Optical Fiber Telecommunications V11

Cover
Optical Fiber Telecommunications VII
Copyright
Dedication
List of contributors
Preface: Overview of Optical Fiber Telecommunications VII
	Introduction
	Seven editions
	Ivan P. Kaminow and Tingye Li
	Perspective of the past 6 years
	Acknowledgments
	Chapter highlights
		Optical Fiber Telecommunications VII: Chapter titles, authors, and abstracts
Part I: Devices/Subsystems Technologies
1 Advances in low-loss, large-area, and multicore fibers
	1.1 Introduction
	1.2 Low-loss and large effective area fibers
		1.2.1 Figure of merit of fiber loss and effective area on transmission systems
		1.2.2 Fiber loss mechanism and approaches for lowering fiber loss
		1.2.3 Fiber design for large effective area
		1.2.4 Recent progress on low-loss and large effective area fiber and system results
	1.3 Multicore fibers
		1.3.1 Design parameters and types of multicore fibers
			1.3.1.1 Core pitch
			1.3.1.2 Outer cladding thickness
			1.3.1.3 Cladding diameter
		1.3.2 Coupling characteristics of propagating modes
			1.3.2.1 Uncoupled multicore fibers
			1.3.2.2 Coupled-power theory for uncoupled MCF
				1.3.2.2.1 Discrete coupling model and statistical distribution of the cross talk
			1.3.2.3 Coupled multicore fibers
				1.3.2.3.1 Systematically coupled multicore fiber
				1.3.2.3.2 Randomly coupled multicore fiber
					Mechanism of random mode coupling
					Group delay spread
					Mode-dependent loss
		1.3.3 Various MCFs proposed for communications and progress toward practical realization
	References
2 Chip-based frequency combs for wavelength-division multiplexing applications
	2.1 Wavelength-division multiplexing using optical frequency combs
	2.2 Properties of optical frequency combs
		2.2.1 Center frequency, line spacing, and line count of frequency combs
		2.2.2 Optical linewidth and relative intensity noise
		2.2.3 Comb line power and optical carrier-to-noise power ratio
	2.3 Chip-scale optical frequency comb generators
		2.3.1 Mode-locked laser diodes
		2.3.2 Electro-optic modulators for comb generation
		2.3.3 Gain-switched laser diodes
		2.3.4 Kerr-nonlinear waveguides for spectral broadening
		2.3.5 Microresonator-based Kerr-comb generators
		2.3.6 Comparative discussion
	2.4 Kerr comb generators and their use in wavelength-division multiplexing
		2.4.1 Principles and applications of microresonator comb generators
		2.4.2 Microresonator fabrication
		2.4.3 Application overview of Kerr combs and their spectral coverage
		2.4.4 The physics of Kerr comb generation
		2.4.5 Dissipative Kerr solitons
		2.4.6 Massively parallel wavelength-division multiplexing transmission using dissipative Kerr soliton comb
			2.4.6.1 Data transmission with single and interleaved soliton
			2.4.6.2 Data transmission with solitons both at the transmitter and at the receiver
			2.4.6.3 Progress toward integrated wavelength-division multiplexing transceiver modules
	2.5 Conclusions
	Appendix A
		A.1 Calculation of optical signal-to-noise power ratio (OSNR) at the receiver
		A.2 Required receiver optical signal-to-noise power ratio
	References
3 Nanophotonic devices for power-efficient communications
	3.1 Current state-of-the-art low-power GHz silicon photonic devices
		3.1.1 Carrier manipulation mechanisms
		3.1.2 Photonic designs of silicon modulators
			3.1.2.1 Mach-Zehnder modulators
			3.1.2.2 Resonant modulators
	3.2 Emerging approaches for improving performance via device design
		3.2.1 Novel junction design for improving mode overlap
		3.2.2 Novel resonator design
			3.2.2.1 Robust resonators to fabrication variations
			3.2.2.2 Athermal resonators
		3.2.3 Resonance-free light recycling
	3.3 Emerging approaches for improving performance via material integration
		3.3.1 Materials with strong electro-absorption
			3.3.1.1 Germanium and germanium-silicon alloys
		3.3.2 Materials with improved plasma dispersion effect
			3.3.2.1 III-V semiconductors
		3.3.3 Materials with χ(2) nonlinearity
			3.3.3.1 Organic nonlinear materials
			3.3.3.2 Inorganic nonlinear materials
