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Spie Press Book

Digital and Analog Fiber Optic Communications for CATV and FTTx Applications
Author(s): Avigdor Brillant
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Book Description

This book is intended to provide a step-by-step guide to all design aspects and tradeoffs from theory to application for fiber-optics transceiver electronics. Presenting a compendium of information in a structured way, this book enables the engineer to develop a methodical design approach, a deep understanding of specifications parameters and the reasons behind them, as well as their effects and consequences on system performance, which are essential for proper component design. Further, a fundamental understanding of RF, digital circuit design, and linear and nonlinear phenomena is important in order to achieve the desired performance levels. Becoming familiar with solid-state devices and passives used to build optical receivers and transmitters is also important so one can effectively overcome design limitations.

The book is organized into six main sections covering the following subjects: a top level overview; optics, semiconductors, and passives; RF concepts; an introduction to CATV modems and transmitters; digital transceivers' performance, evaluation, and concepts; and integration and testing.

Copublished with Wiley Interscience.


Book Details

Date Published: 10 June 2008
Pages: 1090
ISBN: 9780819467577
Volume: PM174

Table of Contents
SHOW Table of Contents | HIDE Table of Contents
Preface / 10
Acknowledgement / 13
Glossary / 17
Abbreviations / 17
Constants and Symbols / 30
Part 1
Top Level General Overview
Chapter 1
WDM , Fiber to The X and Hybrid Fiber Coax Systems Technical Review / 32
1.1 Introduction / 32
1.2 Cable TV and Networks System Overview / 37
1.3 The Passive Optical Network and its Diversities / 44
1.4 Main Points of This Chapter / 53
1.5 References / 55
Chapter 2
Basic Structure of Optical Transceivers / 58
2.1 Analog CATV Receiver and Coax Cables / 58
2.3 Analog CATV Return-Path Receiver and Transmitter / 62
2.4 Digital Transceiver / 65
2.5 ITR Digital Transceiver and Analog Receiver / 68
2.6 Tunable Wavelength Transmitter Architecture / 70
2.7 Main Points of This Chapter / 71
2.8 References / 72
Chapter 3
Introduction to CATV Standards and Concepts of Operation / 73
3.1 Television System Fundamentals / 73
3.2 Video Bandwidth and Spectrum Considerations of Color TV / 79
3.3 Digital TV and MPEG Standards / 92
3.4 NTSC Frequency Plan and System Minimum Requirements / 107
3.5 Basic NTSC TV Signal Testing / 114
3.6 Main Points of This Chapter / 117
3.6 References / 119
Part 2
Optics Semiconductors and Passives
Chapter 4
Introduction to Optical Fibers and Passive Optical Fiber Components / 122
4.1 Single Mode Fiber / 123
4.2 Optical Fiber Connectors / 127
4.3 Optical Couplers / 130
4.4 WDM Multiplexers / 132
4.5 Optical Isolators and Circulators / 161
4.6 Main Points of This Chapter / 166
4.7 References / 169
Chapter 5
Optics Modules and Lenses / 174
5.1 Planar Lightwave Circuits / 174
5.2 Free-Space Bulk Optical WDM Modules / 180
5.3 Main Points of This Chapter / 193
5.4 References / 195
Chapter 6
Semiconductor Laser Diode Fundamentals / 198
6.1 Basic Laser Physics Concepts of Operation / 198
