Meeting the Cabling Needs of Future Data Centers

With AI and machine learning increasing in adoption, the need for robust cabling to handle signals with higher bandwidth is becoming paramount. While copper cables have long been used for data centers, their bandwidth limitations are likely to surface as AI applications increase. Sean Park, co-founder and CEO of Point2 Technology, a startup company that has developed an interesting alternative to copper for high-speed cabling designated e-Tube.

In a recent e-mail interview with Design News, Park discusses the issue of high-speed cabling for data centers and touches on how e-Tube could potentially solve some of copper’s limitations.

DN: What are limits of existing copper interconnects for data centers?

Most of today’s data centers rely on 400 gigabit (400G) Ethernet network devices, which can be served with passive copper direct attached cables (DACs). However, AI and machine learning workloads are quickly driving speeds to 800G and eventually 1.6T. While known for being simple, reliable, and inexpensive, copper cables are not equipped to handle these speeds because they experience significant signal loss, which reduces cable length. While thicker copper wire gauges can extend the cable length, that causes the overall DAC to become too thick, heavy, and rigid to be deployed and serviced for in-rack use cases.

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DN: There has been a lot of talk on optical interconnects, but mass adoption does not appear to be rapid. What promises do optical interconnects hold for future hyperscale data systems, and what drawbacks remain with the technology?

The paradigm is to use copper when possible and optical when necessary. Since copper is reaching its physical limits in addressing increasing data center speeds, enterprises and hyperscalers will have to turn to optical interconnects, such as active optical cables (AOCs), for AI-related workloads. AOCs integrate advanced DSP and complicated optical assemblies to transmit and receive optical signals at high speeds. These cables are thinner, lighter, and support longer cable length than copper, making them easier to deploy and service.

However, end users avoid optical interconnects due to their high power consumption and cost from the DSP and optical assemblies. Compared to copper, optical interconnects are up to 7x more expensive and add significant power to data center operations. Even with innovations such as co-packaged optics, they still pose significant cost, heat, power, and reliability challenges for high-volume, in-rack, and adjacent rack applications.

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DN: What other cabling solutions are being looked at?

Active electrical cables (AECs) are another option for hyperscalers to consider. They contain a silicon system-on-chip (SoC) inside the cable assembly, which recovers high-speed signal loss over copper wiring to improve performance and reliability. Because of this, AECs are compatible with longer-reach applications, such as in-rack and adjacent-rack connections. Like optical cables, they are smaller and lighter than passive copper cables, reducing congestion in racks and the energy needed for cooling.

However, AECs can still consume significant power depending on the SoC. For example, a typical 800G AEC with a PAM4 DSP will consume about 20W, while a purpose-built mixed-signal interconnect SoC will consume only 11W. And once the speeds reach 1.6T, even AECs will have cable reach, power, and cost limitations for mass deployment.

DN: What does Point2 Technology’s e-Tube promise as far as overcoming the obstacles of other technologies? What are the disadvantages?

Recognizing the limitations of copper and optical interconnects, Point2 Technology developed e-Tube, a scalable interconnect platform using RF data transmission through a plastic dielectric waveguide made of common plastic material, such as Polyethylene. e-Tube offers lower loss, longer reach, and more power efficiency at a similar cost to copper interconnects. e-Tube cables are designed to meet MSA-defined standard form factors such as OSFP and QSFP-DD for deployment in existing infrastructure.

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e-Tube cables are 50% thinner than copper and don’t suffer the same high-frequency loss as data transmission speeds scale. Yet, e-Tube overcomes the power and cost challenges of optical interconnects, offering roughly 50% better energy efficiency than co-packaged optics and 75% better energy efficiency than traditional re-timed optics. With e-Tube, hyperscalers can sustainably and effectively scale their operations as speed demands reach 800G, 1.6T, and eventually 3.2T.