A fiber has n1 15 n2 149 and core diameter 50 um Consider

A fiber has n_1 = 1.5, n_2 = 1.49, and core diameter 50 um. Consider the guided ray travelling at the steepest angle with respect to the fiber axis. How many retlections are there per meter for this ray?

Solution

If a ray enters an optic fiber at a steep angle(ii), when this ray intersects the core-cladding boundary, the angle of intersection is too large. So, reflection back in to the core does not take place and the light ray is lost in the cladding.

So zero reflections.