Handbook of optical fibers. Vol. 1

This research- and application-oriented book covers main topical areas of optical fibers. The selection of the chapters is weighted on technological and application-specific topics, very much a reflection of where research is heading to and what researchers are looking for. Chapters are arranged in a user-friendly format essentially self-contained and with extensive cross-references. They are organized in the following sections: - Optical Fiber Communication | Editors: **Ming-Jun Li** and **Chao Lu** - Solitons and Nonlinear Waves in Optical Fibers | Editor: **Boris A. Malomed** - Optical Fiber Fabrication | Editor: **Hairul Azhar Bin Abdul Rashid** - Active Optical Fibers | Editor: **Kyunghwan Oh** - Special Optical Fibers | Editors: **Perry Shum** and **Zhilin Xu** - Optical Fiber Measurement | Editor: **Jianzhong Zhang** - Optical Fiber Devices | Editors: **John Canning** and **Tuan Guo** - Optical Fiber Device Measurement | Editor: **Yanhua Luo** - Distributed Optical Fiber Sensing | Editor: **Yosuke Mizuno** - Optical Fiber Sensors for Industrial Applications | Editor: **Tong Sun OBE** - Polymer Optical Fiber Sensing | Editor: **Ginu Rajan** - Photonic Crystal Fiber Sensing | Editor: **D. N. Wang** - Optical Fiber Microfluidic Sensors | Editor: **Yuan Gong** Preface Contents About the Editor Section Editors Contributors Part I Optical Fiber for Communication 1 Single-Mode Fibers for High Speed and Long-HaulTransmission Introduction Background and History of Optical Fiber History of Fiber Evolution (1966–1987) History of Fiber Evolution (1987–2007) History of Fiber Evolution (2007 Onwards) Optical Fiber Designs for Long-Haul Transmission Quantification of System Level Performance Long-Haul and Ultra-Long-Haul Transmission Systems Raman Gain Considerations Unrepeatered Span Transmission Systems Transmission System Modeling and Experiments Other Factors and Considerations Splice Loss Practical Benefits of Ultra-Low Attenuation and Large Effective Area Fibers Potential Future Directions Conclusions References 2 Multimode Fibers for Data Centers Introduction of Multimode Fibers Basics of Multimode Optical Fibers Light Propagation, Characterization, and Link Performance MMF Characterization: Modal Bandwidth and DMD Source Characterization (Encircled Flux) System Link Models Limitation of VCSEL-MMF Transmission and Novel Solutions Limiting Factors for VCSEL-MMF Transmission Chromatic Dispersion Compensation Performance of MMF with Different Peak Wavelength in WDM-Based Transceivers Modal Dispersion Compensation for SWDM Applications Multimode Fiber for Long Wavelength Applications Motivation for Long Wavelength MMF Systems Design of MMF for Long Wavelength Transceivers System Testing of MMF Optimized for 1060 nm System Testing of MMF Optimized for 1310 nm Universal Fibers, a New Fiber Concept Bridging SM and MM Transmissions in Data Centers Universal Fiber Concept and Benefits Fiber Designs System Level Testing and Verification for Major MM and SM Applications Optical Trends in Data Centers and Concluding Remarks Optical Trends in the Data Center Concluding Remarks References 3 Multi-core Fibers for Space Division Multiplexing Introduction Basics of the Coupled-Mode Theory for Optical Fibers Coupled-Mode Theory for Orthogonal Modes Coupled-Mode Theory for Non-orthogonal Modes Reciprocity of the Mode Coupling Coefficient Uncoupled Multi-core Fibers Mode Coupling in Weakly Coupled MCF Random Mode Coupling Due to Longitudinal Perturbations Discrete Coupling Model and Statistical Distribution of the Crosstalk Coupled Power Theory for Predicting the Statistical Mean of the Crosstalk Local Power Coupling Coefficient Under High-Spatial-Frequency Perturbations Without Bend Radius Change and Fiber Twisting Power Coupling Coefficient Averaged Over Fiber Twisting Crosstalk Suppression Strategy Suppression of the Mode