Will a switch to light speed cut power use at data centres?

At some data centres, the next big wiring change may be less about metal and more about light. Chris Sharp, the chief technology officer at operator Digital Reality, thinks the industry is nearing the end of copper’s role inside these facilities. Not because copper is running out, but because people are looking for something better inside the server hall.

A typical 100MW data centre can use around 400 tonnes of copper. Most of that goes into power and cooling infrastructure, but up to 70 tonnes can be tied up in the servers themselves, and as much as 20 tonnes in the network wiring that links them. That last part is where the attention is now going. Those bundles of cables, carrying data as electrons, are seen by some operators and researchers as the bottleneck.

The alternative is photonics, which moves data as light through fibre. Fibre has long carried traffic over distance, but the goal now is to push it deeper into the data centre itself, including directly onto chips and other electrical components. The attraction is simple: light does not create the same heat as electricity, so less cooling is needed. Callum Littlejohns of Cornerstone Labs says that could save a lot of energy. He also says the same channel can carry multiple data streams, increasing capacity.

But this is not a neat swap of one cable for another. Peter O’Brien at Ireland’s Tyndall Research Institute says the field has spent years working through manufacturing problems, and now it is ready for broader use. Nvidia’s backing has helped, but the industry still has to work out how to build photonics cheaply at scale, with parts of the process spread across the globe and final assembly often done in packaging houses in Taiwan. Andrew Wheeler of Hewlett Packard Labs says the electrical side has already spent years getting cheaper and easier to build, test, and deploy. Photonics still has that work ahead of it.

There are also practical headaches. Optical parts may run cooler, but they still sit inside hot data centres, and they are sensitive to heat. The equipment is also harder to handle than copper: fibre dislikes tight bends, and installers will need new skills. For now, the biggest savings may come from using light only for moving data. The bigger prize, argued by Ofer Shapiro of Resolight.ai, is to keep data in the optical domain even for switching and processing. That future is further off, but the industry is clearly starting to place its bet.