Far-field diffraction pattern
In telecommunication, far-field diffraction pattern (Fraunhofer diffraction pattern) is the diffraction pattern of a source (such as an LED, ILD, or the output end of an optical fiber) observed at an infinite distance from the source.A far-field pattern exists at distances that are large compared with s 2/λ, where s is a characteristic dimension of the source and λ is the wavelength. For example, if the source is a uniformly illuminated circle, then s is the radius of the circle.
The far-field diffraction pattern of a source may be observed at infinity or (except for scale) in the focal plane of a well-corrected lens. The far-field pattern of a diffracting screen illuminated by a point source may be observed in the image plane of the source.
Contrast with near-field diffraction pattern.
Source: from Federal Standard 1037C
