Optical Communication At Record-High Speed

Soliton frequency combs generated in optical microresonators allow to transmit data at rates of more than 50 terabits per second – publication in Nature

Researchers at Karlsruhe Institute of Technology (KIT) and École Polytechnique Fédérale de Lausanne (EPFL) have set a new record for optical data transmission: As reported in Nature, the team exploits optical solitons circulating in silicon nitride microresonators to generate broadband optical frequency combs. Two such superimposed frequency combs enable massive parallel data transmission on 179 wavelength channels at a data rate of more than 50 terabits per second.

Optical solitons are special wave packages that propagate without changing their shape. In optical communications, solitons can be used for generating frequency combs with various spectral lines, which allow to realize particularly efficient and compact high-capacity optical communication systems. This was demonstrated recently by researchers from KIT’s Institute of Photonics and Quantum Electronics (IPQ) and Institute of Microstructure Technology (IMT) together with researchers from EPFL’s Laboratory of Photonics and Quantum Measurements (LPQM).

As reported in Nature, the researchers used silicon nitride microresonators that can easily be integrated into compact communication systems. Within these resonators, solitons circulate continuously, thus generating broadband optical frequency combs. In their experiments, the researchers from Karlsruhe and Lausanne used two interleaved frequency combs to transmit data on 179 individual optical carriers, which completely cover the optical telecommunication C and L bands and allow a transmission of data in a rate of 55 terabits per second over a distance of 75 kilometers. “This is equivalent to more than five billion phone calls or more than two million HD TV channels. It is the highest data rate ever reached using a frequency comb source in chip format,” explains Christian Koos, professor at KIT’s IPQ and IMT.

The components have the potential to reduce the energy consumption of the light source in communication systems drastically. The soliton comb sources are ideally suited for data transmission and can be produced in large quantities at low costs on compact microchips. Microresonator soliton frequency comb sources can considerably increase the performance of wavelength division multiplexing (WDM) techniques in optical communications.