AI’s bottleneck moved from chips to wiring. This startup raised $700m to fix it with light

Lumilens came out of stealth on Thursday with a big number and a bigger claim. It announced more than $700m in fresh funding, taking its total to over $900m and valuing it at $5.51bn. It also says it is already shipping its first product into a hyperscaler’s live data centres, under a deal it says is worth billions.

The pitch rests on a shift the whole industry is feeling. “The constraint on AI has shifted from how many GPUs you can buy to how many you can connect,” said founder and chief executive Ankur Singla. Modern models run across hundreds of thousands of chips that have to behave as one computer. The wiring between them now matters as much as the chips.

Copper hit a wall

Two problems bite. Across racks, every GPU you add multiplies the optical transceivers needed. A single 400,000-GPU site needs more than 2.4 million of them, and the market cannot keep up. Inside the rack, GPUs are wired to each other over copper, and copper is out of road.

At AI speeds an electrical signal survives about a metre and a half over copper. That caps a tightly linked cluster at a few hundred chips. To wire thousands together, you have to swap copper for light. That is Lumilens’s business: optical interconnects for both jobs, the short hops inside a rack and the long ones between them. It is the same copper bottleneck that pushed Nvidia into photonics.

A crowded, hyped race

Investors are treating it as a landmark. The round was co-led by Atreides Management, Bain Capital Ventures, Meritech, Seligman Ventures and Spark Capital, with Qualcomm Ventures and JPMorgan among the rest. Mayfield’s Navin Chaddha, who has backed Singla three times, said he had never seen growth like it in the firm’s 56-year history.

There is substance behind the froth. Singla has built and sold two infrastructure companies before, Contrail to Juniper and Volterra to F5. His team comes from Cisco, Meta and Marvell. The spending backdrop is real too. Citigroup expects AI infrastructure outlays to pass $2.8tn by 2029.

The caveats are worth stating.

The marquee customer is unnamed, and the multi-billion-dollar deal is Lumilens’s own figure, not an audited one. It is also not alone. Co-packaged optics is one of the hottest corners of the chip world, contested by Nvidia, Broadcom and a row of startups.

A fat private valuation is easier to win than a durable lead. Its Chinese rivals, from Eoptolink down, are chasing the same prize. For now, Lumilens has the thing the market values most: a product already inside a data centre. Moving data has become harder than crunching it.