		3.3.4 Two-dimensional materials
	3.4 Concluding remarks
	References
4 Foundry capabilities for photonic integrated circuits
	4.1 Outline of the ecosystem
	4.2 InP pure play foundries
		4.2.1 InP-specific manufacturing challenges
		4.2.2 State-of-the-art generic InP photonic integrated circuit technologies
			4.2.2.1 Example 1: Fraunhofer HHI
		4.2.3 Multiproject wafer runs
	4.3 Turn-key InP foundry
		4.3.1 State-of-the-art photonic integrated circuit product examples enabled by InP technologies
		4.3.2 InP photonic integrated circuit packaging
		4.3.3 InP photonic integrated circuit manufacturing challenges
		4.3.4 Turn-key photonic integrated circuit foundry
	4.4 Si photonics development
	4.5 Future device integration
		4.5.1 Si- or Ge-based lasers on Si
		4.5.2 III-V-based lasers on Silicon
			4.5.2.1 Heterogeneous bonded lasers
			4.5.2.2 Epitaxially grown lasers
			4.5.2.3 Quantum dot (QD) lasers on silicon
	4.6 Photonics mask making
	4.7 Photonic packaging
		4.7.1 Key photonic integrated circuit packaging technologies
			4.7.1.1 Optical packaging
			4.7.1.2 Fiber edge coupling
			4.7.1.3 Fiber grating coupling
			4.7.1.4 Microoptical coupling
			4.7.1.5 Evanescent coupling
		4.7.2 Electrical packaging
			4.7.2.1 Thermomechanical packaging
		4.7.3 Photonic integrated circuit packaging design rules and standards
	4.8 Silicon photonics integrated circuit process design kit
		4.8.1 Silicon photonics process design kit
			4.8.1.1 Process design kit hierarchy
			4.8.1.2 Development cycle of a process design kit component library
			4.8.1.3 Organization of a process design kit component library
			4.8.1.4 Verification of a process design kit component library
	4.9 Conclusions
	4.10 Disclosure
	Acknowledgments
	References
5 Software tools for integrated photonics
	5.1 The growing need for integration and associated challenges
	5.2 The need to support multiple material systems
	5.3 Applications extend well beyond data communications
	5.4 Challenges specific to photonics
	5.5 The need for an integrated, standard methodology
	5.6 Mixed-mode, mixed-domain simulation
		5.6.1 Physical simulation
		5.6.2 S-parameter-based simulation of photonic circuits
		5.6.3 Transient simulation of photonic circuits
		5.6.4 Sample mode and block mode
		5.6.5 Electro-optical cosimulation
		5.6.6 Dealing with varying timescales
		5.6.7 Electrical, optical, thermal, mechanical
		5.6.8 Circuit and system level
		5.6.9 Other simulation types
	5.7 Photonics layout in electronic design automation
		5.7.1 Photonics layout: curvilinear, non-Manhattan, and extremes of scale
		5.7.2 Schematic driven layout
		5.7.3 The generation, characterization, and simulation of waveguides and connectors
			5.7.3.1 Composite waveguides
			5.7.3.2 Creation/editing
			5.7.3.3 Compose/decompose
			5.7.3.4 Generated connectors
			5.7.3.5 Curved connector
			5.7.3.6 The modal properties of generated waveguides for simulation
			5.7.3.7 Fluid waveguides
	5.8 Electrical and photonic design in the same platform
		5.8.1 A system-level vision
		5.8.2 Thermal impact analysis
		5.8.3 Electromagnetic coupling impact analysis
	5.9 Conclusions
		5.9.1 Today versus the future
		5.9.2 Layout
		5.9.3 Simulation and design: statistical simulation and design for manufacturing
	Acknowledgments
	References
6 Optical processing and manipulation of wavelength division multiplexed signals
	6.1 Introduction
	6.2 Time lenses and phase-sensitive processing
		6.2.1 Fundamentals: principle and potential benefits
			6.2.1.1 Space-time duality
		6.2.2 Flexible spectral manipulation of wavelength division multiplexed signals
			6.2.2.1 K-D-K for spectral compression
			6.2.2.2 Demonstrations of spectral manipulation using time lenses
		6.2.3 Wavelength division multiplexed phase-sensitive regeneration
			6.2.3.1 Principle of wavelength division multiplexed phase regeneration using a time lens and phase-sensitive amplifying unit
			6.2.3.2 Experimental demonstration of simultaneous regeneration of 8 and 16 wavelength division multiplexed differential ph...
