German researchers have set world record for wireless data transmission at 100 gigabits per second by using a 237.5GHz carrier and photonic mixing over a 20m distance.
Carried as shared professorship funded by the Fraunhofer Institute for Applied Solid State Physics (IAF) and the Karlsruhe Institute of Technology (KIT), the "Millilink" project was financed by Federal Ministry of Education and Research (BMBF) under the 'Broadband Access Networks of the Next Generation' programme.
With support from Siemens, Kathrein, and Radiometer Physics, both research institutes carried out the study, which was mainly concentrated on integrating wireless or radio links into broadband optical communication networks for faster internet accessing capability in rural areas.
Prof. Ingmar Kallfass said that the project focused on integration of a broadband radio relay link into fibre-optical systems.
"For rural areas in particular, this technology represents an inexpensive and flexible alternative to optical fibre networks, whose extension can often not be justified from an economic point of view," Kallfass said.
"At a data rate of 100 gigabits per second, it would be possible to transmit the contents of a blue-ray disk or of five DVDs between two devices by radio within two seconds only."
During the experiment, scientists applied a photonic process to generate the radio signals at the transmitter and afterwards the completely integrated electronic circuits were deployed in the receiver.
The transmitter generates the radio signals through NTT-NEL's ultra-broadband photon mixer, which takes two light signals of different frequencies emitted by lasers, with the frequency difference of both optical signals resulting in the 237.5GHz electrical signal, while the millimetre-wave electrical signal is transmitted via an antenna.
Prof. Jurg Leuthold said it is a major advantage of the photonic method that data streams from fibre-optical systems can directly be converted into high-frequency radio signals.
"This advantage makes the integration of radio relay links of high bit rates into optical fibre networks easier and more flexible," Leuthold said.
"In contrast to a purely electronic transmitter, no intermediate electronic circuit is needed.
"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.
"This will be a necessity in future fibre-optical systems."
In May 2013, researchers had successfully transmitted data at a rate of 40 gigabits per second and transmission distances of more than 1 km using a purely electronic system.
KIT Institut für Hochfrequenztechnik und Elektronik head, Professor Thomas Zwick said: "The long transmission distances in 'Millilink' were reached with conventional antennas that may be replaced by fully integrated miniaturised antenna designs in future compact systems for indoor use."
However, the current data rate can be increased further by employing optical and electrical multiplexing techniques, as well as through the use of multiple transmitting and receiving antennas, according to KIT Institute of Photonics and Quantum Electronics (IPQ)'s Swen König.
"Hence, radio systems having a data rate of 1 terabit per second appear to be feasible," König said.