Coupling Coefficient Suppression of the Phase Matching Coupled Multi-core Fibers Systematically Coupled Multi-core Fiber Randomly Coupled Multi-core Fiber Mechanism of Random Mode Coupling Group Delay Spread in Randomly Coupled Multi-core Fiber Common Design Factors for Uncoupled and Coupled Multi-core Fibers Excess Loss Due to the Power Coupling to the Coating Cutoff Wavelength Variation Due to Surrounding Cores Cladding Diameter Conclusion References 4 Optical Coherent Detection and Digital Signal Processing of Channel Impairments Introduction Transmitter Mach-Zehnder Modulator Signal Modulation Analytical Baseband Model Coherent Receiver Optical-to-Electrical Downconversion Single-Polarization Optical-to-Electrical Downconverter Single-Sided Photodetection Heterodyne Detection Dual-Polarization Optical-to-Electrical Downconversion I/Q Imbalance Signal Conditioning Circuit Analytical Baseband Model Emulation of Other Detector Types The Fiber Channel Nonlinear Schrödinger Equation (NLSE) Linear Time-Invariant (LTI) Model Digital Signal Processing Preliminaries Introduction Sampling Rate Requirement Discrete-Time Fourier Transform Linear Equalization Minimum Mean Square Error (MMSE) Equalizer Equalizer Length Requirement MMSE Performance Frequency Domain Equalizer (FDE) Adaptive Time-Domain Equalizer (TDE) Coefficient Update Least Mean Square (LMS) Algorithm Recursive Least Squares (RLS) Algorithm Singularity Problem Adaptive Frequency-Domain Equalizer (FDE) Adaptive Multidelay Block Frequency-Domain Equalizer Hybrid Equalizer Structure Carrier Phase Estimation Laser Phase Noise Phase Estimation in the Absence of Data Modulation Phase Estimation in the Presence of Data Modulation Phase Unwrapping Combining Laser Phase Noise Compensation with Linear Equalization Nonlinear Compensation Digital Backpropagation Split-Step Fourier Method Step-Size Requirement Reduced Complexity Nonlinear Compensation Algorithms Interchannel Nonlinear Compensation Timing Recovery Analog Timing Recovery Digital Timing Recovery Other Topics Space-Division Multiplexing Optical Performance Monitoring Optical Sensing Conclusions References Part II Solitons and Nonlinear Waves in Optical Fibers 5 A Brief History of Fiber-Optic Soliton Transmission Introduction Prehistory of Fiber Solitons: From an Idea to a First Experiment Nonlinear Waves Nonlinear Optics Optical Fiber Technology Toward Experimental Proof of Principle Some Facts About Fibers Some Facts About the NLSE and Its Soliton Solution The Soliton Solution Deviations from the Exact Solution From Lab Curiosity to Commercial Deployment The Soliton Laser The Raman Shift Soliton Interaction Dark Solitons Coding Formats for Optical Telecommunications Generalized NLSE Optical Amplifiers Gordon-Haus Jitter Four-Wave Mixing Dispersion Managed Solitons Commercial Soliton Systems Fiber Solitons in the Twenty-First Century Telecommunications and Limits to Growth Soliton Molecules Soliton Structures on a Background Supercontinuum Generation Rogue Waves Fiber Lasers Beyond the Nonlinear Schrödinger Ansatz Conclusion References 6 Perturbations of Solitons in Optical Fibers Introduction Physical Model and Nonlinear Schrödinger (NLS) Equation Bright and Dark Solitons and the Effect of Perturbations Bright Solitons Dark Solitons Solitons Under Perturbations Bright Solitons Under Perturbations Perturbation Theory for Dark Solitons The Background The Soliton and the Shelf Adiabatic Dynamics Dark Solitons Under Perturbations Beyond the Adiabatic Theory: Soliton Radiation Summary and Conclusions References 7 Emission of Dispersive Waves from Solitons in Axially Varying Optical Fibers Introduction Emission of a Dispersive Wave from a Soliton Fundamental Soliton Dispersive Wave Generation of Dispersive Waves from Solitons in Axially Varying Optical Fibers Axially Varying Optical Fibers Emission of Multiple Dispersive Waves Along the Fiber