Troubleshooting optical-fiber networks: understanding and using your optical time-domain reflectometer

Duwayne R. Anderson, Larry M. Johnson, Florian G. Bell9780120586615, 0120586614

The fiber optic equipment market will grow to over $24 billion in 2004. Careful assessment of critical networks is made easier with the use of an optical time-domain reflectometer (OTDR), which measures the elapsed time and intensity of light reflected along an optical fiber. They are useful tools for locating problems in an optical network as they can compute the distance to breaks or attenuation. The accuracy and power of modern OTDRs often exceeds the skill of the operator using it! This book offers comprehensive, state-of-the-art information about time-domain fiber-optic testing. Readers will gain an understanding of how to troubleshoot optical-fiber networks using an OTDR, while learning the fundamental principles underlying the operation of these powerful testing instruments. From basic fiber optics and fiber testing, to detailed event-analysis techniques, this book covers the entire spectrum of time-domain optical cable test theory.

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Table of contents :
Team DDU……Page 1
Contents……Page 6
Foreword……Page 12
1 0 Introduction……Page 16
1 1 The birth of the OTDR……Page 17
1 2 Features, functions, and performance improvements……Page 19
1 3 Summary……Page 24
Suggested reading……Page 26
2 1 Total internal refl ection……Page 28
2 2 Fiber attenuation……Page 34
2 3 Numerical aperture……Page 38
2 4 Multipath (modal) dispersion……Page 39
2 5 Chromatic dispersion……Page 43
2 6 Wavelength-division-multiplexed systems……Page 50
2 7 V-parameter, cut-off wavelength, and spot profi le……Page 51
2 8 Splices and connectors……Page 57
2 9 Bending loss……Page 63
2 10 Coherence……Page 67
2 11 Summary……Page 70
Problems……Page 72
3 0 Introduction……Page 74
3 1 OTDR design……Page 77
3 2 A typical OTDR waveform……Page 78
3 3 Multiple-wavelength OTDRs……Page 80
3 4 Optical masking……Page 82
3 5 Evolution of the OTDR……Page 84
3 6 Rayleigh backscatter……Page 87
3 7 Dynamic range……Page 89
3 8 Differences between multimode and single-mode OTDRs……Page 93
3 8 2 Refl ectivity differences between single-mode and multimode fi ber connectors……Page 96
3 8 3 Differences in backscatter levels……Page 97
3 8 5 Pulse-width differences……Page 98
3 8 6 Operating-wavelength differences……Page 99
3 9 Echoes and ghosts……Page 102
3 10 1 Standard OTDR with an EDFA……Page 106
3 10 2 Coherent-detection OTDR……Page 108
3 10 3 Correlation OTDR……Page 110
3 10 4 Short-coherence-length coherent OTDRs (multimode)……Page 111
3 10 5 Photon-counting OTDRs……Page 113
3 11 Summary……Page 114
Suggested reading……Page 115
Problems……Page 116
4 1 Figures of merit……Page 118
4 2 Historical fi gures of merit……Page 120
4 3 Detailed fi gures of merit……Page 122
4 3 1 Refl ective dynamic range……Page 123
4 3 2 Scattering dynamic range……Page 124
4 3 3 Derivation of the noise fl oor……Page 130
4 3 4 Dynamic-range margin……Page 136
4 3 5 Usable dynamic range……Page 138
4 3 6 Measurement range……Page 139
4 3 7 How offset errors affect dynamic-range and measurement-range calculations……Page 140
4 3 8 Event resolution……Page 150
4 3 9 Loss-measurement resolution……Page 152
4 3 10 Return loss……Page 154
4 3 11 Linearity……Page 155
4 3 12 Data resolution……Page 156
4 3 13 Clock accuracy……Page 158
4 3 15 Refractive-index uncertainty……Page 159
4 3 16 1 Fiber length……Page 161
4 3 16 3 Data-processing speed……Page 162
4 3 17 Event-detection accuracy……Page 163
4 4 Standards……Page 164
4 5 Summary……Page 165
Problems……Page 166
5 1 Sources of nonrefl ective events……Page 168
5 2 Cursor placement for manual loss and distance measurements……Page 171
5 3 1 Distance-measurement errors caused by waveform noise……Page 173
5 3 2 Distance-measurement errors caused by fi ltering……Page 182
5 3 3 Other contributions to distance-measurement errors……Page 185
5 4 Summary……Page 191
