What does the Numerical Aperture (NA) of an optical fiber mathematically describe?

Answer

The range of angles over which the fiber can accept and transmit light.

The Numerical Aperture determines the acceptance cone for light entering the fiber, defining the limits within which light rays will strike the core-cladding interface at angles steep enough for TIR.

What does the Numerical Aperture (NA) of an optical fiber mathematically describe?

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