6.2 Semiconductor Laser Structure Gain Guided vs. Index Guided / 202
6.3 Longitudinal Modes and FP Lasers / 203
6.4 DFB and DBR Lasers / 205
6.5 Multiple Quantum Well Lasers / 209
6.6 Vertical Cavity Surface Emitting Lasers VCSEL / 213
6.8 Tunable Lasers / 215
6.9 Laser Characteristics in RF / 227
6.10 Quantum Efficiency / 233
6.11 Main Points of This Chapter / 235
6.11 References / 238
Chapter 7
Laser Dynamics: External Modulation for CATV and Fast Data Rates / 242
7.1 The Dynamic Response of a Semiconductor Laser / 242
7.2 Large Signal Deviation from the Basic Model / 250
7.3 Amplitude Phase Coupling (Chirp) / 252
7.4 Laser Distortions / 254
7.5 External Modulation / 269
7.6 Main Points of This Chapter / 277
7.7 References / 279
Chapter 8
Photodetectors / 283
8.1 Background of Detection and Photodetectors / 283
8.2 Junction Photodetector / 289
8.3 Avalanche Photodetector / 312
8.4 Bias Considerations / 318
8.5 Photodetection and Coherent Detection / 318
8.6 Main Points of This Chapter / 320
8.7 References / 323
Part 3
RF Concepts and the Basic Approach to Analog Receiver Design
Chapter 9
Basic RF Definitions and IMD Effects on TV Picture / 327
9.1 Distortions and Dynamic Range / 327
9.2 1-dB Compression Point and Third-Order Intercept Point Relations / 331
9.3 Amplifier Gain Reduction due to Third-Order Nonlinearity / 332
9.4 Cross-Modulation Effects / 335
9.5 AM to PM Effects / 336
9.6 Multitone Composite Triple Beat Relations / 336
9.7 RF Lineups NF Calculations and Considerations / 340
9.8 RF Lineups P1dB and IP3 Calculations and Considerations / 343
9.9 Mismatch Effects / 345
9.10 Main Points of This Chapter / 352
9.11 References / 354
Chapter 10
Introduction to Receiver Front-End Noise Modeling / 356
10.1 Noise Analysis Basics / 357
10.2 Noise Sources in an Optical Receiver / 361
10.3 Thermal Noise and Johnson Noise / 361
10.4 Shot Noise / 364
10.5 1/f Noise / 365
10.6 Carrier-to-Noise Ratio / 366
10.7 PIN Photodetector Noise Modeling / 378
10.8 APD Photodetector Noise Modeling / 379
10.9 Receiver Front-End Design Considerations / 383
10.10 Main Points of This Chapter / 394
10.11 References / 396
Chapter 11
Amplifiers Analysis and Design Concepts / 397
11.1 Noise Parameters of a Two-Port Device / 397
11.2 Two-Port Network Matching to Minimum Noise / 402
11.3 Noise Modeling of MESFET / 404
11.4 Noise Modeling of BJT / 408
11.5 MESFET Feedback Amplifier / 411
11.6 Distributed Amplifier / 417
11.7 Operational Transimpedance Amplifiers PIN TIA / 423
11.8 Biasing Methods / 434
11.9 Equalizers and Optimum placement of Equalizers / 438
11.10 Matched PIN VVA / 444
11.11 Examples For Noise Analysis CMOS and BJT RF IC Designs / 446
11.12 Main Points of This Chapter / 447
11.13 References / 450
Chapter 12
AGC Topologies and Concepts / 454
12.1 Feed-Forward AGC / 455
12.2 Feedback AGC / 457
12.3 Main Points of this Chapter / 497
12.4 References / 499
Chapter 13
Laser Power and Temperature Control Loops / 500
13.1 Automatic Power Control Loop (APC) / 500
13.2 Thermoelectric Cooler (TEC) Control / 503
13.3 Main Points of This Chapter / 514
13.4 References / 516
Part 4
Introduction to CATV MODEM and Transmitters
Chapter 14
QAM Modulation in CATV Optical Transmitters / 518
14.1 Quadrature Modulators / 518
14.2 Generating FM using QPSK Modulators / 519
14.3 Digital QAM Modulation / 520
