Answer : 3. "fiber"
Explanation :

It seems there might be a confusion in your question. If you are referring to the technology used for transmitting data using modulated light, the term you are looking for is "fiber optic cable" or simply "fiber." Fiber optic cables are thin, flexible strands of glass or plastic that transmit data as modulated light pulses. They are widely used for high-speed data transmission over long distances due to their ability to carry large amounts of data with low attenuation and high bandwidth capabilities.