Describe the numerical aperture in the optical fibre.

Numerical Aperture:

The numerical aperture is described as the sine of the acceptance angle. Therefore,

Numerical Aperture (NA) = sin θ₀ = (√(n²₁ - n²₂))/n₀

Numerical aperture is a measure of the amount of light which can be accepted through a fibre. When the light ray launching zone is air medium, n₀=1 then,

Numerical Aperture (NA) = sin θ₀ = √(n²₁ - n²₂)

After that, the numerical aperture depends only onto the refractive index of the core and the cladding. Value ranges of this from 0.13 to 0.50. A huge numerical aperture means that a fibre will accept huge amount of light by the source.