14.4 Signal Impairments and Effects / 522
14.5 Jitter Phase Noise / 531
14.6 Residual AM Modulation Effects / 535
14.7 Non Linear Effects / 535
14.8 Error Vector Magnitude (EVM) and Modulation Error Ratio (MER) / 536
14.9 BER of M-ARY QAM / 537
14.10 Relationship Between Eb/No to C/N / 540
14.11 BER vs. Eb/No to C/N Performance Limits / 542
14.12 Main Points of This Chapter / 543
14.13 References / 545
Chapter 15
Introduction to CATV MODEM / 546
15.1 QAM MODEM Block Diagram / 546
15.2 MPEG Scrambler Descrambler / 547
15.3 Codes Concept / 550
15.4 Reed Solomon Codes / 551
15.5 Interleaver Deinterleaver / 553
15.6 Trellis Coded Modulation / 555
15.7 M-Ary QAM Transmitter Design / 557
15.8 M-Ary QAM Receiver Design / 564
15.9 Main Points of This Chapter / 588
15.10 References / 591
Chapter 16
Linearization Techniques / 595
16.1 Electronic Linearization Methods in CATV and Cellular Transmitters / 595
16.2 Push-Pull / 610
16.3 Optical Linearization Methods in CATV Transmitters / 618
16.4 CATV Transmitter Structure / 625
16.5 Main Points of this Chapter / 627
16.6 References / 629
Chapter 17
System Link Budget Calculation and Impairments Aspects / 631
17.1 Link Budget / 631
17.2 Clipping Induced Nonlinear Distortions / 631
17.3 Multiple Optical Reflections / 631
17.4 Disperssion Induced Nonlinear Distortions / 631
17.5 Optical Fiber Nonlinear Effects / 632
17.6 Integrated Triplexer Coexistence / 632
17.9 Main Points of this Chapter / 632
17.10 References / 633
Part 5
Digital Transceivers Performance, Evaluation, and Concepts
Chapter18
Introduction to Digital Data Signals and Design Constrains / 635
18.1 Eye Analysis and BER / 635
18.2 Extinction Ratio / 637
18.4 Mode Partition / 640
18.5 Timing Jitter / 644
18.6 Relative Intensity Noise / 647
18.7 Minimum Detectable Signal MDS and Optical Power / 649
18.8 Digital Through Analogue / 651
18.10 Clock and Data Recovery (CDR) / 657
18.11 Main Points of This Chapter / 664
18.12 References / 667
Chapter19
Transceivers and Tunable Wavelength Transceiver Modules / 669
19.1 Burst Mode / 669
19.2 Wavelength Lockers and Wavelength Control Loop / 695
19.3 Transceiver Housing TOSA ROSA Structure and Integration / 699
19.5 Main Points of This Chapter / 709
19.6 References / 711
Part 6
Integration and Testing / 716
Chapter 20
Cross Talk Isolation / 717
20.1 Introduction / 717
20.2 Desensitization in Wideband Systems with Overlapping Rx/Tx BW / 717
20.3 Wide Band PRBS NRZ Interference Analysis / 720
20.4 EMI RFI Sources Theory For Shielding / 723
20.5 Ground Discipline Theory for Shielding and Minimum Emission / 724
20.6 Emission and Reception Mechanisms in Integrated Modules / 725
20.7 Differential Signal / 728
20.8 Important Definitions and Guidelines / 729
20.9 Brief about Transmission Lines / 729
20.10 Main Points of This Chapter / 731
References / 733
Chapter 21
Test Setups / 735
21.1 CATV Power Measurement Units / 735
21.2 OMI Calibration using PhotoDetector / 735
21.2 CATV Power Measurement Units / 737
21.3 Two Tone Test / 738
21.4 Multitone Test / 740
21.5 AGC Calibration Using Pilot Tone / 743
21.6 Feedback AGC Performance under Video Modulated Signal / 744
21.7 Cross Talk Test Methods / 748
21.8 Understanding Analog Receiver Specification / 750
21.9 Main Points of This Chapter / 753
21.10 References / 755

