Light through a cylindrical fiber-cable which has decreasing radius; one in shape of a helix 
I thought of the idea during breakfast this morning, and it has been nagging me all day - so hopefully (probably) I will find some good answers here. I'm not a physics student (economics), so please be gentle!
Suppose that you have a fibercable (or similar with $\approx$ 100% reflectivity). At the start, light initially passes through a radius $d_i$ and then travels through the cable - which is shaped as a helix - and then passes out at the end of the cable, which then has a radius $d_e$ where $d_e << d_i$. 
Basically, what will happen? Given perfect conditions (e.g. $d_e \rightarrow 0$) - shouldn't the lightbeam be intensified? 
All answers are appreciated!
 A: The great advantage of  fiber cables is that they are almost perfect waveguides, they turn corners, so a helical or whatever geometry for the cable does not affect the light within,and that is why they are useful in communications. 
Only if the diameter of the cable would change to become smaller  there would be an intensification of the light intensity. 
Think of a water pipe  in your geometry, the shape is irrelevant for the pressure, which is constant as long as the diameter of the pipe is the same.
A: You're probably thinking about how, for example, an ice skater who's spinning will spin faster when she pulls her arms in, due to conservation of angular momentum. Light won't work quite the same way.
A situation vaguely analogous to your helical light path for light would be to have light bouncing in a square path between four mirrors.  If the mirrors all moved gradually toward the center of the square, the light would be affected. The light would increase in frequency: red light would be shifted towards blue.  Blue light has more energy per photon than red light, so the circulating light would indeed increase in energy. 
However, there is a crucial difference between the moving mirrors scenario and the helical fiber scenario: in the helical fiber, light is not bouncing off of anything that's moving, so its frequency will not be shifted.  
