For an optical fiber, a step-index profile is a refractive index profile characterized by a uniform refractive index within the core and a sharp decrease in refractive index at the core-cladding interface so that the cladding is of a lower refractive index. The step-index profile corresponds to a power-law index profile with the profile parameter approaching infinity. The step-index profile is used in most single-mode fibers[1] and some multimode fibers.[2]
![](http://178.128.105.246/cars-http-upload.wikimedia.org/wikipedia/commons/thumb/b/b4/Step-index-profile.svg/220px-Step-index-profile.svg.png)
A step-index fiber is characterized by the core and cladding refractive indices n1 and n2 and the core and cladding radii a and b. Examples of standard core and cladding diameters 2a/2b are 8/125, 50/125, 62.5/125, 85/125, or 100/140 (units of μm). The fractional refractive-index change . The value of n1 is typically between 1.44 and 1.46, and is typically between 0.001 and 0.02.
Step-index optical fiber is generally made by doping high-purity fused silica glass (SiO2) with different concentrations of materials like titanium, germanium, or boron.
Modal dispersion in a step index optical fiber is given by
where
- is the fractional index of refraction
- is the refractive index of core
- is the length of the optical fiber under observation
- is the speed of light.
See also
editReferences
edit- ^ "SINGLE MODE STEP-INDEX FIBERS". Retrieved 2012-11-23.
- ^ "Fiber Optics Overview". Archived from the original on 2013-01-17. Retrieved 2012-11-23.
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This article incorporates public domain material from Federal Standard 1037C. General Services Administration. Archived from the original on 2022-01-22. (in support of MIL-STD-188).