This book is written from the point of view of prospective users, with a practical rather than purely theoretical approach, and discusses how optical fiber sensors can be applied to the detection of biophysical and biological quantities inside the body. The aim of the authors is to close the gap between the technologies and their application in the biomedical and clinical world. The book merges three key aspects: on one side it explores the principles of photonics and optical sensing and includes details about high-density distributed sensors, fiber Bragg gratings and fabry-perot interferometer; on the other side it examines biomedical applications, diagnostics and clinical procedures in gastroscopy, urology and neurology; and to bridge the two sides, it outlines how the fiber-optic sensing devices, developed in research labs, undergo the process of packaging, standardization and certification to become a commercially viable products. The authors highlight the competitive advantages fiber-optic sensors bring both in present and in emerging applications, with visual aids and application reviews. Readers will gain a thorough understanding of which technology to use and adopt and how to connect technologies with their respective applications.