I used a couple of different diameter fiber optic filament to create "Fireworks" through a 2-tier stars and stripes themed cake!

To start you have to measure the height of your cake and then measure additional length for the part that will protrude through the cake. 

Once measured shrink wrap the fiber optic cable together with as many stands as you see fit. 

Start from the top of the cake and feed it through the holes that you have designated for the fiber optics to travel.

For the light source I utilized a spinning light that came out of my table top fiber optic Christmas tree.