Principles and Applications of Free Space Optical Communications

Cover
Contents
List of acronyms
1 Introduction to free space optical (FSO) communications
	1.1 Introduction
	1.2 Free space optics
	1.3 FSO applications
	1.4 Key features and advantageous
	1.5 FSO networks
	1.6 Factors affecting FSO systems
	1.7 FSO link reliability
	References
2 Free-space optical communication over strong atmospheric turbulence channels
	2.1 Introduction
	2.2 Turbulence model
	2.3 OAM multiplexing
	2.4 Dealing with atmospheric turbulence effects by adaptive optics and LDPC coding
	2.5 Concluding remarks
	References
3 Performance analysis and mitigation of turbulence effects using spatial diversity techniques in FSO systems over combined channel
	3.1 Introduction
	3.2 Combined channel model
		3.2.1 Atmospheric attenuation
		3.2.2 Atmospheric turbulence
		3.2.3 Misalignment fading or pointing errors
		3.2.4 Combined channel model
	3.3 Techniques for improving the reliability of FSO systems
		3.3.1 Aperture averaging
		3.3.2 Diversity techniques
		3.3.3 Relaying techniques
	3.4 Transmitter diversity in strong atmospheric turbulence channel using Polsk scheme
		3.4.1 The FSO System with wavelength or time diversity
		3.4.2 Channel model
		3.4.3 Average BER
		3.4.4 Outage probability
	3.5 Multiple input multiple output
		3.5.1 ABER analysis of PolSK
		3.5.2 BER of Polsk with and without pointing errors
			3.5.2.1 ABER without pointing errors
			3.5.2.2 ABER with pointing errors
	3.6 Summary
	Appendix A
	References
4 Link budget for a terrestrial FSO link and performance of space time block codes over FSO channels
	4.1 Introduction
		4.1.1 Terrestrial FSO
	4.2 Channel modeling
		4.2.1 Gamma–gamma distribution
	4.3 Link budget
		4.3.1 Geometric loss
		4.3.2 Attenuation due to atmospheric turbulence
		4.3.3 Rytov approximation
		4.3.4 Andrews's method
		4.3.5 Atmospheric extinction loss
		4.3.6 Link budget
			4.3.6.1 Variation of parameters with link distance
			4.3.6.2 Variation of parameters with weather conditions
			4.3.6.3 Required transmitted power
	4.4 Diversity
		4.4.1 Space diversity
		4.4.2 Space-time diversity
		4.4.3 Alamouti space-time code
			4.4.3.1 Description of 2 ×1 Alamouti scheme
			4.4.3.2 The encoding and transmission sequence
			4.4.3.3 The combining scheme
			4.4.3.4 The maximum likelihood decision rule
		4.4.4 Description of 2 × 2 Alamouti scheme
			4.4.4.1 The encoding and transmission sequence
			4.4.4.2 The combining scheme
			4.4.4.3 The maximum likelihood decision rule
		4.4.5 Modified Alamouti code
	4.5 STBCs derived from non binary cyclic codes
		4.5.1 Cyclic code
		4.5.2 Rank distance
		4.5.3 Transform domain description of cyclic codes
		4.5.4 Cyclotomic coset
		4.5.5 Gaussian integer map [19]
			4.5.5.1 Decoding of STBC derived from non binary cyclic code
		4.5.6 Description of non binary cyclic code used
	4.6 Results
		4.6.1 Comparison of the Alamouti scheme and STBCs derived from non binary cyclic code
	4.7 Conclusions and scope for future work
	References
5 FSO channel—atmospheric attenuation and refractive index (Cn2) modeling as the function of local weather data
	5.1 Introduction
	5.2 Design of FSO link experimental test-bed
	5.3 Measurement of atmospheric attenuation (Aatt) and turbulence strength (Cn2)
	5.4 Existing attenuation and turbulence models
		5.4.1 Atmospheric optical attenuation
		5.4.2 Atmospheric optical turbulence strength (Cn2)
	5.5 Design of regressive model for attenuation and Cn2 estimation
		5.5.1 Atmospheric attenuation (Aatt) model
		5.5.2 Atmospheric turbulence strength (Cn2) model
	5.6 Experimental validation of prediction accuracy of proposed models
		5.6.1 Comparison of predicted and measured Aatt data
		5.6.2 Comparison of predicted and measured Cn2 data
	References
6 Spectral analysis and mitigation of beam wandering using optical spatial filtering technique in FSO communication
	6.1 Introduction
	6.2 Pinhole as the optical spatial filter
	6.3 Pinhole and cone reflector as the optical spatial filter
	6.4 Pinhole, cone reflector, and multi-mode fiber as the optical spatial filter
	References
7 Characterization of atmospheric turbulence effects and their mitigation using wavelet-based signal processing
	7.1 Introduction
	7.2 Atmospheric turbulence effects
		7.2.1 Scintillations
			7.2.1.1 Saturation of scintillations
			7.2.1.2 Aperture averaging
			7.2.1.3 Modification in determination of scintillation index
		7.2.2 Beam wandering
		7.2.3 Beam-pointing stability
	7.3 Free space optical link experimental set-up and data acquisition