Cascading of Dispersive Waves Transformation of a Dispersive Wave into a Fundamental Soliton Emission of Polychromatic Dispersive Waves Generation of a Dispersive Wave Continuum Conclusion and Perspectives References 8 Nonlinear Waves in Multimode Fibers Introduction Spatiotemporal Pulse Shaping in Multicore Fibers Pulse Propagation in Multicore Fibers Pulse Compression and Combining Nonlinear Pulses in Multimode Fibers for Spatial-Division Multiplexing Spatial-Division Multiplexing Nonlinear Propagation in Multimode Fibers The Influence of Nonlinear Effects on the Propagation of Optical Signals Raman Cleanup Effect and Raman Lasing in Multimode Graded-Index Fibers Experimental Observations and Theoretical Models of Raman Cleanup Effect Raman Cleanup Effect in Raman Fiber Amplifiers and Lasers GRIN Fiber Raman Lasers Directly Pumped by Multimode Laser Diodes Combined Action of Raman Beam Cleanup and Mode-Selecting FBGs in GRIN Fiber Raman Lasers Kerr Beam Self-Cleaning Theoretical Models of Spatiotemporal Dynamics Kerr Beam Cleanup in GRIN MMF Kerr Beam Cleanup in Step-Index Active MMF with Loss or Gain Self-Cleaning in a MMF Laser Cavity References 9 Shock Waves Introduction Gradient Catastrophe and Classical Shock Waves Regularization Mechanisms Shock Formation in Optical Fibers Mechanisms of Wave-Breaking in the Normal GVD Regime Shock in Multiple Four-Wave Mixing The Focusing Singularity Control of DSW and Hopf Dynamics Riemann Problem and Dam Breaking Competing Wave-Breaking Mechanisms Resonant Radiation Emitted by Dispersive Shocks Phase-Matching Condition Steplike Pulses Bright Pulses Periodic Input Shock Waves in Passive Cavities Conclusions Appendix A References 10 A Variety of Dynamical Settings in Dual-CoreNonlinear Fibers The List of Acronyms Introduction Solitons in Dual-Core Fibers The Symmetry-Breaking Bifurcation (SBB) of Solitons The Formulation of the Model Continuous-Wave (CW) States and Their Modulational Instability (MI) The Variational Approximation (VA) for Solitons Gap Solitons in Asymmetric Dual-Core Fibers The Coupler with Separated Nonlinearity and Dispersion Two Polarizations of Light in the Dual-Core Fiber Solitons in Linearly Coupled Fiber Bragg Gratings (BGs) Bifurcation Loops for Solitons in Couplers with the Cubic-Quintic (CQ) Nonlinearity Dissipative Solitons in Dual-Core Fiber Lasers Introduction The Exact SP (Solitary-Pulse) Solution Special Cases of Stable SPs (Solitary Pulses) Stability of the Solitary Pulses and Dynamical Effects Interactions Between Solitary Pulses CW (Continuous-Wave) States and Dark Solitons (``Holes'') Evolution of Solitary Pulses Beyond the Onset of Instability Soliton Stability in PT (Parity-Time)-Symmetric Nonlinear Dual-Core Fibers Conclusion References Part III Optical Fiber Fabrication 11 Advanced Nano-engineered Glass-Based Optical Fibers for Photonics Applications Introduction Importance of the Nano-engineered Glass-Based Optical Fiber The Basic Material of Nano-engineered Glass-Based Optical Fiber Importance of Ceramic Oxides in Nano-engineered Glass-Based Optical Fiber Mechanism to Develop Nano-engineered Glass-Based Optical Fiber Fiber Drawing Process Fabrication of Erbium-Doped Nano-engineered Zirconia-Yttria-Alumina-Phospho-Silica (ZYAPS) Glass-Based Optical Fiber Material Characterization of Erbium-Doped Nano-engineered ZYAPS Glass-Based Optical Preform and Fiber The Optical Performance of Erbium-Doped Nano-engineered ZYAPS Glass-Based Optical Fiber Fabrication of Erbium-Doped Nano-engineered Scandium-Phospho-Yttria-Alumina-Silica (SPYAS) Glass-Based Optical Fiber Material Characterization of Erbium-Doped Nano-engineered SPYAS Glass-Based Optical Preform and Fiber The Optical Performance of Erbium-Doped Nano-engineered SPYAS Glass-Based Optical Fiber Fabrication of Multielement (P-Yb-Zr-Ce-Al-Ca) Fiber for Moderate-Power Laser Application Material Characterization of