Acknowledgments ................................................ xi
1 Introduction to WDM ........................................ 1
1.1 WDM Theory ................................................. 1
1.2 History of WDM, 2 References ............................... 4
2 Optical Fiber Effects ...................................... 7
2.1 Linear Effects ............................................. 7
2.1.1 Attenuation ......................................... 8
2.1.1.1 Intrinsic Loss ............................. 8
2.1.1.2 Fiber Bending Loss ......................... 9
2.1.1.3 Polarization-Dependent Loss ............... 11
2.1.2 Chromatic Dispersion ............................... 11
2.1.3 Polarization-Mode Dispersion ....................... 16
2.1.3.1 PMD and DGD ............................... 16
2.1.3.2 PMD in Recirculating Loops ................ 23
2.1.3.3 Real-World Fiber Plant PMD Audits ......... 23
2.2 Nonlinear Fiber Effects ................................... 25
2.2.1 Kerr Effects ....................................... 25
2.2.1.1 Self-Phase Modulation ..................... 29
2.2.1.2 Cross-Phase Modulation .................... 34
2.2.1.3 Cross-Polarization Modulation ............. 36
2.2.1.4 Four-Wave Mixing .......................... 37
2.2.1.5 Modulation Instability .................... 43
2.2.1.6 Nonlinear Phase Noise ..................... 43
2.2.2 Scattering Effects ................................. 46
2.2.2.1 Stimulated Raman Scattering ............... 46
2.2.2.2 Brillouin Scattering ...................... 49
References ................................................ 51
3 Components and Subsystems ................................. 55
3.1 Transmitters .............................................. 55
3.1.1 Laser Diodes ....................................... 55
3.1.1.1 Principle of Diode Lasers ................. 55
3.1.1.2 Fabry-Perot Laser Diodes .................. 62
3.1.1.3 Distributed Feedback and Distributed
Bragg Reflector Laser Diodes .............. 63
3.1.1.4 Vertical-Cavity Surface-Emitting Lasers ... 64
3.1.1.5 Tunable Laser Diodes ...................... 64
3.1.2 External Modulators ................................ 70
3.1.2.1 Electroabsorption Modulators .............. 71
3.1.2.2 Electro-Optic Modulators .................. 74
3.1.2.3 Reflective Semiconductor Optical
Amplifiers ................................ 77
3.1.3 Direct-Modulation Techniques ....................... 80
3.1.3.1 Directly Modulated Laser .................. 80
3.1.3.2 Dispersion-Supported Transmission ......... 81
3.1.3.3 Chirp-Managed Laser ....................... 82
3.2 Transmission Line ......................................... 84
3.2.1 Single-Mode Fiber Types ............................ 84
3.2.2 Novel and Specialty Fibers ......................... 87
3.2.2.1 Few-Mode Fibers ........................... 87
3.2.2.2 Multicore Fibers .......................... 88
3.2.2.3 Polymer Optical Fibers .................... 89
3.2.2.4 PCF and PBG Fibers ........................ 89
3.2.3 Fiber-Optic Cables ................................. 91
3.2.4 Optical Amplifiers ................................. 93
3.2.4.1 EDFAs and Other Rare-Earth-Doped Fiber
Amplifiers ................................ 94
3.2.4.2 Raman Amplifiers ......................... 100
3.2.4.3 Semiconductor Optical Amplifiers ......... 101
3.2.5 Dispersion Compensation ........................... 104
3.2.5.1 Dispersion-Compensating Fibers ........... 105
3.2.5.2 Chirped Fiber Gratings ................... 107
3.2.5.3 Self-Phase Modulation (Soliton Effect) ... 109
3.2.5.4 TODC ..................................... 110
3.2.6 Passive WDM Filters and Couplers .................. 111
3.2.6.1 Fused Couplers ........................... 112
3.2.6.2 Thin-Film Filters ........................ 114
3.2.6.3 Arrayed Waveguide Gratings ............... 115
3.2.6.4 Fiber Bragg Gratings ..................... 118
3.2.6.5 Interleaves (Mach-Zehnder
Interferometer) .......................... 119
3.2.6.6 Tunable Filters .......................... 120
3.2.6.7 Wavelength Switching Devices ............. 125
3.2.7 ROADMs and OXCs ................................... 129
3.2.7.1 ROADM Structures ......................... 129
3.2.7.2 Multidegree WSS .......................... 130
3.2.7.3 Optical Cross-Connects ................... 133
3.3 Receivers ................................................ 135
3.3.1 Photodiodes ....................................... 135
3.3.1.1 PIN Photodiodes .......................... 135
3.3.1.2 Avalanche Photodiodes .................... 137
3.3.2 Electronic Amplifiers ............................. 139
