Data Centers Look to Light Speed for Energy Savings and Capacity

Data centers, the powerhouses of the digital age, are on the cusp of a significant technological shift, moving away from copper wiring towards photonics, which uses light to transmit data. This transition promises substantial energy savings and increased capacity, addressing two critical challenges facing the industry.

Experts suggest that copper, a metal crucial for electrical infrastructure and cooling systems within data centers, may soon be used less. A typical 100MW data center can require up to 400 tons of copper. A significant portion of this, up to 70 tons, is used in the computer servers, with an additional 20 tons dedicated to network wiring connecting these servers. It is this network wiring, often a complex web of cables, that is a prime target for replacement.

The Promise of Photonics

"The wires between these GPUs, CPUs, and all this compute are what's slowing us down," says Chris Sharp, chief technology officer at data center operator Digital Reality. "I think we're at the end of copper."

The alternative gaining traction is photonics, a technology that utilizes light (photons) instead of electricity (electrons) for data transmission. While light has long been used for long-distance communication via fiber optics, researchers and companies are now aiming to extend its application within the data center itself. This involves intricate engineering to connect optical components directly to electrical ones, sometimes even on the computer chips themselves.

A major advantage of photonics is its minimal heat generation compared to electricity. "You can save so much energy," notes Callum Littlejohns, deputy director of silicon photonics foundry Cornerstone Labs. Less heat means reduced energy demand for cooling systems, a significant operational cost for data centers. Furthermore, photonics can enable multiple data streams to be transmitted through a single channel, thereby increasing overall capacity.

Overcoming Manufacturing Hurdles

Peter O'Brien, head of research for photonics packaging and systems integration at Ireland's Tyndall Research Institute, states that while academics and commercial entities have been developing photonics for years, manufacturing challenges have slowed its widespread adoption. "What's happening now with optics and photonics is there's kind of a reset," he says, indicating a readiness for broader application. The backing of AI chip giant Nvidia is seen as a significant boost for the technology.

However, the transition is not a simple plug-and-play replacement. It requires integrating different engineering disciplines and 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, highlighting the industry's established expertise with copper. "But he says, the industry is still working out how to bring the cost down."

Manufacturing processes for photonics are currently distributed globally, with final assembly often occurring in packaging houses concentrated in Taiwan. Technical challenges also persist. While optical networks generate less heat, other components within a data center can still create high local temperatures. Optical components are particularly sensitive to heat, raising reliability concerns if strict thermal limits cannot be maintained by data center operators and equipment manufacturers.

Furthermore, while optical networks can transmit data at nearly the speed of light, their installation and maintenance still require human intervention and new skill sets. "With fibre, You can't take tight turns. There are little nuances on how to structure that," Sharp notes, emphasizing the need for specialized knowledge in installation and servicing.

Future Integration and Scalability

The full benefits of optical networking, according to Ofer Shapiro, CEO of optical company Resolight.ai, will be realized when light is used not only for carrying data but also for processing it. His company is proposing an architecture that replaces traditional electronic network switches with all-optical devices, arguing that the constant conversion between photons and electrons is inefficient. This would allow data to remain in the optical domain, further conserving energy.

In the more immediate future, efforts are focused on scaling up photonics manufacturing. Littlejohns points out that the industry can leverage decades of experience in electronics manufacturing to help reduce 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."

Interestingly, photonics components are often larger than the silicon components used in computer chips. This allows companies like Cornerstone to repurpose older silicon manufacturing equipment, some dating back to the production of Pentium 4 chips in the early 2000s. This reusability of existing infrastructure, combined with established manufacturing knowledge, provides a pathway toward cost-effective, large-scale production of photonic technologies.