[jaywalk]

There's no way to own a physical "slice" of fiber optic cable. The wavelengths all travel together, and there are optical splitters/combiners at each end that separate/combine the wavelengths of light. Think of them like TV and radio broadcasts. Each station broadcasts on it's own frequency (wavelength) over the shared air (fiber).

A metaphor with light would be if you had two lights, one red and one blue. If you shine them both at the same spot, you'll see purple. If you put a prism in that spot, it'll split the red and blue light back out separately. At a very high level, that's what happens with fiber optics.