In 1880 , Alexander Graham Bell and his assistant Charles Sumner Tainter created the photophone , at Bell 's newly established Volta Laboratory in Washington , DC . Bell considered it his most important invention . The device allowed for the transmission of sound on a beam of light . On June 3 , 1880 , Bell conducted the world 's first wireless telephone transmission between two buildings , some 213 meters ( 700 feet ) apart . Its first practical use came in military communication systems many decades later , first for optical telegraphy . German colonial troops used heliograph telegraphy transmitters during the Herero and Namaqua genocide starting in 1904 , in German South-West Africa ( today 's Namibia ) as did British , French , US or Ottoman signals
Herero and Namaqua genocide
Herero and Namaqua genocide
Free-space optical communication