Corning shares slide as fiber boom faces investor scrutiny

Corning shares have fallen about 50% from their June peak despite surging demand for optical fiber used in AI data centers. Investors are questioning stretched valuations, the durability of technology companies’ infrastructure spending and potential dilution after Corning signed an agreement allowing it to issue up to $2 billion in new shares. Its October 27 earnings report will test whether business momentum remains intact.

Fiber accounted for 45% of sales in the first half of 2026. Optical communications sales reached $2.07 billion in the April-June quarter, up 32%, while enterprise networking, including hyperscale data centers, grew 65%. Corning has secured partnerships with Nvidia and Amazon, alongside a $3 billion contract with AT&T to upgrade home internet service. Chief Executive Officer Wendell Weeks is targeting $40 billion in revenue by 2030.

The expansion carries echoes of the telecom bubble, whose collapse in 2001 devastated fiber demand and sent Corning’s stock plunging from $113 to $1.10. To reduce dependence on communications spending, the company is developing automotive uses for Gorilla Glass and expanding integrated solar manufacturing. Solar-related sales reached $808 million in the first half of 2026, nearly doubling from a year earlier. Diversification offers another growth avenue, but optical communications remains exposed to spending decisions by a handful of large technology customers.