For
optical fiber
An optical fiber, or optical fibre in Commonwealth English, is a flexible, transparent fiber made by drawing glass (silica) or plastic to a diameter slightly thicker than that of a human hair. Optical fibers are used most often as a means to ...
s, a power-law index profile is an
index of refraction
In optics, the refractive index (or refraction index) of an optical medium is a dimensionless number that gives the indication of the light bending ability of that medium.
The refractive index determines how much the path of light is bent, or ...
profile characterized by
:
where
and
is the nominal refractive index as a function of distance from the
fiber axis
An optical axis is a line along which there is some degree of rotational symmetry in an optical system such as a camera lens, microscope or telescopic sight.
The optical axis is an imaginary line that defines the path along which light propagat ...
,
is the nominal refractive index on axis,
is the refractive index of the
cladding
Cladding is an outer layer of material covering another. It may refer to the following:
*Cladding (boiler), the layer of insulation and outer wrapping around a boiler shell
*Cladding (construction), materials applied to the exterior of buildings
...
, which is taken to be homogeneous (
),
is the
core
Core or cores may refer to:
Science and technology
* Core (anatomy), everything except the appendages
* Core (manufacturing), used in casting and molding
* Core (optical fiber), the signal-carrying portion of an optical fiber
* Core, the centra ...
radius, and
is a parameter that defines the shape of the profile.
is often used in place of
. Hence, this is sometimes called an alpha profile.
For this class of profiles,
multimode distortion
Modal dispersion is a distortion mechanism occurring in multimode fibers and other waveguides, in which the signal is spread in time because the propagation velocity of the optical signal is not the same for all modes. Other names for this phenom ...
is smallest when
takes a particular value depending on the material used. For most materials, this optimum value is approximately 2. In the
limit
Limit or Limits may refer to:
Arts and media
* ''Limit'' (manga), a manga by Keiko Suenobu
* ''Limit'' (film), a South Korean film
* Limit (music), a way to characterize harmony
* "Limit" (song), a 2016 single by Luna Sea
* "Limits", a 2019 ...
of infinite
, the profile becomes a
step-index profile
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 refracti ...
.
See also
*
Graded-index fiber
A graded-index or gradient-index fiber is an optical fiber whose core has a refractive index that decreases with increasing radial distance from the optical axis of the fiber.
Because parts of the core closer to the fiber axis have a higher ref ...
References
*
Fiber optics
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