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In physics, coherence length is the propagation distance from a coherent source to a point where an electromagnetic wave maintains a specified degree of coherence. The significance is that interference will be strong within a coherence length of the source, but not beyond it. This concept is also commonly used in telecommunication engineering.
Additional recommended knowledge
In radio-band systems, the coherence length is approximated by
In optical communications, the coherence length L is given approximately by
Coherence length is usually applied to the optical regime.
The expression above is a frequently used approximation. Due to ambiguities in the definition of spectral width of a source, however, the following definition of coherence length has been suggested:
The coherence length is the optical path length difference of a self-interfering laserbeam which corresponds to a 50% fringe visibility, where the fringe visibility is defined as
where I is the fringe intensity.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Coherence_length". A list of authors is available in Wikipedia.|