Multielement (P-Yb-Zr-Ce-Al-Ca) Optical Preform and Fiber The Optical Performance of Multielement (P-Yb-Zr-Ce-Al-Ca) Optical Fiber Fabrication of Chromium-Doped Nano-phase Separated Yttria-Alumina-Silica (YAS) Glass-Based Optical Fiber Material Characterization of Chromium-Doped Nano-phase Separated YAS Glass-Based Optical Preform and Fiber The Optical Performance of Chromium-Doped Nano-phase Separated YAS Glass-Based Optical Fiber Conclusions Future Work References 12 Fabrication of Negative Curvature Hollow Core Fiber From Conventional Fibers to Photonics Crystal Fibers Photonic Crystal Fiber Background of Photonics Crystal Fiber Development of Hollow Core Fiber Development of Negative Curvature Hollow Core Fibers The Importance Negative Curvature Guiding Mechanism Antiresonant Reflecting Optical Waveguide (ARROW) Marcatili and Schmeltzer's Model Coupled-Mode Model Fabrication of Fiber Fabrication of Negative Curvature Hollow Core Fiber Stack and Draw Stack Drawing of Cane Drawing of Fiber Design and Properties of Fiber Fiber Design Attenuation Measurement: Cutback Method Conclusion References 13 Optimized Fabrication of Thulium Doped Silica Optical Fiber Using MCVD Introduction Thulium Doped Fibers Fabrication Methods of Silica Fibers MCVD-Solution Doping Technique Fabrication and Characterization of Optical Fiber Preforms Soot Deposition Temperature Mechanism of Soot Deposition Soot Characteristics: Physisorption and Scanning Electron Microscope (SEM) Measurements Effect of Soot Condition on the Final Preform Characteristics Alumina, Gallia, and Baria Solution Doped Silica Preforms Aluminum Doped Preforms Gallium Doped Preforms Barium Doped Preforms Spectroscopic Characteristics of Thulium Doped Fibers (TDF) Absorption Lifetime Conclusions References 14 Microfiber: Physics and Fabrication Introduction Principle Wave Equation for Microfiber Adiabaticity Criterion Fabrication Techniques Fabrications of Meso Taper The MT Shape and the Design of Fabrication System Fabrications of Short Taper Flame-Brushing Technique Modified Flame-Brushing Technique Self-Modulated Taper-Drawing Technique Direct Drawing from Bulk Technique Comparison of Short Taper Fabrication Techniques Fabrications of Long Taper Application in Structural Health Monitoring Microfiber-Based IMZI Sensor Packaging Microfiber-Based IMZI Sensor Deployment Summary References 15 Flat Fibers: Fabrication and Modal Characterization Introduction Flat Fiber Fabrication Flat Fiber Drawing Repeatability Flat Fibers with Different Dimensions Characterization of Flat Fibers: Mode Propagation Multimode Propagation in Flat Fibers Single-Mode Propagation in Flat Fibers Conclusion References 16 3D Silica Lithography for Future Optical Fiber Fabrication Introduction Conventional Silica fiber Fabrication 3D Silica fiber Fabrication 3D Fabrication (3D Printing) 3D silica lithography 3D Silica fiber Fabrication Challenges and Pathways to 3D Silica fiber Fabrication Challenges for 3D Silica fibers Pathways for 3D Silica fibers Initial Results Conclusion References Part IV Active Optical Fibers 17 Rare-Earth-Doped Laser Fiber Fabrication Using Vapor Deposition Technique Introduction Preform Technologies MCVD Process Combined with Solution Doping for Rare-Earth and Aluminum Incorporation Refractive Index and Diffusion Properties of RE-Doped Fibers Background Losses in RE-Doped Fibers Absorption and Emission Properties of RE-Doped Fibers Photodarkening MCVD Process Combined with Gas Phase Doping for Rare-Earth and Aluminum Incorporation Refractive Index Behavior and Concentration Distribution Incorporation of Yb and Al into Silica via Gas Phase Absorption and Emission Properties of the Preforms and Fibers Laser Behavior of the Fibers Conclusion References 18 Powder Process for Fabrication of Rare Earth-Doped Fibers for Lasers and Amplifiers Introduction Optical Glass and Fibers Modern Optical Fibers