Startups Challenge Copper's Reign in AI Data Centers with Radio Wave Technology

Radio and Terahertz Links Emerge as Potential Successors to Copper for AI Scale-Up December 27, 2025 The explosive growth of artificial intelligence is pushing the physical infrastructure of data centers to its limits. A critical bottleneck has emerged in the high-speed connections between the thousands of graphics processing units (GPUs) that power AI model training. While optical fiber handles longer-distance "scale-out" networking, the ultra-dense, short-reach "scale-up" connections inside server racks have long been the domain of copper cables. However, the industry is now hitting what some executives call the "copper cliff," where the physics of electrical signals at multi-terabit speeds demand thicker wires and more power, conflicting with the need for denser, more efficient systems. Two startups, Point2 Technology and AttoTude, are proposing a radical alternative: using radio waves within cables. Point2 is preparing to manufacture chips for a 1.6-terabit-per-second active radio cable (ARC) this year. The system uses eight polymer waveguides, each carrying 448 gigabits per second using millimeter-wave radio frequencies (90 GHz and 225 GHz). David Kuo, Point2's vice president, claims their solution consumes one-third the power and costs one-third as much as optical alternatives, while offering vastly lower latency. AttoTude is pursuing a similar path but in the terahertz frequency range (300-3,000 GHz), with founder and CEO Dave Welch highlighting electronics' inherent reliability over photonics. The fundamental issue with copper is the skin effect, which at high frequencies confines current to a thin outer layer of the wire, increasing resistance. To push data rates toward 1 terabit per second, copper cables must become shorter, wider, and more power-hungry. This poses a direct challenge to plans like Nvidia's aim to increase the maximum number of GPUs per system from 72 to 576 by 2027. While enhanced copper cables with retimer chips, known as active electrical cables (AECs), can extend reach—Credo has developed an 800 Gb/s AEC reaching 7 meters—many believe a more fundamental shift is needed. Both radio-wave startups argue their technologies offer a compelling middle ground. Point2's 1.6 Tb/s cable, at 8.1 millimeters in diameter, occupies half the volume of a comparable AEC and can reach 10-20 meters. AttoTude's terahertz waveguide, with fibers about 200 micrometers across, has demonstrated low signal loss and targets a 20-meter reach, which Welch calls "a beautiful distance for scale-up in data centers." Beyond pluggable cables, both companies see the ultimate prize in integrating radio transceivers directly with GPU packages, a feat they argue is simpler than with optics due to the longer wavelengths of radio signals easing precision manufacturing requirements. The industry, however, has deep inertia with copper. Don Barnetson, senior vice president at Credo, summarizes the prevailing mindset: "You start with passive copper, and you do everything you can to run in passive copper as long as you can." The move to liquid cooling for GPUs is itself an effort to preserve copper's viability at high densities. Yet, if successful, radio-based interconnects could not only postpone the copper cliff but also reduce cooling demands by allowing a more spread-out GPU arrangement. As AI models grow ever larger, the race to rewire the data center's heart is intensifying, with radio waves emerging as a surprising contender. Source: spectrum