Digital Communications Test and Measurement

A Comprehensive Guide to Physical Layer Test and Measurement of Digital Communication Links

Today's new data communication and computer interconnection systems run at unprecedented speeds, presenting new challenges not only in the design, but also in troubleshooting, test, and measurement. This book assembles contributions from practitioners at top test and measurement companies, component manufacturers,and universities. It brings together information that has never been broadly accessible before—information that was previously buried in application notes, seminar and conference presentations, short courses, and unpublished works.

Readers will gain a thorough understanding of the inner workings of digital high-speed systems, and learn how the different aspects of such systems can be tested. The editors and contributors cover key areas in test and measurement of transmitters (digital waveform and jitter analysis and bit error ratio), receivers (sensitivity, jitter tolerance, and PLL/CDR characterization), and high-speed channel characterization (in time and frequency domain). Extensive illustrations are provided throughout.

Coverage includes

• Signal integrity from a measurement point of view

• Digital waveform analysis using high bandwidth real-time and sampling (equivalent time) oscilloscopes

• Bit error ratio measurements for both electrical and optical links

• Extensive coverage on the topic of jitter in high-speed networks

• State-of-the-art optical sampling techniques for analysis of 100 Gbit/s + signals

• Receiver characterization: clock recovery, phase locked loops, jitter tolerance and transfer functions, sensitivity testing, and stressed-waveform receiver testing

• Channel and system characterization: TDR/T and frequency domain-based alternatives

• Testing and measuring PC architecture communication links: PCIexpress, SATA, and FB DIMM

Preface xxi About the Authors xxvii Acknowledgments xxxiii Chapter 1 Fundamentals of Digital Communications Systems 1

1.1 Introduction 2

1.2 System Architectures 2

1.3 Line Coding of Digital Signals 12

1.4 Electrical Signaling 23

1.5 Summary 26

1.6 References 26

2.1 Definition of Jitter 29

2.2 Jitter as a Statistical Phenomenon34

2.3 Total Jitter and Its Subcomponents 38

2.4 Analytical Solutions for Jitter Mixtures 42

2.5 The Dual Dirac Model 52

2.6 Summary 58

2.7 References 59

3.1 Introduction 62

3.2 Encoders and Modulation Code Examples 68

3.3 Telephone System History and Evolution 89

3.4 SONET Design Requirements 107

3.5 Measuring the Band-Pass Response 112

3.6 Jitter 114

3.7 Measuring Power Supply Noise Immunity 120

3.8 Power Supply Distribution, Grounding, and Shielding 123

3.9 Measuring SONET Jitter 124

3.10 Modulation Codes for the Last Mile 140

3.11 Gigabit Ethernet 149

3.12 Summary 163

3.13 References 164

4.1 Basics of Bit Error Ratio Testing 170

4.2 Bit Error Ratio Statistics 178

4.3 Advanced BER Measurement Topics 192

4.4 Summary 193

4.5 References 193

5.1 Basics of BERT Scan Measurements 195

5.2 Sample Delay Scan 200

5.3 Sample Threshold Scan 226

5.4 Full Eye Scan 228

5.5 Spectral Jitter Decomposition 238

5.6 Summary 241

5.7 References 242

6.1 Principles of Operation of Real-Time Digital Oscilloscopes 245

6.2 Eye Diagram Analysis on Real-Time Instruments 258

6.3 Methods of Analyzing Individual Jitter Components 279

6.4 Analysis of Composite Jitter 299

6.5 Measurement Procedures 302

6.6 Interpreting Jitter Measurement Results 315

6.7 Summary 325

6.8 References 327

7.1 Sampling Oscilloscope Basics 330

7.2 Triggering the Oscilloscope 330

7.3 Oscilloscope Bandwidth and Sample Rate 331

7.4 Waveform Acquisition Process for the Sampling Oscilloscope 335

7.5 Sources of Instrumentation Noise 346

7.6 Parametric Analysis of Waveforms 350

7.7 The Effect of Oscilloscope Bandwidth on Waveform Results 353

7.8 Measurements of the Eye Diagram 358

7.9 Return-to-Zero Signals 382

7.10 Advanced Jitter Analysis 387

7.11 Summary 417

7.12 References 418

8.1 Introduction 422

8.2 Principles of Optical Sampling 427

8.3 Performance Measures of All-Optical Sampling Systems 441

8.4 Timebase Designs 464

8.5 Experimental Implementation and Key Building Blocks 475

8.6 Related Applications and Possible Future Directions 492

8.7 Summary 498

8.8 References 499

9.1 Oscillators and Phase Noise 506

9.2 Phase Locked Loops and Clock Synthesis 510

9.3 Clock Data Recovery Circuits 512

9.4 PLL and Clock Recovery Dynamic Behavior 517

9.5 Measuring PLL Dynamics 523

9.6 Measuring Phase Noise and Jitter Spectrum 525

9.7 Summary 531

9.8 References 532

10.1 Introduction 533

10.2 Jitter Tolerance: Basic Measurement Method and Test Setup 536

10.3 Generation of Jitter Tolerance Test Signals 539

10.4 Jitter Tolerance Measurement Method and Test Setup 555

10.5 Summary 560

10.6 References 560

11.1 Introduction: Optical Digital Receivers 564

11.2 The Basics of Optical Sensitivity Measurements 565

11.3 BER Calculations in Real Communications Systems 588

11.4 Summary 602

11.5 References 603

12.1 The Need for High-Speed Serial Communication 606

12.2 Early High-Speed Optical Stressed-Eye Tests 607

12.3 BER versus OSNR 609

12.4 10 Gigabit Ethernet: IEEE 802.3ae 618

12.5 The Advent of Electronic Dispersion Compensation 629

12.6 LRM Stress Testing (IEEE 802.3aq) 634

12.7 Future Standards 641

12.8 Summary 654

12.9 References 655

13.1 Measurements and Characterization of Interconnects 658

13.2 Modeling of System Performance from Measurements 689

13.3 Summary 709

13.4 References 710

14.1 Introduction 714

14.2 Understanding Network Analyzer Hardware 716

14.3 Understanding S-Parameters 729

14.4 Error Correction and Calibration Methods 740

14.5 Graphical Representations 749

14.6 Example Devices 758

14.7 Summary 783

14.8 References 783

15.1 Introduction 785

15.2 Multiple Gigabit per Second Computer Chip-to-Chip I/O Link Architectures 788

15.3 Chip-to-Chip Link System BER and Signaling Tests 800

15.4 Testing Examples 811

15.5 Future Technology Trends for High-Speed Links 815

15.6 Summary 817

15.7 References 817

Dennis Derickson is an assistant professor at California Polytechnic State University. He spent eighteen years as member of technical staff and project manager at Hewlett-Packard and Agilent Technologies before serving as applications engineering manager for Cierra Photonics. He has authored or coauthored fifty publications in high-speed communications and is the editor of Fiber Optic Test and Measurement (Prentice Hall, 1998). Dennis has a Ph.D. from the University of California, Santa Barbara.

Marcus Müller is an R&D lead engineer with Agilent Technologies' High-Speed Digital Test segment in Boeblingen, Germany. He specializes in bit error ratio and jitter analysis of high-speed links, and has contributed to new methods for total jitter measurement at low bit error ratios, and jitter tolerance test. Marcus received his M.Sc. degree from Stuttgart University, Germany, in 1999.