In 1880 Alexander Graham Bell Invented the Photophone. While his earlier invention, the telephone, uses electricity to transmit voice communications, the photophone relied on a beam of light to send sound. A person’s voice was projected through an instrument toward a mirror. The vibrations of the voice caused vibrations in the mirror. Sunlight was then directed into the mirror, where the vibrations were captured and projected back to the photophone’s receiver where they were converted back into sound.
Bell believed that the photophone was “the greatest invention [I have] ever made, greater than the telephone”. He might be right, the photophone was a precursor to the fiber-optic communication systems. The reason why the photophone didn’t take off during Bell’s time is simply that the system was useless whenever the weather was cloudy. LINK