A good introduction on light propagation mode

[ian2015]

Hi,
Can anyone explain or point to a good introduction in simple terms the concept of 'light propagation mode'?
I am in my final year at high school and need to write a research report on how optical fiber communication systems work. The report needs to include some contents beyond what is taught in current school curriculum. However, I really struggle to understand the concept of 'light propagation mode in fiber' and its importance in communication using optical fiber. All the articles I found mentioned the concept using electromagnetic wave theory and use complicated maths which is beyond my current knowledge. Any kind people can help me? I am getting desperate as I spent a lot of time trying to understand the concept and still very confused.

Many thanks,
Ian

 

[blue_leaf77]

Propagation mode is term used to describe solution of dispersion relation describing the medium in which light propagates. For the simplest case is light propagation in free space, the propagation modes in that case are plane waves and the dispersion relation is $k(\omega) = \omega /c$. Those complicated looking expressions of propagation mode in an optical fiber is of course the solutions of dispersion relation for optical fiber.