				6.2.3.2.1 Experimental results
		6.2.4 Field-quadrature decomposition by polarization-assisted phase-sensitive amplifier
			6.2.4.1 Principle
			6.2.4.2 16-Quadrature amplitude modulation field-quadrature decomposition
		6.2.5 Summary on optical time lenses
	6.3 Optical-phase conjugation
		6.3.1 Fundamentals—principle and potential benefits
		6.3.2 Examples from literature and recent demonstrations
		6.3.3 Coding for the optical-phase conjugation channel: complementary digital and optical signal processing—probabilistic s...
			6.3.3.1 Motivation for the study
			6.3.3.2 Basics of information theory
			6.3.3.3 Algorithm for maximizing the achievable information rate
			6.3.3.4 The optical-phase conjugation case
	6.4 Nonlinear material platforms for optical processing
		6.4.1 Highly nonlinear fiber: Efficiency and limitations
			6.4.1.1 Design and variations
		6.4.2 Photonic chips: broadband and compact
			6.4.2.1 Aluminum gallium arsenide
				6.4.2.1.1 The aluminum gallium arsenide on insulator platform
				6.4.2.1.2 256-Quadrature amplitude modulation wavelength conversion
				6.4.2.1.3 Phase-sensitive four-wave mixing
				6.4.2.1.4 661Tbit/s signal source
				6.4.2.1.5 Summary on aluminum gallium arsenide
			6.4.2.2 Figure of merit of nonlinear materials for optical signal processing
				6.4.2.2.1 Nonlinear figure of merit for nonresonant structures
			6.4.2.3 Amorphous silicon
	6.5 Conclusions
	References
	Further reading
7 Multicore and multimode optical amplifiers for space division multiplexing
	7.1 Introduction
		7.1.1 Cost, space, and energy benefits of space division multiplexing amplifiers
	7.2 Enabling optical components for space division multiplexing amplifiers
		7.2.1 Space division multiplexing components based on micro-optics
		7.2.2 Pump and signal combiners
	7.3 Multicore fiber amplifiers
		7.3.1 Design considerations for multicore fiber amplifiers
		7.3.2 Recent progress in multicore fiber amplifiers
		7.3.3 Fully fiberized 32-core multicore fiber amplifier
	7.4 Multimode fiber amplifiers
		7.4.1 Design concept of multimode fiber amplifiers
		7.4.2 Recent progress in multimode fiber amplifiers
		7.4.3 Fully integrated 6-mode erbium doped fiber amplifier
	7.5 Multimode multicore fiber amplifiers
	7.6 Future prospects
		7.6.1 Current key issues and challenges of space division multiplexing amplifiers
		7.6.2 Potential applications of space division multiplexing amplifier technology
	7.7 Conclusions
	References
Part II: System and Network Technologies
8 Transmission system capacity scaling through space-division multiplexing: a techno-economic perspective
	8.1 Introduction
	8.2 Traffic growth and network capacity scalability options
		8.2.1 Moore’s Law scaling
		8.2.2 High-speed interface scaling
	8.3 Five physical dimensions for capacity scaling
		8.3.1 Increasing capacity through SNR —constraints on M and B
		8.3.2 Power-constrained system scaling—parallelism in M and B
		8.3.3 Bandwidth and space are not created equal
			Reuse of the available infrastructure
			Channel power equalization
			Bandwidth limitations of fiber and system components
			Multiband systems are not truly parallel
			Higher carrier frequencies
			Crosstalk
			Switching
	8.4 Architectural aspects of WDM × SDM systems
		8.4.1 A Matrix of unit cells and their scaling
		8.4.2 Spatial and spectral superchannels
		8.4.3 Array integration and a holistic DSP-electronics-optics co-design
	8.5 Techno-economic trade-offs in WDM × SDM systems
