Data center builders are racing to keep up with the explosive growth of cloud and AI computing, with trillions of dollars expected to be poured into new facilities worldwide. Yet even as developers battle for land, power, and political approval, one constraint has largely been treated as fixed: the speed of light through fiber.

Relativity Networks is challenging that assumption. The startup has raised $22 million in SAFE note funding from investors including Rhapsody Venture Partners, Bell Ventures Inc., and Faster Than Glass LLC, alongside a $40 million follow-on order from a major hyperscale customer that asked not to be identified. The capital will help Relativity scale a technology that could redraw the map of where and how data centers are built.

The company specializes in hollow-core fiber, a niche but long-sought alternative to conventional fiber-optic cables. Instead of guiding light through solid glass, hollow-core fiber channels it through an air or vacuum-filled center. Because light travels faster in air than in glass, signals can move up to 30 percent faster than in standard fiber.

Relativity CEO Jason Eisenholz estimates that a signal typically needs about five microseconds to travel a kilometer through conventional fiber. Hollow-core fiber can cut that to roughly three and a half microseconds. The difference is measured in microseconds, but at hyperscale, those microseconds compound into a meaningful competitive edge.

That edge matters more as AI workloads outgrow single racks and even single buildings. Modern AI clusters can span dozens of structures across vast campuses, and the largest operators are now stitching together multiple campuses into unified systems. As distances grow, latency between GPUs becomes a critical bottleneck.

Eisenholz argues that faster fiber can loosen the geographic constraints that have forced data centers into ever-tighter clusters near scarce power and network hubs. If latency budgets stay constant but signal speed improves by 30 percent, operators can spread facilities 30 percent farther apart while maintaining performance. That could open up cheaper land, tap underused power grids, and make it easier to expand existing sites into multi-campus complexes.

In his view, the industry is entering a new phase. The first wave of AI infrastructure focused on raw compute, the second on networking inside the data center. The next, he contends, will be about optimizing geography itself — and hollow-core fiber is designed to make that possible.