Data center developers are expected to spend up to $4 trillion by the end of the decade, but buildouts remain constrained by politics and power-grid limitations. Relativity Networks announced $22 million in SAFE note funding from Rhapsody Venture Partners, Bell Ventures Inc., and Faster Than Glass LLC, among others. A SAFE note converts into shares at the next priced round, a standard instrument for early-stage startups. The company also secured a $40 million follow-on order from an unnamed leading hyperscaler.

Relativity Networks works with hollow-core fiber, a technology that transmits light through a vacuum-filled core rather than traditional glass. This brings signals closer to the speed of light, cutting latency by 30%. CEO Jason Eisenholz notes that a signal travels one kilometer in about five microseconds through conventional fiber; hollow-core reduces that to three and a half microseconds. While the per-meter difference is tiny, it becomes significant in large data center campuses spanning hundreds of acres, where GPUs are now distributed across many buildings.

Eisenholz sees particular opportunity in multi-campus deployments, where existing data centers are linked to operate as one synchronized machine, especially where power limits expansion in a single location. This approach effectively extends the distance over which latency stays within tolerance by 30%, giving developers more geographic flexibility. He describes this as a third era of AI optimization: after optimizing compute and then intra-data-center networking, the industry is now optimizing geography.