Rajeev Bansal
IMAGE LICENSED BY INGRAM PUBLISHING
Editor’s Note: An earlier version of this column appeared originally in the October 2023 issue of the IEEE Antennas and Propagation Magazine.
Robert W. Lucky (1936–2022), a pioneer in electronic communication, once wrote in IEEE Spectrum [1] that the “characterization of radio waves as invisible light interests me. I associate photons with visible light but not with radio waves. The very word ‘photons’ seems to connote visible light. In most of classical studies we deal instead with electrons—charged particles that have associated fields and, when they move, create waves. Maxwell’s equations describe it all, so there is no need to mention photons. But it is true that both visible light and radio waves are electromagnetic waves, and the associated particle is the photon.”
Electrical telegraphy (using electrons flowing down wires) was patented in the 1830s but decades before that the Swedes were already using the digital “optical telegraph” [2]. The original Grisslehamn optical telegraph was inaugurated in 1796 and was part of a chain of relay stations connecting the location to the capital. A replica was built in 2015 close to the original site and is open to the public [2]. As described in [2], the system “used a binary number system that allowed it to send messages rapidly with the 10 shutters on its roof, which could be set in 1,024 different combinations. Each station was just within view of the next. Using binoculars, an operator would copy the often coded message so that the next station could view it as well. Using this method, a message could travel through the country in minutes, where normally it would take hours or even days.”
Recently, on a trip to Washington, D.C., I found an interesting plaque (Figure 1) attached to the site of the former Franklin School on K Street, NW (now housing Planet Word, an interesting new museum devoted to languages). The plaque was placed there in 1947 by the Alexander Graham Bell chapter of the Telephone Pioneers of America. It reads: “From the top floor of this building was sent on June 3, 1880 over a beam of light to 1325 L Street the first wireless telephone message in the history of the world. The apparatus used in sending the message was the photophone invented by Alexander Graham Bell, inventor of the telephone.” Bell’s photophone was way ahead of its time; Marconi’s radio-based wireless telegraphy, as well as lasers, were all still in the future. It worked by “projecting voice through an instrument toward a mirror. Vibrations in the voice caused oscillations in the shape of the mirror. Bell directed sunlight into the mirror, which captured and projected the mirror’s oscillations toward a receiving mirror, where the signals were transformed back into sound at the receiving end of the projection. The photophone functioned similarly to the telephone, except the photophone used light as a means of projecting the information, while the telephone relied on electricity” [3].
Figure 1. The Washington, D.C. plaque commemorating the invention of the photophone by Alexander Graham Bell.
Now that electronics and optics have merged into photonics, what comes next? A recent article [4] published in iScience describes a navigation system that works based on muons. The authors report that “by utilizing the relativistic and penetrative nature of cosmic-ray muons, a completely new wireless navigation technique called wireless muometric navigation system (MuWNS) was developed. This paper shows the results of the world’s first physical demonstration of MuWNS used on the basement floor inside a building to navigate (a person) in an area where global navigation satellite system (GNSS)/global positioning system (GPS) signals cannot reach. The resultant navigation accuracy was comparable or better than the positioning accuracy attainable with single-point GNSS/GPS positioning in urban areas” [4]. Stay tuned!
[1] R. W. Lucky, “Rethinking radio: A novel changes my perception of radio waves,” IEEE Spectr., Apr. 2015. Accessed: Jul. 10, 2023. [Online] . Available: https://spectrum.ieee.org/rethinking-radio
[2] “Den optiska telegrafen (the Optical Telegraph).” Atlas Obscura. Accessed: Jul. 10, 2023. [Online] . Available: https://www.atlasobscura.com/places/den-optiska-telegrafen-the-optical-telegraph
[3] M. Bellis. “Alexander Graham Bell’s photophone was an invention ahead of its time.” ThoughtCo. Accessed: Jul. 10, 2023. [Online] . Available: https://www.thoughtco.com/alexander-graham-bells-photophone-1992318
[4] H. K. M. Tanaka et al., “First navigation with wireless muometric navigation system (MuWNS) in indoor and underground environments,” iScience, vol. 26, no. 7, May 2023, Art. no. 107000, doi: 10.1016/j.isci.2023.107000. [Online] . Available: https://www.cell.com/iscience/pdf/S2589-0042(23)01077-5.pdf
Digital Object Identifier 10.1109/MMM.2023.3303589