Technological Changes in Optical Glass Fiber Production Techniques Chemical Vapor Deposition (CVD) Modified Chemical Vapor Deposition (MCVD) Production of Active Fibers by Rare Earth Activation Rediscovering Powder Techniques for Fiber Production Powder Technologies for Fiber Production Powder-in-Tube (PIT) Improving Homogeneity Refractive Index Control by Simultaneous Addition of Al2O3 and P2O5 Producing the Core Material Outside of the Preform Core Material Production by Suspension Doping of Fine Silica Powder: REPUSIL General Granulate Considerations Granulated Silica Powder-in-Tube (PIT) Technique Doping Concentration Granulated Silica Material Production: The Oxides Approach Powder Synthesis by Mixing Oxides Post-Processing: Oxides Derived Granulate Iterative Vitrification and Fine Milling Coarse Crushing and Sieving Fibers Based on the Oxides Approach Granulated Silica Material Production: The Sol-Gel Approach Powder Synthesis Using the Sol-Gel Process Post-Processing: Sol-Gel-Derived Granulate Drying into Powder (Low Temp Range) Fine Milling and Sintering Coarse Crushing and Sieving Additional Vitrification of Thin Powder-in-Tube Preform Fibers Based on the Sol-Gel Approach Solubility and Homogeneity of Rare Earth Elements Thermodynamic Properties of Rare Earth Ion-Doped Silica Powder (Tg, Tx, Tc) References 19 Progress in Mid-infrared Fiber Source Development Introduction Background on Lasers in the Mid-IR Carbon Dioxide and Monoxide Lasers Solid-State Lasers Based on Cr:ZnSe/S Optical Parametric Amplifiers and Oscillators Optical Parametric Chirped-Pulse Amplifiers Mid-IR Fiber Lasers: Overviews and Challenges Fibers and Glasses for the Mid-IR Silicates Fluorides Chalcogenides Spectroscopy of the Significant Rare-Earth Transitions Used for Mid-IR Fiber Lasers Spectroscopy and Lasing of Er3+ Ion Spectroscopy and Lasing of Ho3+ Ion Mid-IR Fiber Laser Architectures Single-Longitudinal-Mode Systems High-Power cw Systems Tunable cw Systems Ultrafast Systems Supercontinuum Generated in Mid-IR Transparent Fibers Supercontinuum Generated via Optical Parametric Amplification Systems Supercontinuum Generation via Near-IR Fiber Laser Pumping Supercontinuum Generation via Diode Lasers Supercontinuum Generation via Mid-IR Fiber Laser Pumping Conclusion References 20 Crystalline Fibers for Fiber Lasers and Amplifiers Introduction Crystalline Fiber Core The LHPG Method The Growth Mechanism Crystal Fiber Host and Dopant Characterization Glass Cladding The Co-drawing LHPG Method The Residual Strain in Glass-Clad Crystalline Fiber Crystalline Core and Glass Clad Interface Light Transmission Characteristics Crystalline Fiber-Based Broadband Spontaneous Emission Ce:YAG as Crystalline Core Ti:sapphire as Crystalline Core Cr:YAG as Crystalline Core Crystalline Fiber Laser and Amplifier Tunable Cr4+:YAG Crystalline Fiber Laser Wavelength Tuning by Pellicle Etalon Wavelength Tuning by Diffraction Grating Wavelength Tuning by Birefringent Filter Crystalline Fiber Amplifier Conclusion References 21 Cladding-Pumped Multicore Fiber Amplifier for Space Division Multiplexing Introduction Multicore Fiber Amplifier Multicore Erbium-Doped Fiber Signal/Pump Coupler for MCFA Pump Dump Cross Talk Among the Spatial Channels Numerical Simulation Gain and NF of Cladding-Pumped MC-EDFA Effect of Enlarging the Core Size Cross-Gain Modulation Due to Gain Depletion Power Conversion Efficiency Experimental Demonstration of Cladding-Pumped Multicore Fiber Amplifiers Cladding-Pumped MC-EDFA with End Pumping Cladding-Pumped MC-EDFA Employing Side-Coupled Pumping Experimental Results End-Coupled Pumping Side-Coupled Pumping Comparison Between Core- and Cladding-Pumped Amplifiers Electrical Power Consumption Recent Advancements Summary References 22 Optical Amplifiers for Mode Division Multiplexing Introduction Current State of the Art in SDM Amplifiers SDM Optical Components Fiber-Optic