The book contains: Evolution of fiber optic system - Element of an Optical Fiber Transmission link- Ray Optics-Optical Fiber Modes and Configurations - Mode theory of Circular Wave guides - Overview of Modes-Key Modal concepts - Linearly Polarized Modes - Single Mode Fibers-Graded Index fiber structure. Signal Degradation Optical Fibers: Attenuation - Absorption losses, Scattering losses, Bending Losses, Core and Cladding losses, Signal Distortion in Optical Wave guides - Information Capacity determination - Group Delay - Material Dispersion, Wave guide Dispersion, Signal distortion in SM fiber`s-Polarization Mode dispersion, Intermodal dispersion, Pulse Broadening in GI fibers-Mode Coupling - Design Optimization of SM fibers-RI profile and cutoff wavelength.