After inventing the telephone, bell continued his experiments in communication, which culminated with the photophone transmission of sound on a beam of light, a precursor of today's optical fiber รขโ‚ฌยฆ In june, bell demonstrated the telephone for sir william thomson (baron kelvin) and emperor pedro ii of brazil at the centennial exhibition in philadelphia. On july 9, 1877, bell, hubbard, sanders, and รขโ‚ฌยฆ

In 1880, bell patented the photophone, which รขโ‚ฌยฆ