The light doesn't really work that way.
u/Denvercoder9 mentioned that there are 8 strands of fiber in this particular cable. Each strand can host multiple wavelengths of light, that do not really interfere with each other. There are different ways of dividing up the usable frequency range; here's a site with some examples: http://www.3coptics.com/News/11.html (Remember, light has a frequency & a wavelength. Human vision covers wavelengths from around 400 nm (nanometers, the UV end) to 700 nm (the IR end)).
The beams of laser light sent down a fiber strand have a wavelength (a central wavelength), and a width. The beam essentially needs exclusive ownership of wavelength ± width. The diagrams on the linked page show how channels are separated to give each channel a set width.
So, when an entity owns a part of a cable, they own a set of wavelengths, likely one or more contiguous blocks of wavelengths, that they can use for whatever. All owners will pay (probably based on the % of wavelengths they control) for a company to operate the cable (running the stations at each end, where the wavelengths are split out on to separate fibers for each owner). The owners will also pay for another company to do repairs as needed.