6.1 Introduction6.2 Intensity Modulation and Direct Detection Transmission6.2.1 Fiber-Optic Transmission Systems6.2.1.1 Wavelength Division Multiplexing6.2.1.2 Transmission System Performance Indicators6.2.2 Ideal IM–DD Transmission6.2.3 Analysis of a Realistic Single-Channel IM–DD System6.2.3.1 Evaluation of the BER in the Presence of Channel Memory6.2.3.2 NRZ Signal after Propagation6.2.3.3 RZ Signal after Propagation6.2.3.4 Realistic Receiver Noise Model6.2.3.5 Performance Evaluation of an Unrepeated IM-DD System6.2.4 Performance of Non-Regenerated NRZ Systems6.2.4.1 Dispersion-Compensated NRZ IM-DD Systems6.2.5 Performance of Non-Regenerated Return to Zero Systems6.2.6 Unrepeated Wavelength Division Multiplexing Systems6.2.6.1 Linear Interference in Wavelength Division Multiplexing Systems6.2.6.2 Nonlinear Interference in Wavelength Division Multiplexing Systems6.2.6.3 Jitter, Unperfected Modulation, Laser Linewidth, and Other Impairments6.3 Intensity Modulation and Direct Detection Systems Using Optical Amplifiers6.3.1 Long-Haul and Ultra-Long-Haul Transmission: Performance Evaluation6.3.2 Design of Long-Haul Transmission Systems6.3.2.1 Erbium-Doped Optical Fiber Amplifier Amplified Systems Design6.3.2.2 Long-Haul Transmission at 40 Gbit/s6.3.2.3 Long-Haul Transmission: Realistic Systems Characteristics6.3.3 Design of Ultra-Long-Haul Transmission Systems6.3.3.1 Ultra-Long-Haul Transmission at 10 Gbit/s: Draft Design6.3.3.2 Ultra-Long-Haul Transmission Systems: Penalties, Evaluation, and Simulation Results6.3.3.3 Ultra-Long-Haul Transmission at 40 Gbit/s6.3.3.4 Ultra-Long-Haul Systems with Electronic Pre-Compensation6.3.4 Single-Span Systems6.3.4.1 Single-Span Systems with Intensity Modulation and All Raman Amplification6.3.4.2 Single-Span Systems with Differential Phase Shift Keying Transmission and Raman Amplification6.3.4.3 Single-Span Systems with Electronic Pre-Distortion at 10 Gbit/s6.3.5 Metropolitan Optical Rings6.3.5.1 Transmission in Dense Wavelength Division Multiplexing Metropolitan Ring6.3.5.2 Transmission in Coarse Wavelength Division Multiplexing Metropolitan Ring6.4 Alternative Modulation Formats6.4.1 Single Side Band Modulation6.4.2 Duobinary Modulation6.5 Hardware Architecture of Optical Transmission Systems6.5.1 Mechanical Structure of a Dense Wavelength Division Multiplexing System6.5.1.1 Signal Cards6.5.1.2 Support Cards6.5.1.3 Control Cards6.5.1.4 Redundancies6.5.2 Backplane Architecture6.5.3 Backplane Bus Protocols6.5.4 System Thermal DesignReferences