A fiber optic cable is made either of very fine glass or plastic. A single strand of optic fiber material is able to transmit around 25,000 calls simulateneously - this alone gives you an idea of how much traffic a full fiber optic cable can handle at the same time. This technology is definitely the fastest since it uses light based technology rather than wire cables or radio waves for information transmission.
The mechanisms of the fiber optic and its materials allow for the light not to leak out of the glass cable while it is traveling. The core of the cable is where the light travels. There is another layer wrapped around the outside of the core that is composed of two different types of glass that are meant to reflect the light inside the core. That way the light is not deflected outside the fiber optic core and the signal is not lost. Fiber optic cables have higher bandwidth than copper cables.