		8.5.1 Chip-to-chip interconnects
		8.5.2 Datacenter interconnects
		8.5.3 Metro and long-haul networking
		8.5.4 Submarine systems
	Acknowledgments
	References
9 High-order modulation formats, constellation design, and digital signal processing for high-speed transmission systems
	9.1 Fiber nonlinearity in optical communication systems with higher order modulation formats
		9.1.1 Introduction to optical fiber nonlinearity
		9.1.2 Nonlinear distortions and modulation dependency
	9.2 Digital schemes for fiber nonlinearity compensation
		9.2.1 Principle of digital backpropagation
		9.2.2 Achievable digital backpropagation gain
	9.3 Digital nonlinearity compensation in presence of laser phase noise
	9.4 Signal design for spectrally efficient optical transmission
		9.4.1 Coded modulation
		9.4.2 Mutual information and generalized mutual information
		9.4.3 Constellation shaping
			9.4.3.1 Probabilistic shaping
			9.4.3.2 Geometrical shaping
		9.4.4 Experimental investigation of high spectral efficiency coded modulation systems for optical communications
			9.4.4.1 Nyquist wavelength-division multiplexing
			9.4.4.2 Higher order modulation formats for the optical fiber channel: experimental and numerical demonstration
			9.4.4.3 Numerical investigation of shaped DP-64QAM and DP-256QAM in the optical fiber channel
	9.5 Conclusions
	Acknowledgments
	References
10 High-capacity direct-detection systems
	10.1 Direct-detection systems and their applications
	10.2 Principle of conventional direct-detection systems
	10.3 Limitations of conventional direct-detection systems
	10.4 Advanced direct-detection systems
		10.4.1 Self-coherent systems: detecting the optical field with a single photodiode
		10.4.2 Kramers–Kronig receivers: rigorous field reconstruction
			10.4.2.1 Principle of operation
			10.4.2.2 Kramers–Kronig receiver-based experimental demonstrations
			10.4.2.3 Discussion
		10.4.3 Stokes vector receivers: polarization recovery without a local oscillator
			10.4.3.1 System architecture
			10.4.3.2 Receiver-side digital signal processing for stokes vector receivers
		10.4.4 Kramers-Kronig Stokes receivers
	10.5 The future of short-reach transmission systems
	References
11 Visible-light communications and light fidelity
	11.1 Introduction
	11.2 An optical wireless communications taxonomy
	11.3 Channel models
		11.3.1 Transmitter model
		11.3.2 Receiver model
		11.3.3 Reflector model
		11.3.4 Channel impulse response
		11.3.5 Existing methods for visible-light communications channel modeling
			11.3.5.1 Deterministic algorithms
			11.3.5.2 Monte Carlo ray-tracing
			11.3.5.3 Analytical methods
		11.3.6 Results of the visible-light communications channel models
	11.4 Analog optical front-end designs
		11.4.1 Transmitter front end
			11.4.1.1 Light-emitting diodes
			11.4.1.2 Laser diodes
		11.4.2 Receiver front end
	11.5 Digital modulation techniques
		11.5.1 Single-carrier modulation schemes
		11.5.2 Multicarrier modulation
	11.6 Multichannel transmission techniques
		11.6.1 Multiple-input multiple-output
		11.6.2 Angular diversity
		11.6.3 Wavelength-division multiplexing
	11.7 Multiuser access techniques
		11.7.1 Optical time division multiple access
		11.7.2 Optical orthogonal frequency division multiple access
		11.7.3 Optical code division multiple access
		11.7.4 Optical space division multiple access
		11.7.5 Power-domain nonorthogonal multiple access
	11.8 Networking techniques for light fidelity
		11.8.1 Network deployment
