Fiber optics are an important part of our modern internet. In these fibers, two

Question

Fiber optics are an important part of our modern internet. In these fibers, two different glasses are used to confine the light by total internal reflection at the critical angle for the interface between the core (ncore = 1.5 ) and the cladding (ncladding = 1.455).

Numerically, what is the largest angle (in degrees) a ray will make with respect to the interface of the fiber max, and still experience total internal reflection?

Suppose you wanted the largest angle at which total internal reflection occurred to be 'c = 5 degrees. What index of refraction does the cladding need if the core is unchanged?

Explanation / Answer

n= 1/sin(c)---(A) where n-refractive index and c - critical angle

for > c total internal happens.c is the minimum agle total internal happens. is measured from the perpendicular to the surface. So, the maximum angle(measured from the surface) total internal happens= c

refractive index of the surface relative to core= 1.5/1.455 = 1.03

From (A) , sin(90-max)= 1/1.03; max =13.860

If the 'c = 5 then as in above condition

sin(90-'c) =1/ n' ; n' relative refractive index

n'= 1.004

since n'=1.5/ nc ; nc-refractive index of cladding

nc= 1.49

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