Preface
Introduction
Contents
1 Optical Wirelss Coherent Detection: An Overview
1.1 Optical Wireless Coherent Communication
1.2 Optical Wireless Communication: Development Status
1.3 Research Status at Home and Abroad
1.3.1 Inter-Satellite Coherent Optical Detection
1.3.2 Coherent Optical Detection in Optical Fiber Communication
1.3.3 Free-Space Coherent Detection Communication System
1.4 Research Status on Factors Affecting Performance of Free-Space Coherent Detection Systems
1.5 Research Status on Factors Affecting Partially Coherent Beam Coherent Detection System
1.6 Research Status of Wavefront Correction
1.6.1 Research Status of Atmospheric Turbulence Compensation Technology
1.6.2 Research Status of Wavefront Correction Technology Abroad
1.6.3 Domestic Research Status of Wavefront Correction Technology
References
2 Coherent Optical Communication
2.1 Basic Principles of Coherent Optical Communication
2.1.1 Fundamentals
2.1.2 Homodyne Detection
2.1.3 Heterodyne Detection
2.1.4 Detection of an Amplitude Modulated Signal
2.2 Coherent Modulation and Demodulation
2.2.1 Optical Modulation
2.2.2 Coherent Demodulation
2.2.3 System Performance
2.3 Factors Affecting Detection Sensitivity
2.3.1 Phase Noise
2.3.2 Intensity Noise
2.3.3 Polarization Noise
2.3.4 Key Technologies of Coherent Optical Communication Systems
2.4 Spatial Phase Conditions for Optical Heterodyne Detection
2.4.1 Spatial Phase Difference Conditions
2.4.2 Frequency Conditions
2.4.3 Polarization Conditions
2.5 Homodyne Detection and Heterodyne Detection
2.5.1 Homodyne Coherent Detection
2.5.2 Heterodyne Detection
2.6 Composition of Heterodyne Detection System
2.6.1 Wavefront Correction Module
2.6.2 Polarization Control Module
2.6.3 Laser Frequency Stabilization Module
2.6.4 Balanced Detection Module
2.6.5 Coherent Demodulation Module
2.7 Performance Analysis of Heterodyne Detection System
2.7.1 Signal to Noise Ratio and Detection Sensitivity of Heterodyne Detection System
2.7.2 Performance Analysis of Heterodyne Detection System Under Ideal Conditions
2.7.3 Performance of Heterodyne Detection System with Optical Alignment Error
2.8 Signal-to-Noise Ratio, Bit Error Rate and Detection Sensitivity
2.8.1 Signal-to-Noise Ratio of Direct Detection and Heterodyne Detection
2.8.2 Bit Error Rate of Direct Detection and Heterodyne Detection
2.8.3 Analysis of Detection Sensitivity of Direct and Heterodyne Detection
2.9 Influence of Wavefront Distortion on Spatial Coherent Optical Communication
2.9.1 Principle of Wavefront Distortion
2.9.2 The Effect of Wavefront Distortion
References
3 Spatial Light to Fiber Coupling and Beam Control
3.1 Space Optical-Fiber Coupling Technology
3.1.1 Ideal LensâSingle-Mode Fiber Coupling
3.1.2 Gaussian Beam Coupling
3.2 Spatial Plane Wave-Lens-Single Mode Fiber Coupling Under Weakly Turbulent Atmosphere
3.2.1 Light Field Distribution and Refractive Index Power Spectrum Under Atmospheric Turbulence
3.2.2 Lens Coupling Under Atmospheric Turbulence
3.2.3 Relative Variance in Fluctuation of Lens Coupled Optical Power Under Atmospheric Turbulence
3.2.4 Spatial Optical Coupling of Lens Array Under Atmospheric Turbulence
3.3 Automatic Alignment Algorithm for Spatial LightâOptical-Fiber Coupling
3.3.1 Simulated Annealing Algorithm
3.3.2 Particle Swarm Optimization
3.4 Beam Array Control Based on Maka Antenna
3.4.1 Maka Antenna and Existing Problems
3.4.2 Array Gaussian Beam Control Based on Maka Antenna
3.4.3 Coupling Efficiency of Maka Antenna Under Atmospheric Turbulence
References
4 Beam Polarization Control Technology
4.1 Advances in Beam Polarization Control
4.2 Coherent Optical Communication System with Polarization Control
4.2.1 Representation of Light Polarization
4.2.2 Polarization Control of Coherent Optical Communication Systems
4.3 Coherent Optical Communication Polarization Control Model and Control Algorithm
4.3.1 Polarization Control Model for Coherent Optical Communication Systems
4.3.2 Simulated Annealing Algorithm in Polarization Control
4.3.3 Application of Particle Swarm Algorithm in Polarization Control
4.3.4 Design of SPO Algorithm and Its Application in Polarization Control
4.3.5 Comparison of the Three Algorithms
4.4 Endless Reset of the Polarization Controller
4.4.1 Small Step Backward Reset Method and Direct Reset Method
4.4.2 Experiment of Direct Reset Method
4.5 Experiment of Polarization Control
4.5.1 Experimental Setup
4.5.2 Polarization-Controlled External Field Experiments
References
5 Double Balanced Detection.-Wavefont Correction System
5.1 Domestic and International Development: History and Current Situation
5.1.1 Foreign Developments: History and Current Situation
5.1.2 Domestic Developments: History and Present Situation
5.2 Structure and Principle of Double-Balanced Detection System
