When Light Eases the Cloud: Low-Energy Optics for Data Centers

Behind every click, every video streamed, or every artificial intelligence query, a data center works in the shadows. These infrastructures, true digital cathedrals, host thousands of servers connected by kilometers of cables. Their role is essential, but it comes at a cost: the electricity consumed by these facilities is enormous, representing several percent of global consumption.

Today, one approach is attracting increasing attention: low-energy optics, the use of light beams and photonic components to transport information with far less energy. Researchers have been exploring this path for years, and results show that optics could profoundly transform the energy equation of the cloud. And because data centers are complex technical buildings, any improvement in their digital efficiency directly impacts their overall energy performance, their architectural design, and their cooling requirements.

Why Shift from Electronics to Optics?

In classical architectures, data travels via electrical signals. This transmission mode faces two main limits:

• at high speed, electrical lines lose significant energy due to capacitive charging and discharging;

• each signal must be encoded, decoded, and resynchronized by electronic circuits, themselves energy-hungry.

  
  

The result: as traffic increases, so does the energy bill. For a data center building, this also means more heat generated, and therefore more cooling required through HVAC systems (heating, ventilation, air conditioning).

In contrast, light beams do not suffer from these constraints. As Cheng et al. (Optica, 2018) highlight, optics eliminates most losses linked to electrical charging, can transport large volumes of data over long distances, and drastically reduces per-bit dissipation. Less heat generated per bit transmitted also means less thermal load for the building, and therefore less cooling needed.

However, it is not all perfect. As Tossoun et al. (Nature Communications, 2024) note, lasers, modulators, and detectors must remain powered even at low traffic. These components consume energy constantly. This is why optical efficiency relies on smart strategies of switching on, off, and dynamic control, which directly influences the integrated energy management of the data center building.

Case Studies: Optics Put to Work

 LC/DC – Turning Off the Light to Save Energy

A notable breakthrough comes from a project called LC/DC (Laser Control for Data Centers). Researchers (Arxiv, 2021) proposed an innovative co-design between the operating system, switches, and optical lasers. Their idea: switch off redundant optical transceivers when traffic is low, while still ensuring an active path between nodes.

• Results obtained: up to 60% energy savings on transceivers, with overall gains between 9 and 27% of the data center’s total energy consumption.

• Impact on performance: only 6% additional latency.

• Concrete example: simulating real traffic from Facebook and Microsoft, they showed that about half of the network could be switched off 87% of the time without connectivity loss.

At the building level, this means less heat dissipated in server rooms, reduced pressure on cooling systems, and an architecture easier to optimize thermally.

 Silicon Photonics – Light Engraved into the Chip

Another area of innovation is silicon photonics. Here, it is no longer only about linking racks but about integrating light directly at the chip level.

According to a survey (ResearchGate, 2024), optical on-chip interconnections achieve efficiencies of 1 to 5 pJ/bit. By comparison, the best electrical interconnections consume several times more.

The benefits are twofold:

• leveraging semiconductor manufacturing processes to produce at scale and lower costs;

• enabling massively parallel processors and high-performance servers to communicate smoothly without energy bottlenecks.

By reducing heat at the source, these innovations help lower the overall thermal loads of the building, influencing HVAC system sizing and electrical infrastructure.

 Passive AWGR Networks – Efficiency and Resilience

Another study (Arxiv, 2021) explored passive optical networks. The principle: use AWGR (Arrayed Waveguide Grating Routers) that require no active power supply.

The results are striking: about 43% energy savings at the network level compared to a classical Fat-Tree architecture. This energy sobriety comes with architectural simplification for the building, since electrical and cooling requirements are reduced in technical rooms.

Between Promises and Constraints

Figures from the studies provide a clear picture of the potential:

• 60% savings on optical transceivers (LC/DC).

• Up to 27% reduction of a data center’s total energy (LC/DC).

• 1 to 5 pJ/bit for on-chip optical communications (nanophotonics).

• 43% network energy savings with passive AWGR networks.

These magnitudes show that optics can address one of the major energy expense drivers in data centers: internal connectivity. And since data centers are buildings where energy is consumed both by IT and by infrastructure (cooling, power, ventilation), optics indirectly contributes to reducing the building’s overall energy use.

Yet these promises come with constraints:

• Wake-up latency of lasers;

• Complex coordination between software and hardware;

• High cost of some photonic components;

• Insufficient standardization across vendors.

Conclusion

Low-energy optical technologies are no longer just theoretical promises. The numbers speak for themselves: 60% savings on transceivers, 43% less energy for networks, 1–5 pJ/bit in on-chip communications. These results, drawn from studies published in Optica, Nature Communications, Sustainable Computing, ResearchGate, and Arxiv, show that light can become a powerful ally in reducing the carbon footprint of digital infrastructure.

And the link with buildings is clear: less IT energy consumption means less heat to remove, resulting in leaner data center buildings, easier to certify (LEED, BREEAM, EDGE), and better aligned with sustainability strategies.

The challenge is no longer to prove feasibility, but to industrialize. By combining technological innovation, standardization, and sustainable building design, tomorrow’s data centers can be faster, more powerful, and above all more respectful of their built environment. Light, which has illuminated our lives for millennia, could soon illuminate the future of the cloud… and the buildings that host it.

Sources 

[1] Cheng, Q. et al. – Recent advances in optical technologies for data centers, Optica, 2018.

[2] Tossoun, B. et al. – High-speed and energy-efficient non-volatile silicon photonic memory based on memresonator, Nature Communications, 2024.

[3] Sharma, K. et al. – Energy-efficient and sustainable communication in optical networks, Sustainable Computing, 2020.

[4] ResearchGate (Survey) – Towards efficient on-chip communication: A survey on silicon nanophotonics and optical networks-on-chip, 2024.

[5] Arxiv (2021) – LC/DC: Laser Control for Energy-Efficient Datacenters.

[6] Arxiv (2021) – Energy-efficient optical interconnects with passive AWGR-based topologies.