Suggested reading……Page 192
Problems……Page 193
6 1 Loss-measurement errors caused by waveform noise……Page 194
6 2 Loss-measurement errors due to mismatch of single-mode fi bers……Page 200
6 3 Loss-measurement errors on multimode fi ber……Page 205
6 4 Bending loss and stress loss in single-mode fi bers……Page 211
6 5 Wavelength-dependent loss in fusion splices and connectors between single-mode fi bers……Page 213
6 6 Intrinsic loss in single-mode fusion splices……Page 215
6 7 Summary……Page 220
Problems……Page 221
7 1 Background……Page 224
7 2 1 Refl ections from angled cleaves……Page 227
7 2 2 Refl ections from connectors……Page 229
7 2 3 Refl ections from mechanical splices……Page 235
7 3 Measuring refl ective events using an OTDR……Page 236
7 4 Effects that can reduce the accuracy of refl ectivity measurements……Page 241
7 5 Calibrating the OTDR’s backscatter coeffi cient……Page 244
7 5 1 Calculating the backscatter coeffi cient……Page 245
7 5 2 1 Measuring the backscatter coeffi cient with a calibrated refl ector……Page 248
7 5 2 2 Measuring the backscatter coeffi cient using a CWR……Page 250
7 5 2 3 Measuring the backscatter coeffi cient using an OTDR……Page 252
7 6 Integrated return loss……Page 255
7 7 Summary……Page 260
Problems……Page 262
8 1 Refl ections and the dead zone……Page 264
8 2 Improving the dead zone by optical masking……Page 267
8 3 Impact of refl ections on transmitters and receivers……Page 272
8 4 Dead zone box……Page 278
Problems……Page 280
9 0 Introduction……Page 282
9 1 The far-fi eld scanning method of determining numerical aperture……Page 283
9 2 Measuring the numerical aperture of single-mode fi ber using an OTDR……Page 287
9 3 Measuring the cut-off wavelength of a single-mode fi ber using an OTDR……Page 290
Suggested reading……Page 292
Problems……Page 293
10 0 Introduction……Page 294
10 1 Determining the locations of breaks in systems containing splitters……Page 299
10 2 OTDR requirements for testing networks with splitters……Page 302
Suggested reading……Page 304
Problems……Page 305
11 1 Types of event markings……Page 306
11 2 Functionality of different types of event markings……Page 308
11 3 Optimizing acquisition parameters……Page 313
11 4 Measuring individual events……Page 319
11 5 1 Test-fi ber calibration……Page 327
11 5 2 Repeatability testing……Page 329
11 6 Event-marking features……Page 332
11 7 Remote OTDRs for monitoring networks……Page 336
11 8 Summary……Page 340
Suggested reading……Page 341
Problems……Page 342
12 1 Dead zone fi xture……Page 344
12 2 Fiber circulator……Page 345
12 3 External-source test fi xture……Page 352
12 4 Loss calibration with fi ber standard……Page 353
12 5 Summary……Page 355
Suggested reading……Page 356
Problems……Page 357
13 0 Introduction……Page 358
13 1 Measurement techniques……Page 361
13 2 PMD model of optical fi ber……Page 364
13 3 Mathematical model of a polarization OTDR……Page 368
13 4 Summary……Page 372
Problems……Page 373
14 0 Introduction……Page 374
14 1 Intermodal dispersion……Page 376
14 2 1 Material dispersion……Page 379
14 2 2 Waveguide dispersion……Page 381
14 3 Dispersion reduction in optical fi bers……Page 383
14 4 Measuring dispersion using an OTDR……Page 384
14 5 Measuring chromatic dispersion using multiple-wavelength OTDRs……Page 387
14 6 Summary……Page 390
Suggested reading……Page 391
Problems……Page 392
15 0 Introduction……Page 394
15 1 Durability……Page 395
15 2 Display and controls……Page 397
15 3 Human interface……Page 401
15 4 Optical port……Page 402
15 5 Accessories, options, and features……Page 409
15 6 Safety……Page 411
15 7 Performing a fi ber-acceptance test……Page 414
15 7 1 Sequential steps of an acceptance test……Page 415
15 8 Measuring the splice attenuation……Page 417
15 8 1 Corrective actions……Page 418
15 9 When should OTDR traces be taken?……Page 419
15 10 1 What measurements are required?……Page 420
15 11 Field technician’s top-ten list……Page 421
Problems……Page 422
Glossary of Terms……Page 424
Mathematical Glossary……Page 440
Answers to Problems……Page 446
Index……Page 448