Microsoft: Digital Innovation in Data Centre Connectivity

The cables running through the world's data centres have long operated at the upper limits of what physics permits. Laser-driven fibre optic links consume significant power and are sensitive to temperature fluctuations and particulates. Copper cabling, reliable and fast, cannot extend beyond roughly two metres at high data volumes. As AI workloads multiply and cloud demand intensifies, those constraints are becoming harder to engineer around.

Microsoft Research's lab in Cambridge has developed a cabling system it believes can change the status quo.

Using commercially available MicroLEDs and imaging fibre – the kind already deployed in medical endoscopy equipment – the team has produced a link technology that, based on lab tests and deployment estimates, is expected to use around 50% less energy than mainstream laser-based optical cables. Commercialisation with industry partners is anticipated for late 2027.

A new approach to moving data

Paolo Costa, Partner Research Manager at Microsoft and lead researcher on the project, describes the core principle in terms that make the physics intuitive. Laser-based fibre delivers data in pulses across a small number of channels – what Paolo calls the "narrow and fast" approach. The MicroLED system, by contrast, uses thousands of independent channels to transmit data in patterns comparable to QR codes. The "wide and slow" approach, as Paolo characterises it, carries equivalent data volumes across a broader front, analogous to a wide, slow river moving the same water as a narrow, fast stream.

The imaging fibre that makes this possible had an unlikely origin. "Imaging fibre looks like a standard fibre, but inside it has thousands of cores," says Paolo. "That was the missing piece. We finally had a way to carry thousands of parallel channels in one cable." The technology extends the reach of MicroLED links to tens of metres, bridging the gap between copper's short-range precision and the longer but more temperamental reach of laser-based fibre.

The project reached a significant milestone when Microsoft completed a proof of concept with MediaTek and other suppliers to miniaturise the system into a transceiver compatible with existing data centre equipment. That device – roughly the size of a large thumb – contains lenses, photodiodes and signal processing hardware that would have occupied a full laboratory bench only a few years ago.

From laboratory bench to data centre floor

Doug Burger, Technical Fellow and Corporate Vice President at Microsoft Research, places the development in context. "The early concept of using LEDs to send data more cheaply – and with lower power – than both copper and fibre optics once seemed like a fantasy," he says. "This breakthrough has the potential to change nearly every aspect of computing infrastructure … starting with high-bandwidth optical cables."

MicroLED is one of two networking technologies Microsoft is working on currently. The other, Hollow Core Fibre (HCF), is already deployed in some Azure regions and is being rolled out more broadly. 

Rather than guiding light through glass, HCF carries signals through a hollow air-filled core, enabling faster transmission and lower latency over equivalent distances. Published research indicates HCF delivers up to 47% faster data transmission and approximately 33% lower latency compared with conventional Single Mode Fibre. Developed at the University of Southampton and commercialised through Lumenisity, which Microsoft acquired in 2022, HCF is designed for longer-distance links between and beyond data centres.

Complementary technologies, shared infrastructure goals

Frank Rey, Partner and General Manager of Azure Hyperscale Networking at Microsoft, outlines how the two technologies operate in concert across different parts of the infrastructure.

"With MicroLED, you have the pure efficiency of LED over a laser," he says. "That has a pure bottom-line impact to power usage at any given data centre. 

“And then Hollow Core allows us to extend that area served by one data centre and an Azure region. And outside of an Azure region, if you can go a much greater distance before you need to do any signal amplification, that means less buildings, less power, less generators, less energy."