Answer to Question #317036 in Optics for naji

Question

Amultimodestep-indexfiberhascoreand cladding refractive indices of 1,475 and 1.458 respectively. If it has a core radius of 30 μm and operates at a wavelength of 1250 nm.

– What should be the core radius of the fiber if it is to operate as a single mode fiber

Answer 1

Now we know that

N.A=$\sqrt{n_1^2-n_2^2}$

$$NA=\sqrt{1.475^2-1.458^2}=0.2232$$

$\lambda_c=\frac{2\pi a(NA)}{V_{max}}$

$a=\frac{\lambda_c V_{max}}{2\pi (NA)}$

$a=\frac{1250\times10^{-9}\times2.405 }{2\times3.14 \times0.2232}$

$a=2.14\times10^{-6}m$