3.3.2.1 TIA ...................................... 139
3.3.2.2 Limiting Amplifier ....................... 142
3.3.3 Pluggable Transceivers for WDM .................... 143
3.4 Digital Electronics ...................................... 146
3.4.1 SERDES ............................................ 146
3.4.1.1 Serializer ............................... 147
3.4.1.2 Deserializer ............................. 148
3.4.2 Forward Error Correction .......................... 150
3.4.2.1 FEC Basics ............................... 151
3.4.2.2 Cyclic Codes ............................. 153
3.4.2.3 Code Concatenation and Iterative
Decoding ................................. 155
3.4.3 Electronic Distortion Compensation ................ 158
References ............................................... 162
4 Nonfiber-Related Effects ................................. 177
4.1 Linear Cross Talk ........................................ 177
4.2 Noise in Optical Transmission Systems .................... 181
4.2.1 Noise in Optical Receivers ........................ 182
4.2.2 Receiver Sensitivities ............................ 186
4.2.3 Noise Figures and OSNR in Optical Amplifier
Chains ............................................ 187
References ............................................... 193
5 Modulation Formats For WDM ............................... 197
5.1 Basic Modulation ......................................... 197
5.2 Pulse Shaping ............................................ 202
5.3 Modulation Formats ....................................... 206
5.3.1 Amplitude Modulation .............................. 207
5.3.1.1 On-Off Keying (OOK) ...................... 207
5.3.1.2 Detailed Derivation of OSNR Tolerance
of Directly Detected OOK ................. 209
5.3.1.3 Multilevel Amplitude Modulation .......... 213
5.3.2 Phase Modulation .................................. 215
5.3.2.1 Phase-Shift Keying ....................... 215
5.3.2.2 DPSK with Direct Detection ............... 216
5.3.2.3 (D)XPSK .................................. 218
5.3.3 QAM-Combined Amplitude and Phase Modulation ....... 220
5.3.4 Optical Noise Tolerance of Multilevel Modulation
Formats ........................................... 221
5.3.5 Partial Response Signaling ........................ 224
5.3.5.1 Optical Duobinary ........................ 224
5.3.5.2 Higher Order and Quadrature Partial
Response ................................. 228
5.3.6 Frequency-Shift Keying ............................ 229
5.3.7 Polarization Modulation and Interleaving .......... 230
5.4 Coherent Intradyne Dual-Polarization QAM Detection ....... 231
5.5 Optical OFDM ............................................. 240
5.6 Comparison of Modulation Formats ......................... 243
References ............................................... 247
6 System Realization ....................................... 253
6.1 Access Networks .......................................... 253
6.1.1 CWDM Access and Backhaul .......................... 254
6.1.2 Passive WDM ....................................... 256
6.1.3 PONs and Optical Access Networks .................. 257
6.1.4 WDM-PON ........................................... 259
6.1.4.1 WDM-PON with Tunable Lasers and Laser
Arrays ................................... 261
6.1.4.2 WDM-PON with Seeded Reflective
Transmitters ............................. 266
6.1.4.3 Coherent UDWDM-PON ....................... 271
6.1.5 WDM-Based PON Reach Analysis ...................... 273
6.1.6 WDM-PON Deployment Reference: KT .................. 276
6.2 Corporate Networks (Storage Reach Extensions) ............ 277
6.2.1 Disk Mirroring .................................... 279
6.2.2 Mainframe Coupling/Server Consolidation ........... 281
6.2.3 Low-Latency WDM Transport ......................... 286
6.3 WDM Transport Encryption ................................. 287
6.4 Metro and Regional Networks .............................. 288
6.4.1 DWDM Metro/Regional Ring Networks ................. 288
6.4.2 Capacity in WDM Ring Networks ..................... 291
6.4.3 Wavelength Blocking in WDM Rings .................. 292
6.5 Long-Haul and Ultralong-Haul Systems ..................... 294
6.5.1 Optical Design Challenge .......................... 294
6.5.2 Engineering Models ................................ 295
6.5.2.1 Optical Signal-to-Noise Ratio
Degradation .............................. 296
6.5.2.2 Spectral Ripple and Tilt ................. 296
6.5.2.3 Self-Phase Modulation and Group
Velocity Dispersion ...................... 297
6.5.2.4 Cross-Phase Modulation ................... 298
6.5.2.5 Four-Wave Mixing ......................... 299
