Technologies for 6G

KIT scientists have developed ultrafast electro-optical modulators that convert data streams from wireless terahertz to optical fiber transmission. This could be an important step on the way to 6G.

While the new mobile radio standard 5G is still being tested, researchers are already working on technologies for the next generation of wireless data transmission. 6G should enable significantly higher transmission rates, shorter delay times, greater device density and the integration of artificial intelligence.

But there are still many challenges to overcome on the way to the sixth generation of mobile communications, both in terms of the individual components and their interaction. For example, the wireless networks of the future will consist of a large number of small mobile radio cells within which large amounts of data can be transmitted quickly and efficiently. Networking these cells requires radio links that can transmit dozens or even hundreds of gigabits per second on a single channel. This is possible with frequencies in the terahertz range, which lie in the electromagnetic spectrum between microwaves and infrared radiation. A further task is to seamlessly connect wireless transmission links with fiber optic networks in order to combine the advantages of both technologies - high capacity and reliability with mobility and flexibility.

Scientists at the Institutes of Photonics and Quantum Electronics (IPQ), Microstructure Technology (IMT) and High Frequency Engineering and Electronics (IHE) at KIT and at the Fraunhofer Institute for Applied Solid State Physics IAF in Freiburg have developed a promising approach for the conversion of data streams from terahertz transmission to optical transmission. As they report in the scientific publication Nature Photonics, they use ultrafast electro-optical modulators to convert a terahertz data signal directly into an optical signal and thus couple the receiver antenna directly to a glass fibre.

In their experiment, the scientists use a carrier frequency of about 0.29 THz and achieve a transmission rate of 50 Gbit/s. The signal is then directly coupled to an optical fiber. "The modulator is based on a plasmonic nanostructure and has a bandwidth of more than 0.36 terahertz," explains Professor Christian Koos, head of IPQ and member of the IMT's collegial management. "The results show the enormous potential of nanophotonic devices for ultra-fast signal processing".

The concept demonstrated by the researchers can drastically reduce the technical complexity of future mobile radio base stations and enable terahertz connections with enormously high data rates - several hundred gigabits per second are conceivable.