Fiber sensing technologies have enabled both fundamental studies and a wide spectrum of applications in every aspect of life. This book highlights the recent advancement in fiber sensing technologies based on newly developed sensing mechanisms, advanced fiber structures, and functional materials. In particular, the integration of functional materials with different electrical, optical, thermal, or mechanical properties into a single fiber offers a wealth of new opportunities in sensing. The book covers the major developments in novel fiber materials, such as semiconductors, metals, polymers, soft glasses, and carbon materials, as well as the sensing applications based on both single fiber and multi-dimensional fiber arrays for temperature, light, strain, vibration, electric and magnetic fields, hazardous chemicals, gases, and physiological signals.