		11.8.2 Interference mitigation
			11.8.2.1 Joint transmission
			11.8.2.2 Spatial frequency reuse
			11.8.2.3 Busy-burst signaling
		11.8.3 Handover
	11.9 Conclusions
	References
12 R&D advances for quantum communication systems
	12.1 Communication as transfer of information
		12.1.1 Introduction to this chapter
		12.1.2 Information measures
		12.1.3 Channel capacity
	12.2 Quantum physics for communication
		12.2.1 Quantum uncertainty
		12.2.2 Measurement and detectors
		12.2.3 True random numbers generation
		12.2.4 Entanglement and communication
			12.2.4.1 No-signaling theorem
			12.2.4.2 Quantum teleportation
			12.2.4.3 No-cloning theorem
			12.2.4.4 Quantum clock synchronization
			12.2.4.5 The pursuit of superluminal heresy
		12.2.5 Linear quantum amplifier basics
		12.2.6 Quantum state discrimination
			12.2.6.1 Minimum error discrimination
			12.2.6.2 Unambiguous discrimination
		12.2.7 Quantum tomography
	12.3 Quantum mechanics for securing communication channels
		12.3.1 Basic principles of quantum key distribution
			12.3.1.1 Discrete variables quantum key distribution
			12.3.1.2 Continuous variables quantum key distribution
		12.3.2 Eavesdropping challenge
		12.3.3 Channel loss, quantum repeaters, and quantum memory
		12.3.4 Quantum error correction and privacy amplification
	12.4 Modern quantum key distribution
		12.4.1 Fiber-based quantum key distribution
		12.4.2 Free-space quantum key distribution
		12.4.3 Quantum key distribution in satellite communication
	12.5 Quantum supremacy in information processing
		12.5.1 Dense and superdense encoding of information
		12.5.2 Quantum algorithms
		12.5.3 Quantum computing
	Acknowledgments
	References
13 Ultralong-distance undersea transmission systems
	13.1 Undersea transmission over dispersion uncompensated fibers
		13.1.1 Linear and nonlinear degradations in optical fiber
		13.1.2 Gaussian noise model
		13.1.3 Symbol rate optimization
		13.1.4 Nonlinearity compensation
			13.1.4.1 Digital back propagation
			13.1.4.2 Perturbation nonlinearity compensation
			13.1.4.3 Nonlinearity compensation using fast adaptive filters
			13.1.4.4 Other nonlinearity mitigation techniques
			13.1.4.5 Combination of nonlinearity compensation techniques
		13.1.5 Nonlinear transmission optimization
	13.2 Increasing spectral efficiency
		13.2.1 Advanced modulation formats—increasing channel data rate
		13.2.2 Geometric constellation shaping
			13.2.2.1 Probabilistic constellation shaping
			13.2.2.2 Multidimensional coded modulation
			13.2.2.3 Coded modulation with both geometric and probabilistic shaping
		13.2.3 Variable spectral efficiency
			13.2.3.1 Adaptive rate forward error correction
			13.2.3.2 Time-domain hybrid quadrature amplitude modulation
			13.2.3.3 Probabilistic constellation shaping
			13.2.3.4 Coded Modulation
			13.2.3.5 Fine spectral efficiency granularity with coded modulation and adaptive rate forward error correction
	13.3 Increasing optical bandwidth
		13.3.1 Maximizing C-band capacity
		13.3.2 Moving beyond the erbium-doped fiber amplifiers C-band
		13.3.3 Comparison of C+L erbium-doped fiber amplifiers and Raman amplification
		13.3.4 Comparison of C+L erbium-doped fiber amplifier and C+C erbium-doped fiber amplifier
	13.4 Increasing cable capacity
		13.4.1 Space division multiplexing using multicore fiber
		13.4.2 Space division multiplexing using multimode fiber/few-mode fiber/ coupled core multicore fiber
	13.5 Increasing capacity under the constraint of electrical power
