Question

The refractive index of the core and cladding materials of an optical fibre is 1.46

and 1.38, respectively. Calculate the critical angle, numerical aperture and

acceptance angle at the air-fibre interface.

Answer 1

Answer

Critical angle

$\theta=sin^{-1}(\frac{1.38}{1.46}) =70.9°$

Numerical aperture

$NA=(1.46^2-1.38^2) ^{0.5}=0.476$

Acceptance angle

$\theta=sin^{-1}(0.476) =28.46°$