In
fiber optics
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 ...
, the radiation angle
is half the
vertex angle
In geometry, a vertex is an angle (shape) associated with a vertex of an n-dimensional polytope. In two dimensions it refers to the angle formed by two intersecting lines, such as at a "corner" (vertex) of a polygon. In higher dimensions there ca ...
of the cone of
light emitted at the exit face of an
optical fiber.
The cone boundary is usually defined (a) by the angle at which the
far-field irradiance In radiometry, irradiance is the radiant flux ''received'' by a ''surface'' per unit area. The SI unit of irradiance is the watt per square metre (W⋅m−2). The CGS unit erg per square centimetre per second (erg⋅cm−2⋅s−1) is often used ...
has decreased to a specified fraction of its maximum value or (b) as the cone within which there is a specified fraction of the total radiated
power at any point in the
far field.
See also
*
Guided ray
*
Numerical aperture
In optics, the numerical aperture (NA) of an optical system is a dimensionless number that characterizes the range of angles over which the system can accept or emit light. By incorporating index of refraction in its definition, NA has the proper ...
References
*
Fiber optics
Lighting
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