Collimator Assembly Pump Coupler Mode-Field Diameter Adaptor Mode-Dependent Loss Equalizer Design of Few-Mode Fiber Amplifiers The Importance of Differential Modal Gain (DMG) Control Design Strategies for Reducing DMG of FM-EDFAs Controlling the Transverse Pump Field Distribution Tailoring the Radial Dopant Distribution of the Active Fiber Engineering the Signal Mode Profiles Other Approaches Core-Pumped 6-Mode EDFA Cladding-Pumped 6-Mode EDFA Challenges and Future Development Conclusion References Part V Special Optical Fibers 23 Optical Fibers for High-Power Lasers Introduction Passive Fibers for High-Power Laser Beam Delivery Active Fibers for High-Power Laser Beam Generation Specialty Fibers for High-Power Lasers Double-Cladding Fibers Large Mode Area Photonic Crystal Fibers Large Pitch Fibers Leakage Channel Fibers Chirally Coupled Core Fibers Pixelated Bragg Fibers Hollow-Core Fibers Conclusion References 24 Multicore Fibers Introduction The Necessity of Space Division Multiplexing Technology Classification of SDM Research Progress of SDM Based on MCF MCF Design and Fabrication Uncoupled-Core MCF Coupled-Core MCF FM-MCF Fan-In and Fan-Out Splicing Technology for MCF Erbium-Doped Fiber Amplifier for MCF Core Pumped MC-EDFA Cladding-Pumped MC-EDFA MCF-Based Communication Systems MCF-Based Optical Access Network MCF-Based Front-Haul MCF-Based Short-Reach Interconnect MCF-Based Long-Haul Transmission MCF-Based Optical Sensing Systems Discrete MCF Sensing Technology Distributed MCF Sensing Technology Conclusion References 25 Polymer Optical Fibers Introduction Development of POF Key Features of POF Materials for POF Types of POF SI-MM POF GI-MM POF SM POF EO POF Segmented Cladding POF Scintillating POF Dye-Doped POF Photorefractive POF Photosensitive POF Microstructured POF POF Fabrication Techniques Extrusion Method Extrusion of SI-POF Extrusion of SI-MPOF Extrusion of GI-POF Preform Method SI-POF Preform Fabrication GI-POF Preform Fabrication 3D Printing Method POF for Data Transmission POF for Sensing Radiation Detection Biomedical and Chemical Sensor Structural Health Monitoring Cracking Detection Environment Monitoring Humidity Sensor Dew-Point Sensor Oxygen Sensor Dangerous Gas Sensor Single-Mode POF Sensors and Applications POF for Illumination Final Remarks References 26 Optical Fibers in Terahertz Domain Introduction Constraints and Challenges for Developing THz Fibers Solid-Core THz Fibers Sub-wavelength Diameter Fibers Porous Fibers Solid-Core Photonic Crystal Fibers Hollow-Core THz Fibers Dielectric-/Metal-Coated Hollow-Core Fibers Hollow-Core Bragg Fibers Hollow-Core Pipe Fibers Kagome Hollow-Core Photonic Crystal Fibers Tube Lattice Hollow-Core Fibers Conclusion References 27 Optical Fibers for Biomedical Applications Introduction Basic Concepts of Optical Fibers Light-Guiding Principles in Conventional Fibers Ray Optics Concepts Modal Concepts Graded-Index Optical Fibers Core Index Structure Graded-Index Numerical Aperture Cutoff Wavelength in Graded-Index Fibers Performance Characteristics of Generic Optical Fibers Attenuation Versus Wavelength Bend-Loss Insensitivity Mechanical Properties Optical Power-Handling Capability Optical Fibers Used in Biophotonics Conventional Solid-Core Fibers Specialty Solid-Core Fibers Photosensitive Optical Fiber Fibers Resistant to UV-Induced Darkening Bend-Insensitive Fiber Polarization-Maintaining Fibers Double-Clad Fibers Hard-Clad Silica Fibers Coated Hollow-Core Fibers Photonic Crystal Fibers Plastic Fibers Side-Emitting or Glowing Fibers Middle-Infrared Fibers Optical Fiber Bundles References Part VI Optical Fiber Measurement 28 Basics of Optical Fiber Measurements Introduction Optical Fiber Basics Basics of Optical Fiber Basic Parameters and Definitions Acceptance Angle and Numerical Aperture Attenuation Coefficient Cut-Off Wavelength Mode Field Diameter and Spot Size Components and Test