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

Will a shift to light speed reduce power consumption in data centres?

Data centres consume huge quantities of copper in their electrical and data systems. “I think we’re at the end of copper,” says Chris Sharp, chief technology officer at data centre operator Digital Reality.

He is not suggesting that copper is running out. Rather, Sharp and many others in the data centre sector believe it will be used less.

Data centres rely on vast amounts of the metal: about 400 tonnes, external will go into a typical facility of around 100MW (data centre size is measured in megawatts, a unit of electrical power).

Most of that copper is used in the electrical infrastructure required to power the datacentre and in cooling systems. But up to 70 tonnes is used by the computer servers that handle data processing in that 100MW facility.

Meanwhile, up to 20 tonnes is used for the network wiring that links those computer servers together.

It is in this spaghetti-like wiring, snaking through a data centre, that copper is being targeted for replacement.

“The wires between these GPUs, CPUs, and all this compute are what’s slowing us down,” says Sharp.

Data is moved around data centres as electrons, which travel efficiently through copper wiring.

Many believe there is an even better method: using light in the form of photons.

Light has been used for decades for long-distance communications over optical fibre — the data for this article probably travelled through a fibre optic cable at some point.

But researchers and companies want to extend fibre’s use into the data centre itself.

That requires intricate engineering, with optical components connected directly to electrical ones, sometimes on the computer chips themselves.

The technology is known as photonics, and its major advantage is that light does not create the heating effects of electricity. Less heat means less energy is needed to cool data centre systems.

“You can save so much energy,” says Callum Littlejohns, deputy director of silicon photonics foundry Cornerstone Labs.

, but could make them a bit less energy hungry.

Littlejohns also notes that multiple data streams can be sent down the same channel to increase capacity.

Peter O’Brien, head of research for photonics packaging and systems integration at Ireland’s Tyndall Research Institute, said academics and commercial companies have been working with photonics for years, but the technology has faced several manufacturing challenges.

Now, O’Brien says, the technology is ready to move from the lab into widespread use.

“What’s happening now with optics and photonics is there’s kind of a reset,” he says.

It helps that AI chip giant Nvidia has backed the technology.

But moving to photonics is not a simple swap, because it brings together different engineering traditions and different supply chains.

“We’ve really gotten good at bringing the cost down on that electrical side, how to design it, how to manufacture it, how to test it, how to deploy it,” says Andrew Wheeler, senior vice president at Hewlett Packard Labs.

But he says the industry is still figuring out how to reduce the cost.

Part of the challenge is that different parts of the manufacturing process are spread across the globe. For instance, final assembly is carried out in so-called packaging houses, which are concentrated in Taiwan.

Engineering hurdles remain. Optical networking devices may produce far less heat, but other components inside a data centre still make the local environment hot.

That is a problem for optical components, which are highly sensitive to heat, Wheeler explains. This creates reliability concerns unless data centre operators and equipment makers can stay within strict thermal limits.

And while optical networks can carry data at — almost — the speed of light, installing and maintaining them will still happen at human speed. Network designers, field support engineers and installers all need to learn new skills for installation and servicing.

For example, Sharp says, with fibre, “You can’t take tight turns. There are little nuances on how to structure that.”

Fibre optic cables produce very little heat compared with copper wires.

Ultimately, the advantages of optical networking can only be fully achieved when light is used not just to carry data, but to process it too, says Ofer Shapiro, CEO of optical company Resolight.ai.

The company is proposing an architecture that would replace traditional electronic network switches, which control communications between servers, with all-optical devices.

He argues that it makes no sense to keep converting data from photons to electrons and back to photons.

Optical interconnects between computer chips and network elements would keep data in the optical domain, saving even more energy, Shapiro argues.

But that is for the future. More immediately, companies are still working to scale up photonics manufacturing.

Littlejohns says this ability to reuse knowledge gained from electronics manufacturing will ultimately help bring down the cost of photonics.

“We know we can make it huge scale, so that’s why it’s such an interesting technology, because it can underpin many applications.”

Photonics components are generally larger than silicon components used in computer chips.

Counterintuitively, this means organisations like Cornerstone can repurpose older silicon manufacturing equipment used for earlier generations of processors.

One of Cornerstone’s manufacturing tools comes from a former Intel production line used to make Pentium 4 chips released at the turn of the century.

Littlejohns says this ability to reuse knowledge gained from electronics manufacturing will ultimately help bring down the cost of photonics.

“We know we can make it at a huge scale, so that’s why it’s such an interesting technology, because it can underpin many applications.”