6.5.2.6 Stimulated Raman Scattering .............. 299
6.5.3 Link-Based Design Approach ........................ 300
6.5.3.1 Optical Power Management ................. 300
6.5.3.2 Chromatic Dispersion Management .......... 301
6.5.4 Optical-Layer Design Workflow ..................... 302
6.5.5 Mixed 10 Gb/s/100 Gb/s Design ..................... 303
6.5.6 Regional Differences .............................. 306
6.5.7 Terrestrial Long-Haul Deployment Example:
PIONIER ........................................... 307
6.5.8 Submarine Systems ................................. 309
6.5.9 Ultralong-Haul Deployment Example: TAT-14, 312
6.6 Future Network Configurations and Convergence ............ 313
6.6.1 Delayering of Metro Networks ...................... 314
6.6.2 Energy Efficiency of WDM .......................... 315
References ............................................... 321
7 WDM Network Management ................................... 327
7.1 Layered Network .......................................... 327
7.2 Management Approaches .................................... 329
7.3 Basic EMS, NMS, and OSS Functionality .................... 331
7.4 Data Communications Network .............................. 334
7.5 Management System Interfaces ............................. 337
7.6 Control Plane ............................................ 339
7.6.1 Control Plane Interfaces .......................... 340
7.6.2 Migration Scenarios ............................... 341
7.6.3 GMPLS Protocols ................................... 342
7.6.4 Control Plane Mechanisms .......................... 344
7.6.4.1 Automated Network Discovery .............. 344
7.6.4.2 Path Computation ......................... 345
7.6.4.3 Connection Control ....................... 345
7.6.4.4 Resource Management ...................... 347
7.6.4.5 Entity Management ........................ 347
7.6.4.6 Call Control ............................. 347
References ............................................... 348
8 Selected Network Issues .................................. 349
8.1 Overview of the Optical Transport Network ................ 349
8.1.1 OTN Layers ........................................ 349
8.1.2 OTN Mapping and Multiplexing ...................... 351
8.1.3 OTN Operations, Administration, and Monitoring
Aspects ........................................... 354
8.2 Monitoring in WDM Systems ................................ 356
8.2.1 Impairments in Transparent Optical Networks ....... 356
8.2.2 Measurements of the Quality of Optical Signals .... 356
8.2.3 Monitoring Techniques ............................. 358
8.2.3.1 Monitoring Requirements .................. 358
8.2.3.2 CD Monitoring ............................ 359
8.2.3.3 PMD Monitoring ........................... 362
8.2.3.4 OSNR Monitoring .......................... 364
8.2.3.5 Optical Transient Monitoring (OTM) ....... 369
8.2.4 Optical Performance Monitoring .................... 371
8.2.4.1 BER Monitoring ........................... 371
8.2.4.2 Q-Factor Monitoring ...................... 372
8.2.5 Fiber Monitoring .................................. 373
8.3 Flexible WDM Networks .................................... 375
8.4 Protection and Restoration ............................... 377
8.4.1 Dedicated Versus Shared Protection Versus
Restoration ....................................... 377
8.4.2 WDM Protection .................................... 377
8.4.3 WDM-PON Protection ................................ 386
8.4.4 Restoration ....................................... 387
References ............................................... 389
9 Standards Relevant for WDM ............................... 395
9.1 ITU-T Recommendations .................................... 395
9.2 Others ................................................... 396
9.2.1 FSAN (NG-PON2) .................................... 396
9.2.2 OIF ............................................... 397
9.2.3 IEEE-SA ........................................... 397
9.2.4 IETF .............................................. 398
9.2.5 IEC ............................................... 399
9.2.6 Others (INCITS T.11 and IBTA) ..................... 399
10 Practical Approximations and Tips
10.1 Conversion Between Bit Error Rate and Equivalent
Q-Factor ................................................. 401
10.2 Properties of a PRBS Signal .............................. 402
10.3 Chromatic Dispersion Values and Propagation Constants .... 403
References ............................................... 404
Index ......................................................... 405
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