27 July 2021
ADVA Optical Networking - Energy-related challenges and opportunities of the ICT sector


By Dr. Klaus Grobe, Director Global Sustainability, ADVA Optical Networking SE, Germany

Summer 2021

Since the global ramp-up of the Internet, its throughput and the associated bitrates have been growing exponentially. This can be extracted from the most important reference for Internet throughput, the Cisco Visual Networking Index.

Main components of the Internet or ICT sector (information and communication technology) are wired and wireless networks, data centers, and end-user equipment. The networks that connect users and data centers account for ~25% of the total resulting energy consumption and associated emissions. They split into core and access parts. The core networks consist of aggregation switches, routers and fiber-optic wavelength-domain multiplexing (WDM) transport. For these equipment classes, some 80- 90% of the environmental impact are determined by the use-phase power consumption, which can be derived from lifecycle analyses. This is particularly true for the global warming potential (GWP).

Energy and emissions
The bandwidth growth leads to an increase in ICT power consumption, in particular for data centers and networks. The increasing power consumption also leads to increasing Carbon emissions.

Given the threats of global warming and also general resource depletion, the ICT environmental-impact growth must be seen critical.

ICT equipment got more powerefficient over time. However, it also had to cope with the growing bandwidths of an increasing number of bandwidth-hungry applications. For the core-network equipment (switches, routers, and WDM transponders), it has not been possible to cope with this bandwidth growth by gains in power efficiency: as a result, core-network equipment, over time, consumes more power. This is shown in Figure 1.


Power efficiency also massively grew. In Figure 1, this can be seen because all equipment shown develops toward isolines of constant and improving power efficiencies of 1000 → 0.1 W/ Gbps (Watts per Gigabit-per-second). Our latest WDM equipment, for example, can achieve an efficiency of almost 0.2 W/Gbps.

In addition to bandwidth growth, which will likely sustain over the next couple of years, we are approaching another area of challenge. The increase of energy efficiency in electronic switching and fiber-optic transport is approaching some fundamental limits in the next 20 years or so. Ultimately, for both, switching and photonic transport, this will be the so-called Shannon-von Neumann-Landauer (SNL) thermal limit, as shown in Figure 2. The SNL limit is posed by quantum physics.


The practical consequence is the end of density scaling in semiconductors. Without new, disruptive developments, the minimum switch size will stop somewhere close to 5 nm. This will have effects on future energy efficiency.

In addition, further saturation effects already became visible. As a consequence, there has been strong increase in power consumption for the highest-ranking high-performance computing machines over the last four decades (from ~150 kW around 1980 via ~700 kW in 2005 to 17 MW in 2014).

Storage equipment in data centers is facing saturation effects as well. The main media for mass storage – tape, hard-disk drives (HDD) and optical disks – show slowed-down increase in further areal density. The latter is relevant for resource efficiency. For HDDs, there is also an effect on energy efficiency.

Disruptive new developments are not clear right now. Theoretically, concepts like entropy-preserving switching or thermodynamically reversible computing can break the SNL limit, but they may not be acceptable in practice because the energy advantage comes at the cost of switching speed.

Other technologies like carbon nanotubes or biological-cell processors may allow to get closer to the SNL limit than today’s CMOS technology. However, they do not yet present mature technology.

There is one important aspect that can relax the emissions situation that results from the ICT power consumption. This aspect is sometimes referred to as Greening-by-ICT. It refers to emissions savings in sectors other than ICT that are enabled by ICT through respective digitalization. The most relevant sectors that can be significantly improved regarding power consumption and emissions are manufacturing, energy (e.g., the power grids), buildings, mobility, and agriculture. According to GeSI Smarter 2030, the carbon-saving effect on a global scale can be almost a factor of 10 higher than the ICT emissions themselves. This is indicated in Figure 3. It shows global Carbon emissions with ICT emissions and the potential Greening-by-ICT Carbon savings.


ICT networks have certain environmental impact that is currently not fully avoidable despite all attempts for maximum efficiency. However, the ICT sector has very strong potential for Carbon abatement in various other sectors. These Greening-by-ICT effects are a clear opportunity on the way toward Carbon neutrality. It is therefore likely that we need even more ICT to exploit more Greening-by-ICT.

Contact details:
Dr. Klaus Grobe
ADVA Optical Networking SE
Fraunhoferstr. 9a
82152 Martinsried, Germany
Email: KGrobe@ADVAoptical.com