Preface

As data rates increase, there is a greater need to involve microwave engineering experience with digital design. The internet has created the need for a wider understanding of different aspects of system performance. For instance, the traditional digital designer must be more familiar with the root cause for his high-speed link performance tradeoffs such as sensitivity, bit error rate (BER), eye diagrams, jitter, etc. Some of those parameters require the knowledge and background of a radio frequency (RF) engineer, and having fundamental understanding of passive and active network design. Such a design may include jitter, and all RF engineers are familiar with its spectral definition of phase noise. Phase noise as we all know is a stochastic process; however, jitter of an eye diagram is composed from both the stochastic process and the deterministic process. An experienced RF engineer or communications engineer would try to optimize the phase response of the data transmission line so it would have a linear phase response. This way the group delay is constant and all the harmonics of the digital signal propagates at the same velocity and the deterministic jitter is minimized. There are many other factors affecting the image performance such as matching, which creates reflections and double images. That example shows the essential wide background required from fast-logic designers.

Any switch or router contains fast-logic and optics interfaces that operate at high speed. Moreover, as CATV (community aperture TV, cable TV) technology advanced, its video transport and return path are wired by fiber. Therefore, it is much more important to have a full understanding of all design aspects of fiber optics transceivers in order to meet the system requirements. Modern CATV transmissions are shifting from traditional analog to higher modulation qualities such as high-order quadrature amplitude modulation (QAM); the traditional RF engineer needs to better understand the effects of his designs on the signal quality and distortions. There is also a need to understand the effects of amplitude modulation to amplitude modulation (AM to AM) on the second-order and third order distortions. For CATV, multitone transport is an issue; hence, the designer has to understand the RF-chain lineup tradeoffs such as carrier-to-noise ratio (CNR) versus compression and the affects on composite second order (CSO) and composite triple beat (CTB) in the receiver channel. The RF engineer has to understand the effects of AM to AM and AM to PM (phase modulation) on the QAM signal constellation. Hence, the RF engineer should have a wider background in digital communications and modulation techniques. Additionally, the RF engineer, as well as the digital design engineer, should have a fundamental background on optical devices, at least on their equivalent circuit and impedance matching in order to reach high-spec system performance.

In some advanced designs, both analog and digital disciplines have to coexist and operate in the same space and packaging enclosure. As the technology of semiconductors improves, the size of the components is getting smaller, and the printed-circuit-board (PCB) population density is increasing, becoming more crowded. Subassembly such as the optical transceiver has to be smaller in one hand, and faster with higher data rates on the other. For a fast digital transceiver packaged together with an analog CATV receiver, creating an integrated optical triplexer module (ITR) is more challenging. ITR is used to convert digital traffic from light into electronic signal and visa versa, and it also converts sensitive signals from light into analog signals, where X-talk becomes an issue. Both designers should have a full understanding of X-talk mechanisms, ground disciplines, and radiation from transmission lines, as well as the spectral content of the digital signal at different series patterns, shielding methods and some background in fields in order to solve the X-talk problem. The requirement from such a high level of integration is coexistence, meaning each system should operate without interfering with the other. Consequently the sensitive and susceptible channel is the analog channel. However, proper design of such an integrated system is possible, yielding the required high performances.

There are several excellent books covering many subjects related to fiber optics; however, the goal of this book is to guide inexperienced and experienced digital and RF engineers through fiber optics transceiver electronic designs step by step, while focusing on all design aspects and tradeoffs from theory to application as much and as possible. This book condenses the necessary information and design methods into several structured subjects. It provides the engineer with a proper methodical design approach, by observing the component requirements given from a system design level. This way, the engineer has a deep understanding of specifications parameters, the reasons behind it, as well as its effects and consequences on system performance, which are essential for proper component design. Further, a fundamental understanding of RF and digital-circuit design and linear and nonlinear phenomenon are important in order to achieve the desired performances. Becoming familiar with solid state devices and passives used to build optical receivers and transmitters is important for overcoming design limitations in an effective way.

