Question

Calculate the V number of an optical fibre having numerical aperture 0.25 and core diameter 20 μm, if its operating wavelength is 1.55 μm. 

Answer 1

NA = 0.25
Core diameter = 20 μm
λ0   = 1.55 μm
Formula : V = ᴨd / λ0 × NA
V = 3.14 ×  20 × 10^-6 /1.55 × 10^-6 × 0.25
V = 10.13