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 fiber optics 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. Authors are from the Standards laboratories of Australia, Canada, England, Germany and the USA. This book includes latest techniques and practice of laboratory measurements to achieve the highest accuracy in the use of sources or detectors; unique illustrations of the apparatus and measurement techniques; practical measurement examples of calibration with full uncertainty analysis; comprehensive treatment of optical standards such as sources, detectors and radiometers. It also includes a complete chapter on laser power measurements and standards for fiber optic measurements, a complete chapter on correlations in radiometry and practical examples, and a chapter devoted to diffraction effects in radiometry.