		13.5.1 Optimum spectral efficiency
		13.5.2 Optimizing power-efficient undersea systems
		13.5.3 Techniques for power-efficient transmission
		13.5.4 Space division multiplexing technologies in undersea
	13.6 Open cables
		13.6.1 OSNRNL, OSNReff, and GOSNR
		13.6.2 System design trade-offs
	13.7 System value improvements
		13.7.1 Wet wavelength selective switch–based reconfigurable optical add-drop multiplexer
		13.7.2 New cable types: lower cost, higher direct current resistance trade-offs
	13.8 Future trends
	13.9 Conclusions
	Acknowledgments
	List of acronyms
	References
14 Intra-data center interconnects, networking, and architectures
	14.1 Introduction to intra-data center interconnects, networking, and architectures
	14.2 Intra-data center networks
		14.2.1 Data center network growth drivers
		14.2.2 Characteristics and classification of data center networks
			14.2.2.1 Switch-centric topologies
			14.2.2.2 Server-centric and server-switch hybrid topologies
			14.2.2.3 Metrics to compare topologies
		14.2.3 Traffic routing in data center networks
			14.2.3.1 Addressing
			14.2.3.2 Routing and forwarding
		14.2.4 Network cabling
	14.3 Interconnect technologies
		14.3.1 Pluggable form factors
		14.3.2 Direct attach cables (DAC)
		14.3.3 Active optical cables
		14.3.4 Optical transceivers
	14.4 Development of optical transceiver technologies
		14.4.1 40G technologies
		14.4.2 100G technology
		14.4.3 400G technology
	14.5 Future development
		14.5.1 Coherent detection inside data centers
		14.5.2 Mid-board and copackaged optics
		14.5.3 Optical switching inside data centers
	References
15 Innovations in DCI transport networks
	15.1 Introduction
	15.2 Data-center interconnect transport networks
	15.3 Data-center interconnect optimized system
		15.3.1 Requirements and innovations in data-center interconnect systems
		15.3.2 Wavelength-division multiplexing technology building blocks
		15.3.3 Data-center interconnect open line system
	15.4 Emerging data-center interconnect transport innovations
		15.4.1 Software-defined network advancements
			15.4.1.1 Network monitoring
		15.4.2 Optical protection switching
		15.4.3 Data encryption
		15.4.4 Advancements in wavelength-division multiplexing digital signal processing and photonic integration
		15.4.5 Constellation shaping
		15.4.6 L-band, and open line-system disaggregation
		15.4.7 400GE wavelength-division multiplexing ZR
		15.4.8 Implications of intra-data center networking and Moore’s law
	15.5 Outlook
		15.5.1 Power efficient photonics-electronics integration
		15.5.2 Open transport model-driven networking
		15.5.3 Network analytics, optimization, and traffic engineering
		15.5.4 Edge cloud evolution
	Acknowledgments
	References
16 Networking and routing in space-division multiplexed systems
	16.1 Introduction
		16.1.1 Network growth
		16.1.2 Current optical networking
		16.1.3 Wavelength-selective switch optical system
	16.2 Spatial and spectral superchannels
		16.2.1 Spatial parallelism
		16.2.2 Partitioning spatial and wavelength space
		16.2.3 Coupled and uncoupled modes
		16.2.4 Switching and blocking considerations
	16.3 Coupled mode space-division multiplexing
		16.3.1 Multimode switches
		16.3.2 Joint-switching architecture
	16.4 Uncoupled mode space-division multiplexing
		16.4.1 Uncoupled space-division multiplexing fibers
		16.4.2 Transitioning to space-division multiplexing-wavelength-division multiplexed reconfigurable optical add-drop multipl...
