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Question
The core diameter of multimode step index fibre is 50 μm.The numerical aperture is 0.25. Calculate the number of guided modes at an operating wavelength of 0.75 μm.
Solution
d = 50 x 10-6 m
N.A = 0.25
λ = 0.75 x 10-6 m
`V = (πd)/λ x N.A`
`= (π x 50 x 10^(−6))/(0.75 x 10^( −6) `
= 52.36
`Nm = (V^2)/2`
= 1370.8
= 1370
| Number of modes = 1370 |
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