		7.3.1 Transmitter and receiver design
		7.3.2 Experimental set-up of 50 m folded free space optical link
			7.3.2.1 Signal capture procedure
		7.3.3 Theoretical fit to the laser beam power profile
		7.3.4 Controlled environment experimental set-up
	7.4 Experimental analysis of turbulence effects
		7.4.1 Analysis of the beam wandering
		7.4.2 Signal statistics over a day and correlation with atmospheric parameters
		7.4.3 Correlation of turbulence-related data with atmospheric parameters
		7.4.4 Positional shift measurement
	7.5 Turbulence effects mitigation using wavelets
		7.5.1 Introduction to wavelet-based discrete signal processing
		7.5.2 Compensation of the atmospheric turbulence-induced distortion using wavelet-based signal processing
		7.5.3 Information recovery
			7.5.3.1 Average bit error rate ratio
	References
8 All-optical relay-assisted FSO systems
	8.1 Introduction
		8.1.1 Fading mitigation techniques
		8.1.2 Relay-assisted FSO communications
	8.2 All-optical amplify-and-forward relay-assisted systems under turbulence effects
		8.2.1 All-optical amplify-and-forward
			8.2.1.1 Performance analysis of triple-hop AOAF FSO
		8.2.2 AOAF numerical analysis
		8.2.3 Experimental analysis for single, dual-hop, and triple-hop AF systems
	8.3 All-optical regenerate-and-forward relaying technique
		8.3.1 Self-phase modulation-based 2R regenerator
		8.3.2 Experimental analysis of AORF FSO
	8.4 Conclusions
	References
9 Optical spatial diversity for FSO communications
	9.1 Introduction
	9.2 Outdoor channel
	9.3 Visibility and fog models
		9.3.1 Kruse model
		9.3.2 Kim model
		9.3.3 Naboulsi model
	9.4 Wavelength diversity to mitigate fog
	9.5 Atmospheric turbulence model and mitigation
		9.5.1 Lognormal turbulence model
		9.5.2 The gamma–gamma turbulence model
	9.6 Turbulence-induced fading mitigation methods
		9.6.1 Aperture averaging
		9.6.2 Spatial diversity
		9.6.3 MIMO system
	9.7 Conclusion
	References
10 Analysis of the effects of aperture averaging and beam width on a partially coherent Gaussian beam over free-space optical communication links
	10.1 Introduction
	10.2 Background and motivation
	10.3 An overview of free-space optical communications
		10.3.1 System description
		10.3.2 Gaussian-beam wave
		10.3.3 Free-space optical communication channel
			10.3.3.1 Atmospheric loss
			10.3.3.2 Optical turbulence in the atmosphere
			10.3.3.3 Pointing errors
			10.3.3.4 Combined channel fading model
		10.3.4 Aperture averaging phenomenon
			10.3.4.1 Extended Huygens–Fresnel principle
			10.3.4.2 Spatial covariance of irradiance fluctuations
	10.4 Performance analysis
		10.4.1 Bit-error rate
		10.4.2 Probability of outage
		10.4.3 Average channel capacity
	10.5 Outage analysis
		10.5.1 Outage probability under light fog condition
		10.5.2 Outage probability under clear weather condition
	10.6 Analysis of the aperture averaging effect
		10.6.1 Error performance due to atmospheric effects
		10.6.2 Average channel capacities due to channel state information
	10.7 Beam width optimization
		10.7.1 Dependence on link design criteria
		10.7.2 Optimum beam width
	10.8 Conclusions
	References
11 Relaying techniques for free space optical communications
	11.1 Introduction
	11.2 System and channel model
	11.3 Outage performance
		11.3.1 Serial DF relaying
		11.3.2 Parallel DF relaying
		11.3.3 Optimization of relay location
		11.3.4 Multi-hop parallel DF relaying
		11.3.5 Serial AF relaying
		11.3.6 Parallel AF relaying
	11.4 Performance results of AF and DF relaying
	11.5 All-optical AF relaying system
	11.6 Summary
	References
12 Experimental test of maximum likelihood thresholds based on Kalman filter estimates in on–off keyed laser communications in atmospheric turbulence
	12.1 Introduction
	12.2 Principle of the method of maximum likelihood thresholds based on Kalman filter estimates
		12.2.1 Probabilistic nature of the propagating signals through atmospheric turbulence
		12.2.2 Maximum likelihood thresholds
		12.2.3 Turbulence-tracking Kalman filter
			12.2.3.1 Initial estimates
			12.2.3.2 Time update equations
			12.2.3.3 Measurement update equations
	12.3 Experimental procedure and results
	12.4 Comparison of threshold approaches
	12.5 Conclusions
	References
13 Signal encryption strategies based on acoustooptic chaos and mitigation of phase turbulence using encrypted chaos propagation
	13.1 A-O Bragg diffraction of profiled optical beams
	13.2 Transfer function formalism (TFF) for arbitrary optical profiles
