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Numerical aperture is commonly used in microscopy to describe the acceptance cone of an objective (and hence its light-gathering ability and resolution), and in fiber optics, in which it describes the range of angles within which light that is incident on the fiber will be transmitted along it.
A high numerical aperture allows light to propagate down the fiber in rays both close to the axis and at various angles, allowing efficient coupling of light into the fiber. However, this high numerical aperture increases the amount of dispersion as rays at different angles have different path lengths and therefore take different amounts of ...
The numerical aperture of a multimode optical fiber is a function of the indices of refraction of the cladding and the core: Diagram showing how the light refracts at the core/cladding interface. With the angle of refraction being dependent upon the difference in index of refraction, n, of core and cladding.
In telecommunications, launch numerical aperture (LNA) is the numerical aperture of an optical system used to couple (launch) power into an optical fiber. LNA may differ from the stated NA of a final focusing element if, for example, that element is underfilled or the focus is other than that for which the element is specified.
In an optical fiber, the normalized frequency, V (also called the V number), is given by = =, where a is the core radius, λ is the wavelength in vacuum, n 1 is the maximum refractive index of the core, n 2 is the refractive index of the homogeneous cladding, and applying the usual definition of the numerical aperture NA.
The amount of optical power launched into a given fiber by a given transmitter depends on the nature of its active optical source (LED or laser diode) and the type of fiber, including such parameters as core diameter and numerical aperture. Manufacturers sometimes specify an optical power budget only for a fiber that is optimum for their ...
Ball lenses are often used in fiber optics. Due to their short focal lengths and the subsequently small waist diameters they produce in a laser beam, they are ideally suited to focus nearly all of the light from a laser into an optical fiber core. The numerical apertures of the fiber and lens need to match. The fiber can usually be placed in ...
The three-dimensional point spread functions (a,c) and corresponding modulation transfer functions (b,d) of a wide-field microscope (a,b) and confocal microscope (c,d). In both cases the numerical aperture of the objective is 1.49 and the refractive index of the medium 1.52.