5.2.1 Classification of 90° Optical Mixers Used in Double-Balanced Detection Techniques
5.2.2 Classification of Balanced Detectors
5.2.3 Principle of Double-Balanced Detection
5.3 Balance Mismatch Analysis of Double-Balanced Detection Technology
5.3.1 Effect of Mixer
5.3.2 Effect of Balanced Detectors
5.4 Common-Mode Rejection Ratio in Double-Balanced Detection System
5.4.1 Common-Mode Rejection Ratio
5.4.2 Signal-to-Noise Ratio
5.4.3 Numerical Simulation
5.5 Optisystem Simulation of Double-Balanced Detection System
5.5.1 Simulation of Double-Balanced Detection System
5.5.2 Effect of Power Mismatch on the SNR of Double-Balanced Detection
5.5.3 Effect of Time Mismatch on SNR of Double-Balanced Detection
References
6 Adaptive Optics Correction
6.1 Research Status of Adaptive Optics System
6.2 Adaptive Optics System in Coherent Optical Communication
6.2.1 Principles of Adaptive Optics
6.2.2 Wavefront Sensor
6.2.3 Working Principle of Wavefront Corrector
6.3 System Error Analysis
6.3.1 Error Analysis of Adaptive Optics System
6.3.2 Methods to Suppress Systematic Errors
6.4 Implementation of Wavefront Controller
6.4.1 Wavefront Reconstruction Theory
6.4.2 Measurement of Influence Matrix of Deformable Mirror
6.4.3 Realization of Wavefront Control Algorithm
6.5 Correction of Wavefront Distortion
6.5.1 Analysis of Closed-Loop Control Parameter Adjustment Process
6.5.2 Impact of Wavefront Phase Distortion on Mixing Efficiency
6.5.3 Impact of Mixing Efficiency on Coherent Optical Communication Systems
6.6 Experimental Verification
6.6.1 Analysis of Dynamic Characteristics of Wavefront Controller
6.6.2 Analysis of Wavefront Distortion Correction Effect
References
7 Wavefont Sensorless Adaptive Optics Correction
7.1 Fundamentals of Adaptive Optics
7.1.1 Wavefront Corrector
7.1.2 Wavefront Controller
7.1.3 Stochastic Parallel Gradient Descent Algorithm
7.2 Correction of Wavefront of Aberrated Gaussian Beams Using SPGD Algorithm
7.2.1 Optical Transmission Equation and Multiphase Screen Method
7.2.2 Simulation of Gaussian Beam Transmitted in Atmospheric Turbulence
7.2.3 Signal Optical Wavefront Correction at Various Turbulence Intensities
7.2.4 AO Technology for Improvement of Performance of Coherent Optical Communication System
7.3 Experimental Studies
7.3.1 Correction of Static Wavefront Distortion Using SPGD Algorithm
7.3.2 SPGD Algorithm Wavefront Correction for Outlier Detection Coherent Optical Communication System
References
8 Wavefont Correction Technique of Spatial Coherent Optical Communication with LC-SLM
8.1 Phase Calibration of LC-SLM
8.1.1 LC-SLM Phase Calibration
8.1.2 Structure of LC-SLM
8.1.3 Jones Matrix Analysis of LC-SLM Phase Modulation Principle
8.2 Working Principle of Phase Calibration of LC-SLM
8.2.1 Interference Fringe Shift Method
8.2.2 Working Principle of Interference Fringe Movement Method
8.3 Phase Calibration Experiments
8.3.1 Phase Calibration Experiment of LC-SLM-R
8.3.2 Least Squares Fitting
8.4 LC-SLM-R Spatial Coherent Optical Communication Wavefront Correction System
8.4.1 LC-SLM-R Wavefront Distortion Correction Principle
8.4.2 Structure of Wavefront Correction System
8.5 Principle of Wavefront Measurement
8.5.1 Static Wavefront Measurement of Transverse Shear Interferometer
8.5.2 Shack-Hartmann Real-Time Wavefront Measurement Principle
8.6 Wavefront Reconstruction
8.6.1 Zernike Polynomial
8.6.2 Wavefront Reconstruction Based on Zernike Polynomial
8.7 LC-SLM-R Wavefront Correction Experiment
8.7.1 Static Wavefront Correction Experiment
8.7.2 Field Experiment
References
9 Effect of Beam Mode on Coherent Detection System
9.1 Basic Theory of Pattern Decomposition
9.1.1 Mathematical Model of Incoherent Mode Decomposition
9.1.2 Coherent Module Decomposition
9.2 Effect of Beam Pattern on Performance of Coherent Detection Systems
9.2.1 Mathematical Modeling of Effect of Beam Patterns on Coherent Detection Systems Under Atmospheric Turbulence
9.2.2 Effect of Beam Pattern on Performance of Coherent Detection Systems
9.3 Experimental Results of Coherent Detection Systemâ1.3-km Analysis
9.4 Light Intensity Distribution of Partially Coherent GSM Beams Under Turbulence
9.5 Modal Coefficient Distribution of Partially Coherent GSM Beam Under Turbulence
9.6 Effect of Turbulence on Beam Pattern
9.6.1 Effect of Light Source Parameters on Weighting Factors
9.6.2 Effect of Turbulence Parameters on Weighting Factors
9.6.3 Effect of Transmission Distance on Weighting Factor
9.7 Effect of Turbulence on M2 Factor
9.7.1 Effect of Light Source Parameters and Transmission Distance on M2 Factor
9.7.2 Effect of Atmospheric Turbulence on M2 Factor
9.8 Numerical Simulation
9.8.1 Calculation Method of Numerical Simulation Beam Pattern
9.8.2 Effect of Transmission Distance on Mode Coefficients
9.9 Experimental Studies
9.9.1 Experimental Principle
9.9.2 Experimental Results
References