The CPR losses are the ratio of the total radiated power of a multimode fiber to the power portion that is coupled into a single mode fiber. The Coupled Power Ratio parameter is generally used to evaluate the matching conditions of the light source into a multimode fiber. In some standards, the CPR value is used for attenuation measurements in installed optical transmission equipment. For example, in TIA/ EIA 526-11A.
A higher CPR value means that there is a high loss in the coupling between a multimode fiber and a single mode fiber, corresponding to an Overfilled Launch( OFL); a lower CPR value represents an Underfilled Launch (UFL).