Contents xv
9. Integrated Guided-Wave Photonic Transmitters .........................................................457
9.1 Introduction ...............................................................................................................457
9.2 Optical Modulators ...................................................................................................458
9.2.1 Phase Modulators ........................................................................................458
9.2.2 Intensity Modulators ...................................................................................460
9.2.2.1 Phasor Representation and Transfer Characteristics ..............460
9.2.2.2 Bias Control ...................................................................................462
9.2.2.3 Chirp Free Optical Modulators .................................................. 462
9.2.2.4 Structures of Photonic Modulators ............................................464
9.2.2.5 Typical Operational Parameters .................................................464
9.3 Traveling Wave Electrodes for Integrated Modulators........................................465
9.3.1 Introduction ..................................................................................................466
9.3.2 Numerical Formulation ..............................................................................467
9.3.2.1 Discrete Fields and Potentials ....................................................467
9.3.2.2 Electrode Line Capacitance, Characteristic Impedance
and Microwave Effective Index ..................................................469
9.3.2.3 Electric Fields E
x
and E
y
and the Overlap Integral ..................471
9.3.3 Electrode Simulation and Discussions .....................................................471
9.3.3.1 Grid Allocation and Modeling Performance ...........................471
9.3.3.2 Model Accuracy ............................................................................ 474
9.3.4 Electro-Optic Overlap Integral, Γ .............................................................. 476
9.3.5 Tilted Wall Electrode ...................................................................................478
9.3.6 Frequency Responses of Phase Modulation by Single Electrode ......... 481
9.3.7 Remarks .........................................................................................................484
9.4 Lithium Niobate Optical Modulators: Devices and Applications .....................485
9.4.1 Mach-Zehnder Interferometric Modulator and Ultra-High Speed
Advanced Modulation Formats .................................................................485
9.4.1.1 Amplitude Modulation................................................................486
9.4.1.2 Phase Modulation ........................................................................486
9.4.1.3 Frequency Modulation ................................................................486
9.4.2 LiNbO
3
MZIM Fabrication .........................................................................487
9.4.3 Effects of Angled-Wall Structure on RF Electrodes ................................488
9.4.4 Integrated Modulators and Modulation Formats ...................................490
9.4.5 Remarks .........................................................................................................492
9.5 Generation and Modulation of Optical Pulse Sequences ...................................492
9.5.1 Return-to-Zero Optical Pulses ...................................................................492
9.5.1.1 Generation .....................................................................................492
9.5.1.2 Phasor Representation .................................................................493
9.5.2 Differential Phase Shift Keying .................................................................498
9.5.2.1 Background ...................................................................................498
9.5.2.2 Optical Differential Phase Shift Keying Transmitter .............499
9.6 Generation of Modulation Formats ........................................................................500
9.6.1 Amplitude Shift Keying .............................................................................500
9.6.1.1 Amplitude–Modulation Amplitude Shift Keying-Non-
Return-to-Zero and Amplitude Shift Keying-Return-to-Zero .... 500
9.6.1.2 Amplitude–Modulation on-off Keying Return-to-Zero
Formats ..........................................................................................501
9.6.1.3 Amplitude–Modulation Carrier-Suppressed Return-to-
Zero Formats .................................................................................501