It seems as if someone posts a new world record for wireless data transmission speeds every few weeks--usually achieved by going to higher and higher frequencies. This time researchers working on the “Millilink” project, funded by the Fraunhofer Institute for Applied Solid State Physics and the Karlsruhe Institute of Technology managed to transmit 100 Gbps over a distance of 20 meters at 237.5 GHz in lab settings. Previous project experiments had achieved data rates of 40 Gbps at distances of more than 1 km.
What I found most interesting about the experiment was the method used to generate the 237.5 GHz signal. It used the latest photonic and electronic technologies to generate RF by using an ultra-broadband “so-called photon mixer” made by Japanese company NTT-NEL. Signals of different frequencies produced by an optical laser are superimposed on a photodiode, generating an RF signal that’s the difference between the two laser frequencies--the same concept used in superhetrodyne radios.
In this experiment, the 237.5 GHz RF signal generated by optical frequency difference was radiated by an antenna.
In describing the earlier tests with 40 Gbps data rates, Professor Thomas Zwick, head of the KIT Institut für Hochfrequenztechnik und Elektronik (Institute of High-Frequency Technology and Electronics), observed: “The long transmission distances in 'Millilink' were reached with conventional antennas that may be replaced by fully integrated miniaturized antenna designs in future compact systems for indoor use.”
Swen König from the KIT Institute of Photonics and Quantum Electronics (IPQ), who conceived and conducted the recent world-record experiment, added: “By employing optical and electrical multiplexing techniques, i.e., by simultaneously transmitting multiple data streams, and by using multiple transmitting and receiving antennas, the data rate could be multiplied. Hence, radio systems having a data rate of 1 terabit per second appear to be feasible.”
Additional information and photos of the laboratory setup are available in the KIT press release World Record: Wireless Data Transmission at 100 Gbit/s.
Mark Jackson, in his article UPD Scientists Hit 100 Gbps Wireless World Record to Aid Rural Broadband describes possible uses of the technology: “It’s perhaps best to think of this as an ultra-fast alternative to the more traditional direct line-of-sight style Microwave links, which means that it would be good for carrying capacity but not necessarily ideal for connecting individual homes. One of the reasons for that is due to the use of a high-frequency signal at 237.5GHz, which would struggle to penetrate through walls like its lower frequency counterparts in the mobile broadband and Wi-Fi world. Alternatively it might also be used for indoor transmissions using a miniaturized (compact) antenna design.”
Doug Lung is one of America's foremost authorities on broadcast RF technology. He has been with NBC since 1985 and is currently vice president of broadcast technology for NBC/Telemundo stations.
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