Numerical Apperture of Fiber Optic Cable

Numerical Aperture of Optical Fiber Cable

Tags: Numerical Aperture of Optical Fiber, Numerical Aperture of plastic fiber cable, Theory of Numerical Aperture of Optical Fiber Cable, Procedure for Numerical Aperture of Optical Fiber Cable, Tabular column of Numerical Aperture,, Formula for Numerical Aperture
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Numerical Aperture of Optical Fiber Cable


To Study the Numerical Aperture of optical plastic fiber cable.

Apparatus Required

  • Fiber Optics Light Emitting Diode Module - 01
  • Plastic Fiber cable 1 meter - 01
  • Numerical Aperture Setup - 01
  • Adapter +12V/ DC - 02
  • Patch Chords - 04


In fiber 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 property that it is constant for a beam as it goes from one material to another provided there is no optical power at the interface. The exact definition of the term varies slightly between different areas of optics. 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 cone of light accepted into the fiber or exiting it.


  • Connect +12V adapter LED module.
  • Switch (sw1) ON LED Module
  • Connect P1 and P6 test point, P2 and P7 test point using patch chord.
  • Keep pot meter at maximum position.
  • Connect the fiber cable one end to LED module another end to Numerical Aperture setup.
  • Numerical Aperture is,

    R = radius of circle
    D = distance of cable
  • Note down the readings radius(R) in different distance(D) and calculate NA,


         (D)in mm


       (R) in mm

    Numerical Aperture





  • Find out the Average NA in the following table.
  • For the typical plastic fiber cable NA = 0.5 to 0.6


Thus the Numerical Aperture of plastic fiber cable was calculated.

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