Photonics technology poised to reduce energy consumption in data centres

The data centre industry is preparing for a significant shift in infrastructure as operators move away from traditional copper wiring in favour of photonics. This transition aims to address the substantial energy demands of modern facilities by utilising light rather than electrons to transmit data. Industry leaders suggest that this change could significantly lower the cooling requirements of data centres, thereby reducing overall power consumption. The shift is not driven by a shortage of copper, but by a strategic decision to adopt more efficient technology for internal data processing and network connectivity.

Currently, a typical data centre facility with a capacity of around 100 megawatts uses approximately 400 tonnes of copper. The majority of this metal is allocated to the electrical infrastructure required for power distribution and cooling systems. However, a significant portion is dedicated to the internal workings of the facility. Specifically, up to 70 tonnes of copper are used in the computer servers responsible for processing data, while another 20 tonnes are used for the network wiring that connects these servers. It is within this dense network of internal wiring that the industry sees the greatest opportunity for replacement with optical technology.

Chris Sharp, chief technology officer at data centre operator Digital Reality, argues that the copper wiring between central processing units and graphics processing units is a primary bottleneck for performance. He describes the current state of the industry as being at the end of the copper era for these specific applications. The proposed alternative, photonics, leverages the transmission of data via photons. While light has been used for decades in long-distance communications through optical fibre, researchers and companies are now working to extend this technology to the internal architecture of data centres. This involves intricate engineering where optical components are connected directly to electrical ones, sometimes integrated directly onto computer chips.

The primary advantage of photonics is the reduction in heat generation. Unlike electrical currents, light does not produce the same level of thermal energy during data transmission. This reduction in heat means that less energy is required to cool the data centre systems. Callum Littlejohns, deputy director of silicon photonics foundry Cornerstone Labs, notes that this can result in substantial energy savings. Additionally, photonics allows for multiple data streams to be transmitted down the same channel, increasing capacity without a proportional increase in physical infrastructure.

Peter O’Brien, head of research for photonics packaging and systems integration at Ireland’s Tyndall Research Institute, states that the technology is now ready for widespread application. He notes that while academics and commercial companies have worked with photonics for years, previous manufacturing challenges have hindered adoption. O’Brien describes the current period as a reset for the technology, aided by the support of major players such as Nvidia. However, the transition is not a simple swap. It requires integrating different engineering traditions and supply chains. Andrew Wheeler, senior vice president at Hewlett Packard Labs, points out that while the electrical side of data centre infrastructure has seen significant cost reductions through refined design and manufacturing processes, the optical side is still working to achieve similar cost efficiencies.

One of the challenges in scaling photonics is the global distribution of the manufacturing process. Final assembly is often conducted in packaging houses clustered in Taiwan. There are also engineering hurdles related to thermal management. Although optical networking devices generate less heat, other components within the data centre still create a hot local environment. Optical components are sensitive to heat, which raises reliability concerns unless strict thermal limits are maintained by operators and manufacturers. Furthermore, the installation and maintenance of optical networks require new skills. Network designers and field engineers must learn the nuances of fibre optic installation, such as the inability to take tight turns, which differs from copper wiring practices.

Ofer Shapiro, CEO of optical company Resolight.ai, argues that the full benefits of optical networking will only be realised when light is used for both data transmission and processing. His company proposes an architecture that replaces traditional electronic network switches with all-optical devices, eliminating the need to constantly convert data between photons and electrons. This would keep data in the optical domain, saving even more energy. In the immediate term, however, the focus remains on scaling up photonics manufacturing. Littlejohns suggests that the ability to reuse knowledge and equipment from electronics manufacturing will help lower costs. For instance, Cornerstone Labs uses older silicon manufacturing equipment, including tools from a former Intel production line used for Pentium 4 chips, to produce photonics components. This repurposing of existing infrastructure supports the argument that photonics can be produced at a huge scale, underpinning a wide range of future applications.