In waveguide design and construction, angular misalignment loss is Power loss caused by the deviation from optimum angular alignment of the axes of source-to-waveguide, waveguide-to-waveguide, or waveguide-to-detector. Note 1: The waveguide may be dielectric (an optical fiber) or metallic.

Note 2: Angular misalignment loss does not include lateral offset loss and longitudinal offset loss.

Source: from Federal Standard 1037C