Optical fiber is an optic cable made by drawing glass or silica,
that send signals using light. We all know that the speed of light is the fastest speed in the universe.
This is a big advantage, for the speed of the data transferring. Is not just the speed but also the bandwidth. The bandwidth of an optical fiber is many times bigger compared to other cables, like coaxial cable or Twisted pair, etc.
Another big advantage of optical fiber is that it does not interfere with electricity or other factors of nature, it means that the loss of signals from outside factors is 0. In this way, the signal can travel over many kilometers without losing the signal.
Today Optic Fiber is used almost in every home, business, and network infrastructure all over the world.
Big Companies like Verizon, T-Mobile, etc, have created an under ocean network that connects continents to each other using fiber. This type of fiber is a high-quality fiber, is a little bit complicated how it works. All continents are interconnected with a lot of fibers, and in this way, it makes possible a really fast speed of internet access for all peoples.
On this link Submarine Cable Map you can see all optic fibers that are under the oceans and sees over the world, and how are countries connected to each other on the internet.