Introduction. Optical Fibers. Optical Transmitters. Optical Receivers and Transmission Performance: Fundamentals. Optical Coherent Detection and Processing Systems. Differential Phase Shift Keying Photonic Systems. Multilevel Amplitude and Phase Shift Keying Optical Transmission. Continuous Phase Modulation Format Optical Systems. Frequency Discrimination Reception for Optical Minimum Shift Keying. Partial Responses and Single-Sideband Optical Modulation. OFDM Optical Transmission Systems. Digital Signal Processing in Optical Transmission Systems under Self-Homodyne Coherent Reception. DSP-Based Coherent Optical Transmission Systems. DSP Algorithms and Coherent Transmission Systems. Optical Soliton Transmission System. Higher-Order Spectrum Coherent Receivers. Temporal Lens and Adaptive Electronic/Photonic Equalization. Comparison of Modulation Formats for Digital Optical Communications.