Record in optical data transmission

Frequency bands in mini format achieve data rates of more than 50 terabits per second

This small chip generates optical signals that reach a transmission rate of 55 terabits per second. © JN Kemal, P. Marin Palomo / KIT
Read out

Massively Parallel Signals: Researchers have reached a new record in data transmission with light. Using a silicon nitride microresonator, they generated special light signals that can transmit more than 50 terabits of data per second over a distance of 75 kilometers - equivalent to five billion calls per second. This was possible because the data was transmitted in parallel by the 179 carrier waves of two so-called laser frequency combs.

When it comes to large amounts of data and high speeds, there is no way around optical data transmission. Usually the laser signals are transmitted by means of glass fiber, but also first attempts with a transmission through the air are already running. How high the data rate is depends decisively on the form and type of the optical signals.

Light packets without wastage

Particularly high transfer rates can be achieved with so-called solitons. These light wave packets propagate in a medium without changing their shape. Conventional laser signals, on the other hand, widen in the glass fiber with increasing running distance and thus become weaker.

Now researchers from the Karlsruhe Institute of Technology (KIT) have developed a chip that can produce many parallel soliton carrier waves at once, thereby achieving high bandwidths and high transmission speeds. This is made possible by microresonators made of silicon nitride. These integrated into a chip light sources produce light packets that circulate and overlap so that so-called frequency combs arise.

Combs of light

The frequency combs consist of a plurality of sharply demarcated spectral lines at exactly the same distances - thus forming a kind of comb of light of different wavelengths. The invention, which was awarded the Nobel Prize in Physics in 2005, not only enables highly accurate optical measurements, the massively parallel light signals can also be used for data transmission. display

The soliton frequency combs are generated by silicon nitride microresonators and used for parallel data transmission. JN Kemal, P. Marin Palomo / KIT

The big advantage: Each "prong" of such a frequency comb can transport a data signal this allows for large bandwidths. Already in 2007, researchers succeeded in scaling down the components for frequency combs to such an extent that they fit on a microchip. Now, Christian Koos of KIT and his colleagues have refined the technology to a new record in optical data transmission.

55 terabits per second over 75 kilometers

For the transmission, the researchers generated two optical frequency combs, which overlap on the chip. This results in spectral lines that allow data transmission on 179 wavelength channels at the same time and that completely cover the C and L band of telecommunications. In the lab, the researchers tested what data rate could be achieved over a transmission distance of 75 kilometers.

The result: The signals reached a data transmission rate of 55 terabits per second. "That's more than five billion phone calls or more than two million HDTV channels, " explains Koos. "It's the highest data rate ever achieved with a frequency comb source in chip format."

Faster, cheaper and more energy efficient

With this new technology, the current wave length multiplexing (WDM) process in optical communication could be significantly improved. "Our Solitonen comb sources are ideal for data transmission and can be produced inexpensively and in large numbers on compact microchips, " explains Tobias Kippenberg. In addition, the Solitonen Frequency Cameras could drastically reduce the energy consumption of communication systems.

"Powerful transceivers in chip format for future Petabit networks are thus much closer, " says Koos. (Nature, 2017; doi: 10.1038 / nature22387)

(Karlsruhe Institute of Technology, 08.06.2017 - NPO)