		16.4.3 Scaling space-division multiplexing switches
	16.5 Future networks
	16.6 Conclusions
	References
17 Emerging optical communication technologies for 5G
	17.1 Introduction on 5G requirements and 5G-oriented optical networks
		17.1.1 Introduction to 5G requirements
		17.1.2 Introduction on 5G-oriented optical networking
	17.2 Optical interfaces for fronthaul, midhaul, and backhaul
		17.2.1 The partition of fronthaul, midhaul, and backhaul
		17.2.2 The common public radio interface
		17.2.3 The evolved common public radio interface
	17.3 Optical transmission technologies for X-haul
		17.3.1 X-haul via direct fiber connection
		17.3.2 X-haul via passive wavelength-division multiplexing connection
		17.3.3 X-haul via active wavelength-division multiplexing connection
		17.3.4 X-haul via bandwidth-efficient modulation formats
	17.4 5G-oriented optical networks
		17.4.1 Mobile-optimized optical transport network for X-haul
		17.4.2 Advanced coherent transmission for high-performance optical core networks
		17.4.3 Wavelength switching for low-latency optical networks
		17.4.4 Mobile-optimized optical transport network for network slicing
		17.4.5 High-speed low-latency passive optical network for common public radio interface/Ethernet-based common public radio ...
	17.5 Industry standards and development for 5G-oriented optical networks
		17.5.1 5G-oriented optical network architecture and signal structure developments
		17.5.2 5G-oriented optical interface specification developments
		17.5.3 The IEEE Optical Networks 2020 activity
	17.6 Conclusions
	Acknowledgments
	References
18 Optical interconnection networks for high-performance systems
	18.1 Introduction
	18.2 Trends and challenges in computing architecture
		18.2.1 Overview
			18.2.1.1 The end of Moore’s law
			18.2.1.2 Machine learning and data analytics
		18.2.2 High performance computing—toward exascale
			18.2.2.1 The memory bottleneck
			18.2.2.2 Bandwidth steering
		18.2.3 Data centers—scaling and resource utilization
			18.2.3.1 High-bandwidth links in the data center
			18.2.3.2 Resource utilization and disaggregation
	18.3 Energy-efficient links
		18.3.1 Anatomy of optical link architectures
		18.3.2 Comb laser
		18.3.3 Microring-based modulators
		18.3.4 Microring-based drop filters
		18.3.5 Energy-efficient photonic links
	18.4 Bandwidth steering
		18.4.1 Free-space optical switches
		18.4.2 Photonic integrated switches
		18.4.3 Network performance
	18.5 Conclusions
	References
19 Evolution of fiber access networks
	19.1 Introduction
	19.2 Evolution of passive optical networks
		19.2.1 Mature passive optical network standards
			19.2.1.1 Burst mode operation in time-division multiplexing-passive optical networks
			19.2.1.2 Gigabit time-division-multiplexing passive optical network Standards
			19.2.1.3 10Gbps time-division-multiplexing passive optical network Standards
			19.2.1.4 TWDM-passive optical network standards
		19.2.2 Passive optical network standards in the make
			19.2.2.1 IEEE 802.3ca
			19.2.2.2 FSAN and ITU-T SG15/Q2 next-generation passive optical networks
			19.2.2.3 Super-passive optical network
	19.3 Wavelength-division multiplexing and its challenges in access networks
		19.3.1 Wavelength-division multiplexing-passive optical network and wireless fronthaul
		19.3.2 TWDM-passive optical networks and their challenges
	19.4 Enabling technologies on the horizon
		19.4.1 Digital signal processing
		19.4.2 Coherent detection
		19.4.3 Integrated photonics
	19.5 Conclusions
	References
20 Information capacity of optical channels
	20.1 Introduction
	20.2 Information theory
		20.2.1 Discrete-time memoryless channels
			20.2.1.1 The binary symmetric channel
			20.2.1.2 The additive white Gaussian noise channel
		20.2.2 Discrete-time channels with memory
