Corning Slides 20% on Q3 Miss, Coherent Falls on Read-Through Fears

Corning shares plunged more than 20% on July 28 after the optical-networking giant issued third-quarter sales guidance that fell short of elevated Wall Street expectations. The selloff dragged down shares of Coherent Corp., a key supplier of active optical components, as investors rapidly reassessed the trajectory of artificial-intelligence infrastructure spending.

The severe reaction overshadowed a fundamentally robust second-quarter performance. Corning posted core sales of $4.74 billion, up 17% year over year, alongside core earnings of $0.78 per share, a 30% increase. Optical Communications revenue jumped 32% to $2.07 billion, powered by a 65% surge in Enterprise Networks and significantly faster growth in generative-AI product sales.

However, Corning's projection of $4.9 billion to $5.0 billion in third-quarter core sales failed to satisfy a market priced for uninterrupted acceleration. The guidance implies roughly 16% annual growth but came in slightly below analyst consensus. The pace of optical growth also decelerated from 36% in the first quarter to 32% in the second. After gaining roughly 64% in 2026 through the prior close, the valuation left no margin for even a modest slowdown.

The immediate spillover to Coherent reflects the interconnected nature of AI data-center architecture. Corning supplies the passive physical layer of these networks, including optical fiber, cabling, and dense connector systems. Coherent manufactures the active endpoints, producing lasers, photodiodes, and the 800G and 1.6T transceivers required to convert electrical signals into light.

Because expanding AI clusters demand both increased fiber paths and faster optical endpoints, Corning's order pace provides a partial read-through on deployment volumes for Coherent. Crucially, Corning's metrics cannot establish Coherent's market share, product pricing, or manufacturing yields. Coherent's latest quarter, ended March 31, underscores this divergence, reporting a 21% revenue increase to $1.81 billion and a 37.7% GAAP gross margin alongside exceptionally strong data-center demand for its 1.6T transceiver roadmap.

Market mechanics offer no alternative explanation for the magnitude of Corning's decline. Short interest stood at 19,125,152 shares on July 15, equal to just 2.23% of the public float, eliminating a short squeeze as a catalyst. While hedge fund long positions had grown to 91 portfolios at the end of March, up from 85 in December, those stakes preceded the guidance disappointment.