OVERFILL

1. The condition that prevails when the numerical aperture of an optical source , such as a laser , light-emitting diode , or optical fiber , exceeds that of the driven element, e.g., optical fiber core . 2. The condition that prevails when the beam diameter of an optical source, such as a laser, light-emitting diode, or optical fiber, exceeds that of the driven element, e.g., optical fiber core. Note: In optical communications testing, overfill in both numerical aperture and mean diameter ( core diameter or spot size ) is usually required.