This book discusses the theories and advanced technologies associated with fiber laser and amplifier devices. It includes three brand-new chapters on cutting-edge techniques and discusses Q-switch fiber lasers, principles of mode-locked fiber lasers and applications, high power Yb-doped fiber lasers, visible fluoride fiber lasers, Tm-Doped mode locked fiber lasers at 2um, Ho-doped mode-locked fiber lasers, and 1.3um fiber amplifiers.