Optical interconnect company Celestial AI has closed a $250 million Series C1 funding round, bringing the total raised to $515m.

The round was led by Fidelity Management & Research Company and saw participation from existing investors AMD Ventures and Koch Disruptive Technologies, and new investors BlackRock, Maverick Silicon, and Tiger Global Management.

Founded in 2020, the Santa Clara, California-based Celestial AI is developing an optical interconnect technology platform for data center and AI computing solutions. In October 2024, the company acquired the silicon photonics IP from Rockley Photonics, including the company’s worldwide issued and pending patents, for $20 million.

The company says its Photonic Fabric technology platform allows AI compute to be easily networked from within processor packages to servers across multiple racks, while its suite of products, which includes connectivity, switching, and packaging solutions, support optical scale-up networks for accelerated computing.

“With the emergence of complex reasoning models and agentic AI, the requirements on AI infrastructure are compounding,” said David Lazovsky, CEO of Celestial AI. “Cluster sizes must scale from a few AI processors in a server to tens of processors in a single rack and thousands of processors across multiple racks, all while relying on high-bandwidth, low-latency network connectivity to handle massive data transfers between processors.”

Lazovsky added: “Celestial AI’s Photonic Fabric is the only technology platform capable of meeting these critical demands while setting new standards for bandwidth, latency, energy efficiency, and total cost of ownership. We are excited to work with top global investors who bring the capital and commitment to support our long-term mission of revolutionizing AI infrastructure with our Photonic Fabric.”