Figure by Yi Zheng: A chip-based frequency comb where each tooth in the comb forms its own infrared color on which data signals can be sent.

Chip-based frequency combs to increase the Internet capacity

Monday 07 Dec 20
by Tine Naja Berg


Haiyan Ou
Associate Professor, Group leader
DTU Electro
+45 45 25 63 80

What is a frequency comb?

A frequency comb is a type of laser whose spectrum consists of a series of di equally spaced frequency lines (comb). Each tooth in the comb forms its own infrared colour on which data signals can be sent.

Examples of applications:

  • Bear significant potential in multiplying the capacity of current telecommunication networks
  • Frequency combs serve as frequency gear-boxes in the most accurate and precise clocks that are based on optical atomic transitions.
  • Precision spectroscopy
  • Remote sensing and rapid absolute measurements of distance.

Horizon 2020 – FET Open

The mission of the Future and Emerging Technologies Programme (FET) is to turn Europe's excellent science base into a competitive advantage.

The FET Open supports early-stage, high-risk/high-gain, collaborative research projects based around new ideas for radically new future technologies. It focuses on cutting-edge science and unconventional collaborations.

DTU is leading a new project aiming to develop a sustainable chip-based frequency comb, which is going to improve the capacity and energy efficiency of the internet.

The exponentially increasing energy consumption of the Internet requires new approaches and innovations. Revolutionary new technologies are urgently needed to reduce the amount of energy-consuming components. At the same time, these must be able to meet the need for doubling the bandwidth of datacentre switches to keep pace with the traffic growth.

""Using a frequency comb we are able to replace thousands of standard lasers with only one in datacenters and that will save tremendous amounts of energy”"
Haiyan Ou, Associate Professor, DTU Fotonik

Now researchers from DTU Fotonik have joined forces with researchers, innovation experts and industry from Europe to develop and demonstrate a ground-breaking ultra-broadband frequency comb which is chip-based and one of the solutions to increase the network capacity using less energy.

The project is supported by Horizon 2020 FET Open with DKK 21 million.

“A frequency comb is an instrument that creates very short light ultrafast pulses using a laser and can measure wavelengths down to 15 decimal places. The high accuracy means that it can be used in, for example, atomic clocks and GPS devices, while the broad usefulness comes when using this technique to transmit data”, says Haiyan Ou, who is Associate Professor and the Coordinator in front of the Horizon 2020 project “CMOS compatible and ultra broadband on-chip SiC frequency comb” at DTU Fotonik.  

“In the Sicomb Project, we are focusing on demonstrating how a chip-based frequency comb can increase the capacity in a communications network handling data traffic beyond 100 Tb/s. Using a frequency comb we are also able to replace thousands of standard lasers with only one in datacenters and that will save tremendous amounts of energy”.

DTU Fotonik will develop the technological device and the project partners are helping to develop the chip-material and to implement the optical device into a real network to test it.

Sustainable and low-cost material
The frequency comb technique is quite new. It was introduced in its fully functioning form in 2000 and was discovered by Hall and Hänsch who were awarded half of the Nobel Prize in physics in 2005 for their contribution to the development of laser-based precision spectroscopy, including this optical frequency comb technique.

“Until now, frequency combs have been laser-based with high-energy consumption, big and expensive. Due to price, size and power consumption, their use has therefore been generally limited to laboratories. We develop an optical frequency comb on a chip-scale using the material Silicon Carbide, which has commercial material production in high volumes that has reduced prices considerably”, says Haiyan Ou.

“It will be the first time an optical frequency comb on a chip is made of the sustainable energy-efficient material silicon carbide. Compared to frequency combs made from other materials such as AlGaAs, and Lithium Niobate, silicon carbide has material sustainability advantages. It is both environmentally friendly, biocompatible, and gives extended device lifetime.  Furthermore, it is CMOS compatible meaning that it can be fabricated using the same manufacturing processes used for the traditional silicon electronics and finally this chip-based frequency comb will potentially be cheap to produce”.

Frequency combs can replace thousands of lasers
In a typical data centre, there are approximately 64 lasers which can each carry 100 gigabits per second. Each of these lasers and their components uses electricity. The ambition of the SiComb Project is to replace them with a single laser to save energy and reduce the control and monitor cost.

“The chip we will build propagates the light from the laser into the frequency comb. Each tooth in the comb forms its own infrared colour on which data can be sent, and thus one fibre cable can carry many different data signals,” says Haiyan.

Besides, increasing the capacity of network technology, the new silicon carbide-based optical chip will also have important impacts on many other scientific and engineering areas such as quantum optics, quantum computing, sensing, and imaging. This is also why innovation knowledge and transfer activity becomes an added value.

“We expect that our research also will lead to more secure and scalable integrated quantum networks based on these new optical chips. New embedded biosensors based on our new compact optical chip may also revolutionize the current way of medical diagnosis because of the biocompatibility of Silicon Carbide material,” says Haiyan.

About the SiComb project

SiComb is a 3-years Horizon 2020 FET(Future emerging technology)  Open project with 7 partners from both academic and industrial sectors who will collaborate to demonstrate the ground-breaking ultra-broadband frequency comb on a chip.

The partners are:


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