The book is organized in 6 main sections covering the following subjects:

Part 1 Top Level Overview

This part contains 3 chapters providing the reader a top down structured approach to get familiar with hybrid fiber coax systems (HFC), This part provides information about several architectures of data transport carried over fiber and interfaces, which includes, MMDS, LMDS, CATV ReturnPath and internet with some glimpse to protocol stack and last mile last feet concepts. This section provides information about the ITU grid and optical bands and advantages of fiber as transmission lines and WDM concept. This whole review leads to the FTTx architectures concepts.

After the fundamental background about the system needs, there is an introductory to the structure of the last mile optical to coax interfacing. This review provides different topologies for digital and analog receivers, which lead to the FTTx integrated solution of access transponder, containing both CATV receiver and digital transceiver. Additionally, tunable laser transponder architecture is explained as diverse of ordinary digital transceivers solution for METRO WDM architectures.

The last part is an introduction to TV and CATV standards and concept of operation. The main idea behind that part even though it looks as not related, is to provide detailed information about this unique signal transport and the implication of system specifications reflecting the FTTx platform and CATV receivers.

Part 2 Optics Semiconductor and Passives

This section contains 5 chapters and provides detailed information about different optical building blocks of fiber to coax and coax to fiber converters, which were reviewed in the first part. In this section the building blocks are categorized to lasers photodetectors and passives such as couplers WDM filters Triplexers Duplexers etc. Each type of device physics is explored and analyzed. Analogies to microwaves are provided at some points to guide those introduced first time with fiber optics about the similarities.

Part 3 RF Concepts

In this section there are 6 chapters. This section deals in depth with RF topologies to design highly linear analog CATV receivers, and provides wide background about structure of devices for high speed digital design. At first basic RF definitions are provided and simple RF lineups are reviewed. CSO CTB beat counts are explained. IMD effects on CATV picture are analyzed. An introductory to noise and limits are explored and investigated. Different kinds of RF amplifiers and frontend matching are investigated. Pushpull distortions and analysis techniques are explored. On the digital side various TIAs are analyzed such as distributed amplifiers for wide band data rates of 10GBit and 40GBit (which can be a laser driver). Structure and limitations of operational amplifier TIA are investigated. Detailed AGC (automatic gain control) analysis is provided with analogies to APC (automatic power control) and TEC (thermoelectric cooler) loop designs.

Part 4 Introduction to CATV Modem and Transmitters.

This section contains 4 chapters guiding to the CATV MODEM concept of operation. At first background about QAM modulators and impairments is reviewed. After then, CATV MODEM structure is explored explaining the different building blocks such as coding, synchronization and limitations such as phase noise. From there the next part of linear transmission is investigated. Predistortion techniques such as optical and electrical are analyzed and reviewed. Link analysis and derived OMI specs are investigated and explained as a summary. Jitter and phase noise are reviewed. Fiber effects are introduced.

Part 5 Digital Transceivers Performance Evaluation and Concepts.

This section contains two chapters structured top down. It is guiding the reader from digital signal definitions to the concept of a digital transceiver and tunable laser transponder architecture. Performance analysis and synthesis are provided. At first, fundamental definitions of digital transport are such as eye diagram, jitter extinction ratio are reviewed using MathCAD. Data formats such as NRZ RZ and performances over fiber are investigated. CDR (clock data recovery) structure is analyzed. After having solid background, transceivers and tunable laser transponders are investigated. Burst mode concepts and burst mode AGC are explained in detail.

Part 6 Integration and Testing

This section contains two chapters and focuses on integration problems and methods to test performances. EMI RFI problems within FTTx ITR platform are analyzed. XTalk between digital to analog parts in the FTTx transponder is investigated and methodologies to overcome interferences are provided. Analytical methods are given.

The next chapter in this section provides original methods for testing and evaluating FTTx platform compliance to the NCTA specifications. At the end, a practical FTTx receiver specification is reviewed and analyzed.

At the end of each chapter, a summary of main points studied in that chapter is provided.
This way one could condense key points in order to have the main idea and concepts behind each chapter.

Avi Brillant
September 2007


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