"Fiber-optic" is just a piece of GLASS with the thickness of a hair ! Glass is an insulator, and fiber-optic can't carry electrical current.
If you have an electronic signal ... like voice, music, video, bank data, a dental X-ray, a cellphone call, a credit card charge, vital signs from a patient in an ambulance, 20 TV channels to go up to a satellite ... it has to be changed into a form that can travel through optical fiber.
The electronic signal is connected to a tiny tiny light bulb, or an LED, or a LASER diode, and it makes the light blink in time to the electronic signal. That LIGHT shines into one end of the optical fiber, and travels several miles through the glass. At the other end, it's detected by a photocell, and it gets turned back into an electronic signal again.
Where the question says "... a blank ..." up above, it's "... a light ..." .
