Optical fibers are transparent fibers which are produced by drawing glass or plastic to a diameter slightly bigger than that of human hair. They are flexible in nature and are used to transmit light. They work on the principle of total internal reflection of light and are immune to electromagnetic interferences. Depending upon the refractive index, optical fibers are classified into step index and graded index fibers. They find extensive applications in the fields of telecommunication, computer networking, power transmission and sensors. Some of the advantages of optical fibers are cost effectiveness, non-flammability, lightweight and low signal degradation. This book includes some of the vital pieces of work being conducted across the world, on various topics related to optical fibers. It aims to shed light on some of the unexplored aspects of optical fibers and the recent researches in this field. As this field is emerging at a rapid pace, the contents of this book will help the readers understand the modern concepts and applications of the subject.