A joint team of German researchers based out of the Fraunhofer Institute for Applied Solid State Physics (IAF) and the Karlsruhe Institute of Technology (KIT) have achieved a world record after they successfully completed a 100Gbps (Gigabits per second) data transmission over a wireless radio network at 237.5GHz. The next target is 1Tbps!
The experiment itself, which is an extension of the €2 million Millilink Project that combined the latest photonic (fibre optic) and electronic technologies, was only achieved over a distance of just 20 metres in the lab. But the teams prior outdoor test using a similar setup was able to hit 40Gbps over a more commercially attractive distance of 1km+ (i.e. between two skyscrapers).
Apparently the radio signals are generated by a photon mixer device from the Japanese company NTT-NEL, which uses two optical laser signals of different frequencies that are then superimposed on a photodiode (i.e. this is a type of photodetector that can convert light into either a current or voltage). In this case an electrical signal results (237.5 GHz) that can then be radiated via an antenna. The radio signals are later received by active integrated electronic circuits.
The radio link is designed to cope with advanced modulation formats so that it could be integrated into modern fibre optic networks in a “bit-transparent way“, which would make it useful as an alternative to the expensive process of digging up roads and fields in order to lay new high capacity fibre optic cables.
Professor Ingmar Kallfass explains:
“Our project focused on integration of a broadband radio relay link into fiber-optical systems. 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. 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.”
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 wifi world. Alternatively it might also be used for indoor transmissions using a miniaturized (compact) antenna design.
But by far the best bit of news is that the team have only just scratched the surface and are yet to test the impact of multiplexing techniques, which would in theory allow them to simultaneously transmit multiple data streams. On top of that there’s also scope for using multiple transmitting and receiving antennas, which could result in wireless transmissions that top 1Tbps (Terabit per second)!
As usual it could take years for such lab trials to reach the mainstream but it’s another promising development and one that’s well worth keeping an eye on.
The project itself is covered in more detail via Nature.