Equipment Components and Handling Techniques Light Source Photodetector Cables and Connectors Fiber Handling Test Tools and Equipment Splicer and Cleaver Optical Power Meter Optical Spectrum Analyzer Attenuation Measurements Spectral Attenuation Measurement Insertion Loss Measurement Optical Time Domain Reflectometer Loss Measurement Index Profile and Geometry Measurement Fiber Design Parameters Cut-Off Wavelength Measurement Spot Size Measurement Geometry Refractive Index Profiling Interference Microscopy Method Focusing Method and Ray Tracing Method Light Scattering Method and Reflection Method Digital Holographic Microscopy Method References 29 Measurement of Active Optical Fibers Introduction Basics of Active Optical Fibers Interaction Between Light and Matter Einstein Relation Light Absorption and Gain The Absorption and the Emission Cross Sections Lifetime Typical Active Ions and Properties Energy Level System of Er3+ Ion-Ion Interactions Excited State Absorption (ESA) Up-conversion Emission Measurement of Absorption Ground State Absorption Measurement Cut-Back Method Pump Absorption Definitions Measurement Measurement of Emission Measurement of Spectral Emission Forward Emission Backward Emission Axial Emission by Side Pumping Combined Excitation-Emission Spectroscopy Measurement of Fluorescent Lifetime Time Domain Frequency Domain Measurement of Gain Principle of Gain Measurement Gain Measurement References 30 Characterization of Specialty Fibers Introduction Dispersion Characterization of Optical Fibers Dispersion Characteristics Chromatic Dispersion Material Dispersion Waveguide Dispersion Intermodal Dispersion Polarization Mode Dispersion Dispersion Measurement Chromatic Dispersion Measurement Phase Shift Method AM Response Method Intermodal Dispersion Measurement Time Domain Measurement Frequency Domain Measurement Polarization Characterization of Optical Fibers State of Polarization (SOP) Birefringence and Beat Length Polarization Mode Dispersion (PMD) PMD Measurement Pulse Delay Method Interferometric Method Poincare Arc Method Jones Matrix Method Mueller Matrix Method Polarization-Dependent Loss (PDL) Special Characterization Techniques Material Characterization Physical Analysis of Active Fiber Chemical Analysis of Active Fiber Spectral Characterization Absorption and Emission Measurement Absorption Spectrum Measurement Based Absorption and Emission Spectra Measurement Based on Side Pumping Method Conclusion References 31 Characterization of Distributed Birefringencein Optical Fibers Introduction Operation Principle of BDG Theoretical Analysis of BDG Principle of Generation and Detection of BDG Phase Matching Condition Coupled Wave Equations of the Brillouin-Enhanced FWM Process Characteristics of the BDG Reflection Spectrum Distributed Birefringence Measurement of PMFs and Its Sensing Applications Numerical Calculations of the Birefringence Distributed Phase Birefringence Measurement of the PMFs with BDGs Experimental Measurement for Different PMFs Extension of the Measurement Range Sensing Applications Distributed Temperature and Strain Measurement Distributed Transverse Pressure Measurement Distributed Hydrostatic Pressure Measurement Conclusion References 32 Characterization of Distributed Polarization-Mode Coupling for Fiber Coils Introduction Measurement and Analysis for Distributed Polarization Crosstalk Distributed Polarization Crosstalk Optical Coherence Domain Polarimetry System Jones Matrix Method Optical Path Tracking Method Stable Unit and Recursion Formula Classifications and General Formulas Range Extension of Optical Delay Line for OCDP System Principle of Operation Device, Implementation, and Performance Measurement Uncertainties The Precise Identification σA of the Zero-Order Fringe Temperature Instability σB The Measurement Accuracy σC of the Scanning Stage Accuracy Improvement of Optical Delay Line for OCDP