An Optical Frequency-Domain Reflectometer (OFDR), based upon the Optical Backscatter Reflectometry technology, allowing measurements in reflection (return loss, phase derivative) and transmission (insertion loss, group delay) of fiber optic or waveguide components in spatial/time. An Optical Frequency-Domain Reflectometer (OFDR), based upon the Optical Backscatter Reflectometry technology, allowing measurements in reflection (return loss, phase derivative) and transmission (insertion loss, group delay) of fiber optic or waveguide components in spatial/time. Fiber Optical Test deliver OFDR solutions that leverage fine-tuned signal processing and rapid data acquisition to reveal the smallest anomalies in fiber infrastructure. Luna's Optical Backscatter Reflectometers (OBRs) operate on a principle known as optical. Introduction to the principle of OFDR optical frequency domain reflectometry 1. Scattering in the fiber When light travels through an inhomogeneous medium, it travels in all directions. This is the scattering of light. For example, a clear sky appears blue, and sea water is blue.