Answer Happy

For a graded index fibre, the refractive index profile can be expressed as: my 1-2018 r<a n(r)= in V1 -2A = n, r>a where n, is the refractive index at the core axis, n, is the cladding refractive index, a is characteristic index profile, a is the core radius, and A is the relative refractive index. A graded index fibre with a cladding refractive index of 1.445 has a of 1.9 and a relative refractive index difference of 1.5%. (i) For a fibre with a core diameter of 45 um, estimate the number of guided modes propagating along the fibre given that the light has a wavelength of 1.56 um. [5 Marks] (ii) If the fibre is a step-index fibre with the calculated n, and nz, determine the maximum core diameter when using as a single-mode fibre at wavelength 1.3 um.