Microsoft and EPFL Push Forward Optical Circuit Switching for Data Centers

Recent years have brought tremendous growth in data center traffic due to booming applications, including machine learning and cloud computing. 

At the same time, the slowing of Moore's law has left data center architects in a challenging position, trying to design power-efficient electrical switches that keep up with the growth while not relying on traditional scaling. 

 

A photonic integrated platform for the data center. Image used courtesy of Aqeel Ahmed and EPFL

 

The limits for electronic switching are starting to be reached, and one alternative that has been actively looked into is optical switches; however, this comes with challenges of its own. 

This week, researchers from EPFL (École Polytechnique Fédérale de Lausanne) and Microsoft have announced a new optical switching technique involving microcombs, which they believe can pave a path towards a more scalable and energy-efficient data center. 

 

Switching in the Data Center

In today's data centers, the high distance-bandwidth product (the combination of physical scale and bandwidth) has required the use of fiber optics. While interconnects are optical, switching is currently still performed electronically. 

This scheme is far from ideal, as it requires converting the signal from electrical to optical, which is both power consuming and time-consuming. 

On the other hand, optical switching is an appealing solution since it allows for high bandwidth, low network latency, and improved power efficiency since we remove the need for signal conversion. 

 

The principle behind electrical switching. Conversion between optical and electrical signals represents a power and latency bottleneck in data centers. Image used courtesy of Fracasso et al

 

A specific form of optical switching that has garnered much interest is wavelength switching, where individual servers are connected using multiple wavelengths of light. In this technique, a dedicated switching element modulates the wavelength of light and routes the signals to their destination servers. 

Unfortunately, wavelength switching technologies are very slow, making them unable to handle high-speed "bursty" data center applications while properly using network resources. 

 

Microsoft and EPFL's Switching Solution 

These challenges are exactly what the researchers at Microsoft and EPFL have sought to overcome, speeding up wavelength optical switching to make the technology feasible for the data center. 

In their paper, the researchers propose a new technique for wavelength switching, which they claim is capable of switching on sub-nanosecond time scales.

 

The schematic setup, which is used for the optical circuit switching. Image [modified] used courtesy of Raja et al

 

The new technique leverages photonic chip-based soliton microcombs, a photonic device capable of generating optical frequencies on a microresonator, as a multi-wavelength source. 

The researchers explain their scheme, where a single wavelength establishes a link between two servers in specific time slots, and a central soliton microcomb generates these wavelengths. 

The physical switching is then achieved by control circuitry that applies control signals to an array of silicon optical amplifiers (i.e., turning the amplifiers of the desired path on while turning the others off). 

By using microcombs as a wavelength source, the researchers achieved ultra-fast (sub-nanosecond) switching carriers at low power relative to electrical switching counterparts.

 

Paving the Road to the Future

With the increased strain on today's data centers, many have looked to optical circuit switching to increase speeds and decrease power consumption. Historically, wavelength-based optical switching has proven too slow to maintain the speeds required by modern data center applications. 

In this study, however, the researchers were able to demonstrate a new architecture that has the ability to realize the packet-by-packet switching rates required to fulfill the requirements of data center applications. 

While this work may be a long time from reaching the industry, it is important nonetheless, as it could pave the way for more performant, power-efficient data centers in the future.

 

---

 

Interested in more data center news? Read on in the articles down below.

Micron Seeks to Solve Data Center Challenges with New Generation SSD

Semtech Strives for Data Center Interconnects with Latest Tri-Edge Chipsets

AI Accelerator Chip with 1000 RISC-V Cores Shakes Up Data Center Inference