光学PCIe拓展AI机架设计的连接距离

Close-up of data center equipment

Optical PCIe is being explored to give operators greater freedom to separate GPUs, switches, and memory across racks as AI systems grow denser.Getty Images

As AI racks become denser and PCIe data rates continue to rise, traditional electrical interconnects face familiar constraints in reach, signal integrity, power, thermal management, and cable density.

Optical PCIe is emerging as one possible way to ease some of those pressures. PCIe, or Peripheral Component Interconnect Express, is a widely used architecture that links accelerators, switches, memory, storage, and other devices. Optical PCIe preserves that architecture but carries the signals as light over fiber rather than as electrical signals over copper.

At the 2026 OCP Global Summit in San Jose, Lumentum, Astera Labs, and Corning used a rack-level demonstration to show how that approach could work in practice. The setup combined Astera Labs’ Scorpio Smart Fabric Switch, Lumentum’s optical interconnect, and Corning multimode fiber. The links used VCSELs (vertical-cavity surface-emitting lasers), which are semiconductor lasers that emit light from the chip surface. Lumentum described the system as a proof of concept, not a product announcement.

“Optical PCIe does not eliminate every system constraint, but it can relax several of them by moving data over lightweight, low-loss optical links across longer distances,” Christian Urricariet, senior director of product and strategic marketing at Lumentum, told Data Center Knowledge.

Copper’s Limits Become More Apparent as AI Systems Scale

One of the clearest pressure points for electrical interconnects is distance.

“Given today’s high data rates as well as future even higher data rates, optical connections can span tens to hundreds of meters within a data center,” Joshua Fennimore, commercial technology manager at Corning Optical Communications, told Data Center Knowledge. “Passive copper connections are generally limited to only a few meters, while active copper can extend somewhat farther.”

Those constraints become harder to manage as PCIe speeds increase. Urricariet said that higher PCIe data rates make electrical links more sensitive to loss, crosstalk, and equalization requirements over the distances that operators want to support.

“Designers may need to add retimers or place connected devices closer together, while high-speed copper cables can become bulky and difficult to route and manage,” Urricariet noted.

More Reach Could Reshape Rack and Row Design

The practical appeal of optical PCIe is not simply replacing copper with fiber. It is the ability to change where infrastructure can be placed within a rack, or even across multiple racks.

Fennimore said copper’s limited reach tends to keep switches and compute hardware physically close together. Fiber, by contrast, gives designers more room to separate those systems while still maintaining high-speed connectivity.

“Fiber allows those systems to be separated across racks or rows inside a data center, giving operators greater flexibility to optimize rack layouts around compute density, power, cooling, serviceability, and cable management,” Fennimore said.

That added reach could support broader architectural changes as well. Jignesh Shah, senior director of product marketing for the Signal Connectivity Group at Astera Labs, said optical PCIe could enable scale-up designs that span multiple racks rather than being confined to a single enclosure or a short electrical path.

“With optical PCIe, reach can be tens of meters, which allows for large scale-up architectures across multiple racks and disaggregated scale-up architectures, with dedicated racks for GPUs, switches, and memory,” Shah told Data Center Knowledge. “Optical PCIe also enables high-density solutions, which are needed for high-radix switches and GPU applications.”

In practical terms, the promise of optical PCIe is greater flexibility for system architects. By easing the constraints imposed by the electrical channel budget, Urricariet said, optical PCIe could make it easier to build more modular and composable rack-scale designs, particularly in AI environments where power delivery, thermal limits, and serviceability are becoming just as important as raw performance.

Copper Still Has a Strong Role

Even as vendors push optical PCIe forward, copper is not going away.

For short distances, copper remains the more established and cost-effective choice. According to Shah, once designs move beyond about 3 meters of reach, operators are at a point where it makes sense to evaluate both copper and optical options.

“Ultimately, the variables that customers care about come down to power, density, and latency requirements, which can influence a decision between copper and optical,” Shah said. “Optical can support higher density and lower latency, but given copper’s maturity, copper currently offers the best TCO for anything within a few meters.”

A Working Demo, Not Yet a Broad Deployment Story

For now, the technology remains in its early stages.

Urricariet said the OCP demonstration showed fully operational optical links using multiple 32 GB/s channels and an error-free PCIe 5 link in a rack-representative system. But moving from a controlled demonstration to broad deployment will require more than a successful show-floor proof of concept.

“Moving from a demonstration to broad deployment requires further work across system integration, reliability, manufacturing, and customer qualification,” Urricariet said.

Copper still has a place, and that’s not going to change, but as the demands of AI data centers grow, optical PCIe provides another option.

“The goal is not to suggest that every PCIe connection will become optical, but to expand the set of practical system architectures as AI racks grow in scale and complexity,” Urricariet said.

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Sean Michael Kerner is an IT consultant, technology enthusiast and tinkerer. He consults to industry and media organizations on technology issues.

https://www.linkedin.com/in/seanmkerner/