Not content with the 40 Gbps data speed record they achieved in an outdoor experiment, researchers affiliated with Germany's Karlsruhe Institute of Technology (KIT) topped themselves by delivering 100 Gbps of data at a frequency of 237.5 GHz over a distance of 20 meters in a laboratory.
Top, the receiver unit and oscilloscope used to record the 100 Gbps signal; bottom, radio relay transmission at 20 meters. (Photos courtesy of KIT)
The institute's researchers applied what was described as a photonic method to generate the radio signals at the transmitter, which used a photon mixer made by the Japanese company NTT-NEL. Two optical laser signals of different frequencies were superimposed on a photodiode. The resulting electrical signal--the frequency of which equals the frequency difference of both optical signals, which, in this case, was 237.5 GHz--was then radiated via an antenna. Upon transmission, the radio signals were received by active integrated electronic circuits, which were produced by the Fraunhofer Institute of Applied Solid State Physics (IAF).
"Our project focused on integration of a broadband radio relay link into fiber-optical systems," said Professor Ingmar Kallfass, who is now conducting research at Stuttgart University. "For rural areas in particular, this technology represents an inexpensive and flexible alternative to optical fiber networks, whose extension can often not be justified from an economic point of view," he added.
Kallfass said the technology could also be used within buildings. "At a data rate of 100 Gbps, it would be possible to transmit the contents of a Blu-ray disk or of five DVDs between two devices by radio within two seconds," he said.
According to Professor Jurg Leuthold, "It is a major advantage of the photonic method that data streams from fiber-optical systems can directly be converted into high-frequency radio signals."
"Due to the large bandwidth and the good linearity of the photon mixer, the method is excellently suited for transmission of advanced modulation formats with multiple amplitude and phase states," added Leuthold, who is now affiliated with ETH Zurich.
This past spring, researchers with KIT and IAF said they had achieved a wireless speed record using 240 GHz spectrum to deliver a peak data speed of 40 Gbps over a distance of one kilometer. Both the 40 Gbps and 100 Gbps speed records were achieved as part of the Millilink project, which started in March 2010 and officially wrapped up in May 2013.
"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," said Professor Thomas Zwick, head of the KIT Institute of High-Frequency Technology and Electronics.
- see this KIT release
- see this ExtremeTech article
Wireless speed record of 40 Gbps claimed by German researchers
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