Alexander Graham Bell and Photophone

Photophone, which was developed by the legend Alexander Graham Bell and his assistant Charles Sumner was the predecessor of the current fiber optic communication. When we say predecessor, we do nto intend to say that the development of current fiber optics started exactly from development of photophone. Directions in scientific research and development had moved in other directions than towards optical at least for several decades after invention of photophone. Charles Sumner was assistant of Bell.

Photophone was invented in 1880 at Volta Laboratory, which was established by Alexander Graham Bell. Bell considered the invention of Photophone as his most significant invention. With Photophone, Bell was able to demonstrate sound transmission using light beams. The same year, Bell demonstrated world’s first wireless communication. He selected two building to conduct the experiment one of which was Franklin School in Washington and the other was his own laboratory. From the top of School building, Bell transmitted the first wireless telephone message using his newly developed photophone to his lab, which was around 213 meters. That was in June 3, 1880 and the date found its place in history especially for those working in optical and wireless communication.

Somner, who was assisting Bell was an expert in assembling mechanical parts. He extended his support to realize what Bell had in mind. Though it may seem preliminary, the idea of sending sound signals along with light was really cool. isn’t it?. Bell believed that the photophone was his most important invention.

Bell used sunlight for his experiment with first photophone. At the transmitter end, he used a mirror that vibrated in tune with the sound vibrations. He directed the sunlight to that mirror. The mirror reflected the sunlight. Since the mirror vibrated due to the sound vibrations, the light also got affected. Bell’s device allowed the transmission of sound on a beam of light.


At the receiver end, bell transformed the vibrating light back to the sound waves. The functions of the first photophone were similar to the functions in telephone. Sound energy was converted to another form of energy (light) at the transmitter end and at the receiver end that energy (light) was converted back to the sound energy. The difference between telephone and photophone was that the latter used light as a means for sending information instead of electricity.

The idea is still utilized in free space optics, where light energy is used to transmit information. People could not recognize the value of Bell’s photophone during his life. Thinking in this modern era, we can find a number of drawbacks in his invention such as interference of light by outside environments and weather factors. No invention in human history has been unnecessary. All inventions helped mankind to move forward by encouraging others to modify or deviate from the original invention. Development of optical fibers were also not an exception.

The photophone and method of transmitting voice in the open air encouraged researchers to find more secure and more reliable medium for the light to propagate. Later we saw the birth of optical fibers. These days, we experience the power of optical fibers and fiber optic technology in our daily life.


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