Relativity Networks raises $22 million to bring a faster kind of fiber to data centers

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Relativity Networks has raised $22 million in SAFE note funding from Rhapsody Venture Partners, Bell Ventures, and Faster Than Glass, alongside a $40 million follow-on order from a major unnamed hyperscaler. The company sells hollow-core fiber, which transmits light through a vacuum rather than glass, reducing signal travel time from roughly 5 microseconds per kilometer to about 3.5 microseconds—a 30% speed improvement. While that sounds incremental, the math becomes significant at scale: data centers now sprawl across hundreds of acres and multiple buildings, and multi-campus deployments are common as AI compute grows. A 30% latency reduction effectively allows campuses to be 30% further apart while still operating as synchronized compute units. CEO Jason Eisenholz frames this as the 'third era' of AI infrastructure: after GPU scaling and intra-datacenter networking, companies now need to optimize the geography of where compute sits. When AI compute occurred across a single rack, fiber latency was easy to ignore—but as GPU clusters span multiple campuses, microseconds matter for synchronization. The technology doesn't replace conventional fiber but fills a niche where tight synchronization across physical distance is essential.