Does fibre optic cable bandwidth stack over the length of the cable?
Let's say you transmit at 10 Gb/s. Then the bit period is 0.1 ns. 

The index of refraction of glass is about 1.5, so the speed of propagation through the fiber is \$c/1.5\$, or about \$200\times10^6\ \mathrm{m}/\mathrm{s}\$.

So each bit occupies about 20 mm of length, and there are about 50 bits "in flight" in every meter of fiber.

If you want to know what happens when you use the "maximum data bandwidth" of the fiber, you'll have to define what you mean by that. In practical systems, the bandwidth isn't limited by the fiber but by the transmitters and receivers at each end. The number of wavelength division multiplexing channels that can be used is limited by nonlinear behavior that occurs in the fiber when the total power (across all channels) gets too high. So even that limit depends on the sensitivity of your receivers (which determines how low you can make the power in each channel).