided into two categories : temporal domain techniques and spatial domain techniques.

In the spatial domain techniques, one must employ at least two receivers to collect the signal light at different positi ons or from different spatial angle s. Spatial diver sity reception with mult iple recei vers can be used to overcome turbulence-induced fading. When it is not possible to place the receivers sufficiently far apart, the fading at different receivers is correl ated , redu cing the diversity gain . We descr ibe a ML dete ction techn ique to reduce the diver sity gai n penalty caused by such fadin g correl ation.

In the temporal domain techniques, one empl oys a single receiver. When the receiver knows only the marginal statistics of the fading , a symbol-by-symbol ML dete ctor can be used to optimize perform ance. When the receiver also knows the temporal correlation of the fadin g, maximum -likelihood sequence detection (MLSD) can be employed, yielding a further perform ance improvement, but at the cos t of very high complexity. We descri be two reduced-compl exity implementations of the MLSD, which make use of a single-s tep Markov chain model for the fading co rrelation in conjunction with per-survivorprocessing. Next,we also investigate the performance of using error-control codingand pilotsymbol-assisted detectionschemesthroughatmospheric turbulence channels.

1. Introduction

Recently, free-space optical communication has attracted considerable attention for a variety of applications [1-8] . Because of the complexity associated with phase or frequency modulation, current free-space optical communication systems typically use intensity modulation with direct detection (IMIDO). However, in practice, the performance of free-space optical communication systems can be degraded by many effects, such as fog, obstruction of the line-of-sight path, atmospheric turbulence and the nonideal characteristics of optical transmitters and receivers. In this chapter, we focus on communication techniques and coding schemes to counter the degradation caused by atmospheric turbulence in IMIDO links."