This book deals with the practice of Optical Radiation Measurements with introductory material to introduce the topics discussed. It will be most useful for students, scientists and engineers working in any academic, industrial or governmental projects related to optical radiation. The book contains chapters that treat in detail the procedures and techniques for the characterization of both sources and detectors to the highest degree of accuracy and reliability. It has a chapter devoted specifically to optical measurements of laser sources and fiberoptics for communication and a chapter devoted to uncertainty in measurement and its treatment with real examples of optical measurements. The book contains introductory materials that will allow a newcomer to radiometry to develop the expertise to perform exacting and accurate measurement. The authors stress the various causes of uncertainty in each phase of a measurement and thus allow for users to arrive at a correct assessment of their uncertainty of measurement in their particular circumstance.