System Distributed Polarization Crosstalk Measurement with Loss Coefficient Differential Delay Line Structure Measurement with Differential Structure Delay Line Iterative Dispersion Compensation for Measuring PMF Birefringence Dispersion of PMF Iterative Dispersion Compensation Method High-Resolution Measurement Cancelling Dispersion PMF Coil Diagnosis Analysis Method of PMF Coil Data Diagnosis Results of PMF Coil PMF Coil Floor Periodicity of PMF Coil Diagnosis Results at Different Temperatures Conclusion References Part VII Optical Fiber Devices 33 Materials Development for Advanced Optical Fiber Sensors and Lasers Introduction The Materials Science of Optical Nonlinearities The Nonlinearities Stimulated Brillouin Scattering (SBS) Stimulated Raman Scattering (SRS) Transverse Mode Instability (TMI) n2-Related Effects Materials Modeling Modeling the Fiber Structure Applications of Intrinsically Low Nonlinearity Materials Passive Fibers Active Fibers Lidar Lidar, Prospects, and Future Directions Fiber-Based High-Energy Lasers (HEL) Prospects and Future Directions Applications in the Other Direction: Larger Nonlinearities Distributed Fiber Sensing Prospects and Future Directions Notes on Fiber Fabrication Conclusion References 34 Optoelectronic Fibers Introduction Material Selection Silicon Germanium Compound Semiconductors Fabrication Approaches Thermal Drawing High-Pressure Chemical Vapor Deposition Post-processing Selective Breakup Conclusions and Outlook References 35 Fiber Grating Devices Introduction Near-Infrared SPP Excitation with Gold-Coated TFBGs Operating Principle of TFBG Refractometers Influence of the Tilt Angle on the Transmitted Amplitude Spectral Content TFBGs Fabrication Gold Deposition on the Optical Fiber Surface Surface Functionalization Interrogation of Gold-Coated TFBG Immunosensors Proteins and Cells Quantification with Gold-Coated TFBG Immunosensors Sensing Density Alteration in Cells Sensing Cytokeratins Sensing Transmembrane Receptors Sensing Electroactive Biofilms Conclusion References 36 CO2-Laser-Inscribed Long Period Fiber Gratings: From Fabrication to Applications Introduction CO2 Laser Inscription Techniques LPFG Inscription in Conventional Glass Fibers LPFG Inscription in Solid-Core PCFs LPFG Inscription in Air-Core PBFs Grating Formation Mechanisms Refractive Index Modulations Residual Stress Relaxation Glass Structure Change Physical Deformation Asymmetrical Mode Coupling Improvements of Grating Fabrications Pretreatment Techniques Hydrogen Loading Applying Prestrain Posttreatment Techniques Applying Tensile Strain Changing Temperature Sensing Applications Temperature Sensors Strain Sensors Bend Sensors Torsion Sensors Pressure Sensors Biochemical Sensors Communication Applications Band-Rejection Filters Gain Equalizers Polarizers Couplers Mode Converters Conclusions References 37 Micro-/Nano-optical Fiber Devices Introduction Manufacture of MNOFs Fabrication of MNOFs by Top-Down Techniques Manufacture of MNOF Tips by a Pipette Puller Embedding The Shape of Fiber Taper Linear and Nonlinear Characteristic Properties of MNOFs Basic Waveguide Theory Dispersion and Nonlinearity Post-processing Techniques Micromachining Techniques Wrap-on-a-Rod Surface Functionalization with External Materials Two-Dimensional Material Integration Passive and Active Devices Grating Coupler Interferometers Highly Birefringent MNOF Graphene-Integrated Devices Sensing Applications Fluidic Applications Conclusion References Part VIII Optical Fiber Device Measurement 38 Measurement of Optical Fiber Grating Introduction Fiber Grating Development Photosensitive Fiber Fiber Grating Types Classification Based on Grating Structure Classification Based on Grating Fabrication Mechanism Classification Based on Fiber Materials Fiber Grating Fabrication Fiber Grating Measurement Measurement of Fiber Grating Structural Parameters Measurement of F