Few technologies have had as much impact on society as fiber optics. These tiny hair-sized glass wires have deeply transformed the way we access information, our modes of communication and even the behavior of consumers. Today, optical fibers are omnipresent in modern optical systems, so that a solid background in fiber optics is a prerequisite for any engineer or scientist who has the ambition to become a specialist in the conception and application of systems based on light signals. The aim of this book is to provide advanced students and young researchers with extensive knowledge about optical functions and their novel uses in the toolkit of advanced fiber optics. After an initial chapter summarizing the basic properties and fabrication of optical fibers, each chapter addresses an advanced feature of fiber optics, such as light polarization, amplification and the emission of light by fibers, nonlinear optical interactions, photonic crystal fibers, and generation of a light supercontinuum. Numerous concepts behind novel applications are presented, including the rapidly growing field of distributed sensing, for which natural scattering processes in the fiber material are exploited. The book also addresses the constant search for alternative materials, such the use of polymer optical fibers and the application of chalcogenide and soft glasses, that promise to turn optical fibers into an even more efficient and omnipresent tool for advanced photonics.