You are more familiar with radiowaves, microwaves, and TV signals.
Visible light is also electromagnetic radiation and can be used to transmit a signal.
It is a whole new technology called fiber optics. A discussion of this laboratory can be found in the Exploratorium Science Snackbook. By using an LED instead of a flashlight bulb, we can get a cleaner signal. Unlike incandescent light bulbs, the LEDs have a directional polarity. You must connect the positive and negative leads to them correctly, or they will not work.