Question

Derived an expression for Numerical aperture of an optical fiber

Answer 1

For air n0 =1. Therefore, for light to be propagated within the core of optical fiber as guided wave, the angle of incidence at core-cladding interface should be greater than θ'c. ... Numerical Aperture is defined as the Sine of half of the angle of fibre's light acceptance cone.

Answer 2

Numerical aperture is defined as the sine of half of the angle of fibre's light acceptance cone.