Foto: Bax Lindhardt

How to control the Internet’s energy consumption

Tuesday 03 Dec 19
by Morten Andersen


Niels-Kristian Hersoug
Senior Project Manager
DTU Fotonik
+45 40 60 70 68


Leif Katsuo Oxenløwe
Professor, Group Leader
DTU Fotonik
+45 45 25 37 84

The Internet’s energy consumption in numbers

One hour’s film streaming in HD quality on Netflix or another streaming service consumes just as much energy as boiling eight litres of water in an electric kettle. This is equivalent to emitting 163 grams of CO2. When four gamers play Fornite for two hours, they use 140 watt-hours, equivalent to boiling 1.2 litres of water in an electric kettle. This equals 24 grams of emitted CO2.


The INCOM project

In the project ‘Innovative Solutions for Next Generation Communications Infrastructure’ (INCOM), DTU, Aarhus University, and 12 Danish companies are working together to create the sustainable optical communication of the future.

The total budget is DKK 100 million, of which Innovation Fund Denmark contributes DKK 60 million. The last DKK 40 million are funded by partners.

The participating companies are Accelink Denmark, Bifrost Communications, Chocolate Cloud, Comcores, Danish Optical Fiber Innovation, Develco Products, Mellanox Technologies Denmark, Napatech, NKT Photonics, OFS Fitel Denmark, Telia Denmark, and Zeuxion.

The Internet is indispensable, but we need to get the CO2 emissions that result from increasing data transmissions under control. The answer is more energy-efficient optical systems.

Faster, cheaper, and more powerful. In the last few decades, this has been the mantra for the fast-paced development of optical fibres that transmit data at the speed of light via the Internet. But a new issue has become relevant: climate considerations. The Internet’s energy consumption must be controlled.

“It’s impossible to expand the supply of renewable energy at the same rate as energy consumption for data communication grows. That is why the current situation is unsustainable. But the solution is not to ban Fortnite or the downloading of films. Fortunately, our research shows that it’s possible to significantly reduce energy consumption per transported amount of data through new breakthroughs in optical transmission,” says Niels Hersoug, Senior Project Manager at DTU Fotonik. He is heading the INCOM project (Innovative Solutions for Next Generation Communications Infrastructure), where DTU and Aarhus University—in collaboration with 12 Danish companies—are working to create the sustainable, energy-efficient optical communication of the future.

Even more data with IoT and 5G

If we gathered all the content of all the books and other writings created from the birth of mankind up to the year 2000, it would still not match the amount of data being transmitted around the globe on a single random day in 2019. This huge amount of data transmission requires energy. More specifically, data transmission represents 8-9% of the world’s overall electricity consumption. This equals about 2% of the world’s CO2 emissions.

Add to this that data transmission hasn’t topped yet. The Internet of Things (IoT), where machines communicate directly with each other using the Internet, is still only in its infancy. When the IoT is rolled out in full, there will be an enormous need for data transmission between machines. The next generation of mobile communication, 5G, will also add to the amount of transmitted data.

So, something has to be done. More specifically, we must focus on optical transmission, which is fundamentally much more energy efficient than electronic communication (see explanation page 20). Indeed, optical transmission has long since displaced electronic transmission on the Internet’s ’backbone’—that is, the ’main roads’ where the really large amounts of data are transferred.

Conversions require energy

In other words, we use light to transfer data at longer distances, while electrons continue to carry data at shorter distances, such as in our computers and mobile phones. As the optical components are optimized, however, they will become the ideal solution for all data transmission. Partly because they can be very energy efficient in themselves, and partly because it will be possible to get rid of part of the conversion necessary to shift between electronic and optical transmission today. Data is typically born electronically—e.g., in a computer or mobile phone—and then converted to optical signals, transmitted optically, and re-converted back to electronic form. Each conversion requires energy.

In other words, the Internet will become more sustainable as more transmission and signal processing will be in optical form.

At the same time, the INCOM project’s aim is also to reduce energy consumption in the transmission that already happens optically.

“Research here in the department has shown that it’s possible to dramatically improve optical transmission,” says Niels Hersoug.

Strong optical environment in Denmark

The perspective of optical transmission was highlighted at DTU Fotonik in 2012. Here, a research group lead by Professor Leif Katsuo Oxenløwe set the world record by transmitting 661 Tbit/s through a single fibre. This is equivalent to transmitting the world’s entire data communication through a single fibre.

“There is no need to do this in practice, of course. But the record illustrates the potential of optical communication. There is even a great deal of scope for transferring much larger amounts of data than today without a corresponding increase in energy consumption,” says Niels Hersoug and emphasizes the growth potential of Danish companies in the industry:

“Much stems from the optical environment built around the NKT Group from the mid-1980s and onwards. The company itself founded several subsidiaries and spin-out companies. At the same time, a strong academic environment emerged, including here at DTU. In this way, there’s a special Danish chance to develop solutions in this area, although it is inherently a global issue.”

Why optical transmission has a low energy consumption

Imagine that you are shining a flashlight down a dark corridor. As long as the corridor is straight, it works just fine, but what if you want your flashlight to shine down another corridor around a corner? The solution must be to place a mirror at the end of the first corridor. This is precisely what fibre-optic communication is about. Except the mirror is invisible to us—it is placed within the fibre.  It is possible to design the fibre so that the light is reflected inside it and can continue around bends.

In fibre-optic transmission, a laser source rather than a flashlight emits near-infrared electromagnetic waves—light pulses—with a fixed wavelength. When the fibre design is correct in relation to the light’s wavelength, it is possible to achieve a so-called full inner reflection, which means that the light wanders through the fibre without the loss experienced in electronic data transmission.

The story does not end here, however, because even with full inner reflection, there is a slight weakening of the light’s strength as the distance gets longer. Therefore, it is necessary to insert amplifiers into very long optical cables.

This is where some of the energy consumption takes place. It also takes place at two other points in the cables: firstly, in the transmitter that generates the light pulses and simultaneously encodes them with the data to be transmitted; second, in the unit that receives and decodes the signals at the other end.

So, regardless of the very limited loss in optical cables, it naturally consumes a certain amount of energy. But the consumption is on a much smaller scale than electronic transmission.

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