Lumilens, a two-year-old startup building optical-interconnection technology for data centers, has raised more than $700 million at a $5.5 billion valuation. The financing was co-led by Atreides Management, Bain Capital Ventures, Meritech, Seligman Ventures and Spark Capital. The San Jose, Calif.-based company has raised more than $900 million since its founding and recently began shipping equipment into the data centers of a large hyperscale cloud provider it declined to name.

As companies cram more-powerful graphics chips into data centers, moving information quickly between those processors is becoming a bigger challenge. Lumilens is among a group of heavily funded startups trying to solve that problem with light—using optical connections instead of electrical signals over wires. Graphics processing units today are typically connected with copper wiring, which is cheap and reliable but becomes less effective with larger data volumes over longer distances.

Competitors include Lightmatter, which has raised $850 million and was valued at $4.4 billion in 2024, and Celestial AI, acquired by Marvell in February for $3.25 billion. The prevailing challenge is cost: optical equipment can be several times more expensive than copper, according to Lumilens Chief Executive Ankur Singla, making it difficult to justify unless performance gains are significant.