		20.2.3 Mismatched decoding
		20.2.4 Waveform channels
			20.2.4.1 Band-limited channels
			20.2.4.2 The band-limited additive white Gaussian noise channel
	20.3 The optical fiber channel
		20.3.1 The equations governing optical fiber propagation
		20.3.2 The wavelength division multiplexing scenario
		20.3.3 Approximated channel models
			20.3.3.1 The split-step model
			20.3.3.2 The Gaussian noise model
			20.3.3.3 Perturbation methods and the linear time-variant model
	20.4 The capacity of the optical fiber channel
		20.4.1 The linear regime
		20.4.2 The Gaussian achievable information rate and the nonlinear Shannon limit
			20.4.2.1 The Gaussian achievable information rate
			20.4.2.2 Relation to the nonlinear Shannon limit
			20.4.2.3 Dependence on link parameters and configuration
		20.4.3 Improved lower bounds
	20.5 Future perspectives and the quest for an infinite capacity
	Acknowledgments
	References
21 Machine learning methods for optical communication systems and networks
	21.1 Introduction
	21.2 Artificial neural network and support vector machine
		21.2.1 Artificial neural networks
		21.2.2 Choice of activation functions
		21.2.3 Choice of loss functions
		21.2.4 Support vector machines
	21.3 Unsupervised and reinforcement learning
		21.3.1 K-means clustering
		21.3.2 Expectation-maximization algorithm
		21.3.3 Principal component analysis
		21.3.4 Independent component analysis
		21.3.5 Reinforcement learning
	21.4 Deep learning techniques
		21.4.1 Deep learning versus conventional machine learning
		21.4.2 Deep neural networks
		21.4.3 Convolutional neural networks
		21.4.4 Recurrent neural networks
	21.5 Applications of machine learning techniques in optical communications and networking
		21.5.1 Optical performance monitoring
		21.5.2 Fiber nonlinearity compensation
		21.5.3 Proactive fault detection
		21.5.4 Software-defined networking
		21.5.5 Quality of transmission estimation
		21.5.6 Physical layer design
	21.6 Future role of machine learning in optical communications
	21.7 Online resources for machine learning algorithms
	21.8 Conclusions
	Acknowledgments
	References
	Appendix
22 Broadband radio-over-fiber technologies for next-generation wireless systems
	22.1 Introduction on radio-over-fiber
	22.2 Broadband optical millimeter-wave generation
		22.2.1 Basic photonic up-conversion schemes
		22.2.2 Simplified architecture for millimeter -wave generation
	22.3 Broadband millimeter-wave detection in the radio-over-fiber system
	22.4 Digital signal processing for radio-over-fiber systems
		22.4.1 Principle of simplified heterodyne coherent detection based on digital intermediate-frequency down-conversion
		22.4.2 Equalization algorithm of heterodyne coherent detection
			22.4.2.1 Fiber chromatic dispersion compensation
			22.4.2.2 Clock recovery
			22.4.2.3 Polarization demultiplexing and channel dynamic equalization
			22.4.2.4 Carrier recovery
		22.4.3 Digital signal processing for orthogonal-frequency-division-multiplexing millimeter -wave signal detection
			22.4.3.1 Discrete-Fourier-transform spread and intra-symbol frequency-domain averaging
			22.4.3.2 Volterra equalizer in direct detection of orthogonal-frequency-division-multiplexing millimeter -wave signal
	22.5 Broadband millimeter -wave delivery
		22.5.1 Multiple-input multiple-output for millimeter-wave signal delivery
		22.5.2 Multicarrier millimeter -wave signal delivery
			22.5.2.1 Multiband millimeter-wave signal delivery
		22.5.3 Advanced multilevel modulation
	22.6 Long-distance millimeter-wave transmission in the radio-over-fiber system
	22.7 Radio-frequency-transparent photonic demodulation technique applied for radio-over-fiber networks
	22.8 Conclusions
	Acknowledgments
	References
	Further reading
Index
Back Cover