Fiber-optic communication is a method of transmitting data by sending pulses of light through an optical fiber. These days, the majority of data communication involves a fiber-optic connection. However, other methods of transmitting data exist, including satellites.
Flat-Earthers use the prominence of fiber-optic communication as “proof” of the nonexistence of satellites. Such a line of thinking is a fallacy of hasty generalization. Using the same “logic,” we can “prove” trains don’t exist just by showing the existence of cars.