Graded-index fiber
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2007-10-28T20:25:05Z
Arghlookamonkey
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In [[fiber optics]], a '''graded-index''' or '''gradient-index fiber''' is an [[optical fiber]] whose [[Fiber_optics#Principle_of_operation|core]] has a [[refractive index]] that decreases with increasing radial distance from the [[fiber axis]] (the imaginary central axis running down the length of the fiber).
Because parts of the core closer to the fiber axis have a higher refractive index than the parts near the cladding, light rays follow [[sinusoidal]] paths down the fiber.
The advantage of the graded-index fiber compared to [[Multi-mode optical fiber|multimode step-index fiber]] is the considerable decrease in [[modal dispersion]].
The most common refractive index profile for a graded-index fiber is very nearly parabolic. The [[parabolic profile]] results in continual refocusing of the rays in the core, and minimizes modal dispersion.
This type of fiber is normalized by the International Telecommunications Union ITU-T at recommendation G.651:
“Characteristics of a 50/125 μm multimode graded index optical fiber cable”
==See also==
*[[Step-index profile]]
*[[Power-law index profile]]
*[[Gradient index optics]]
==References==
*[[Federal Standard 1037C]]
*[[MIL-STD-188]]
{{optics-stub}}
[[Category:Optical fiber]]