Reading an alternative reality novel I came upon a reference to communications via a device called a Photophone.
This was real, it converted voice into a beam of light.
Alexander Graham Bell and his assistant Sumner Tainter invented it in 1880. Bell claimed it was his greatest invention.
I can't add the relevant Wikipedia URL, so here's a shortened version using an app called Shorten URLs.
https://shrtm.nu/pZW