In fiber optics, a loss of optical power at a splice or connector, caused by a lateral, i.e., transverse, offset of the mating fiber cores, which offset causes an imperfect transfer of the optical signal from the "transmitting" fiber to the "receiving" fiber. Note: The effect of a given amount of lateral offset will depend on other parameters such as the relative diameters of the respective cores. For example: if, because of manufacturing tolerances, the "transmitting" core is smaller than the "receiving" core, the effect will be less than if both cores were the same size. 2. An analogous loss of optical power caused by lateral misalignment of the fiber and optical source. Synonym transverse offset loss.