	13.3 Examination of the nonlinear dynamics under profiled beam propagation
	13.4 Examination of dynamical behavior based on both Lyapunov exponent and bifurcation maps
	13.5 Chaotic encryption and decryption in hybrid acousto-optic feedback (HAOF) devices
	13.6 Preliminary results for chaotic encryption and decryption
	13.7 Propagation of a profiled beam through MVKS type phase turbulence
		13.7.1 An overview
		13.7.2 The von Karman spectrum
		13.7.3 Thin-phase screen generation
	13.8 Spectral approach to the propagation of a (non-chaotic) EM wave through turbulence using SVEA and Fourier transforms
	13.9 A uniform (nonturbulent) propagation prototype
		13.9.1 Propagation through weak turbulence
			13.9.1.1 Propagation through weak turbulence with mean frequency fT = 20 Hz
			13.9.1.2 Propagation through weak turbulence with mean frequency fT = 50 Hz
			13.9.1.3 Propagation through weak turbulence with mean frequency fT = 100 Hz
		13.9.2 Propagation through strong turbulence
			13.9.2.1 Propagation through strong turbulence with mean frequency fT = 20 Hz
			13.9.2.2 Propagation through strong turbulence with mean frequency fT = 50 Hz
			13.9.2.3 Propagation through strong turbulence with mean frequency fT = 100 Hz
	13.10 Spectral approach to encrypted chaotic wave propagation through turbulence using SVEA and Fourier transforms
		13.10.1 Numerical simulations, results, and interpretations
			13.10.1.1 A uniform (nonturbulent) propagation prototype
			13.10.1.2 Chaotic propagation through weak turbulence with mean frequency fT  = 50 Hz
			13.10.1.3 Chaotic propagation through strong turbulence with mean frequency fT = 50 Hz
	13.11 Propagation through phase turbulence using altitude-dependent structure parameter without and with A-O chaos
		13.11.1 Hufnagel-Valley (HV) model
		13.11.2 Plane EM wave propagation through a transparency-thin lens combination with turbulence
		13.11.3 Fixed LT and LD distances for different turbulence strengths
		13.11.4 Fixed C2n and LT for three different (nonturbulent) distances LD
		13.11.5 Fixed C2n and LD, for three different turbulence distances LT
		13.11.6 Modulated EM wave (non-chaotic and chaotic) with a digitized image pattern
		13.11.7 Fixed LT and LD distances for different turbulence strengths under a modulated EM wave propagation
		13.11.8 Fixed C2n and LT for three different destination distances LD
		13.11.9 Fixed C2n and LD for three different destination distances LT
	References
14 Distributed sensing with free space optics
	14.1 Introduction
	14.2 Signals
	14.3 Distributed sensing systems
	14.4 Summary of a distributed system
	14.5 Free space optical communication between two UAVs: BER and adaptive beam divergence analysis
	14.6 Technical issues for mobile UAV FSO communication
		14.6.1 Atmospheric and turbulence effects
		14.6.2 Atmospheric models related to UAV FSO communication links
			14.6.2.1 Hufnagel-Valley (HV) model
			14.6.2.2 Modified Hufnagel-Valley (MHV) model
			14.6.2.3 SLC-Day model
			14.6.2.4 CLEAR1 model
		14.6.3 Alignment and tracking of a FSO communications link to a UAV
	14.7 FSO optical communication system performance in turbulence: BER and SNR calculation
	14.8 Data rate
	14.9 Beam divergence effects for inter-UAV FSO communication
		14.9.1 Adaptive beam divergence technique
	14.10 Results and discussions
	14.11 Conclusions and future research
	References
15 Quantum-based satellite free space optical communication and microwave photonics
	15.1 Introduction to spread spectrum techniques
		15.1.1 Spread spectrum scheme
		15.1.2 Basic building block for quantum spread spectrum
		15.1.3 Incoming data signals
	15.2 Laser satellite communication
	15.3 Free space quantum optical satellite link
	15.4 Analysis of secure key generation rate
		15.4.1 The BB84 QKD Protocol
		15.4.2 The Scarani–Acin–Ribordy–Gisin 2004 (SARG04) QKD Protocol
		15.4.3 The decoy-states protocols
			15.4.3.1 BB84 QKD protocol: vacuum + weak decoy states
			15.4.3.2 The SARG04 QKD protocol: vacuum + two weak decoy states
	15.5 Design parameters and results
	15.6 Introduction to microwave photonics
		15.6.1 Photonics for broadband microwave measurements
			15.6.1.1 Microwave spectrum measurement
			15.6.1.2 Instantaneous frequency measurement (IFM)
		15.6.2 Photonics-based wideband RF signal generation for radar applications
		15.6.3 Photonics radar system—optoelectronic assembly
		15.6.4 Broadband photonics radar system and beamforming architecture
	References
Index
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