AI Infrastructure Stocks Plummet, Losing Over 7 Trillion Won in Market Value in One Day

On the 26th, Ciena Corp. (CIEN) shares closed at $391 on the New York Stock Exchange, plunging 10.71% from the previous day. In a single session, the company’s market capitalization evaporated by about $5.3 billion (roughly KRW 7 trillion), while trading volume surged to 2,094,873 shares.

In its fiscal 2025 third-quarter earnings report, Ciena announced it would halt certain broadband development investments—particularly in 25G PON—and institute a restructuring plan that reduces its global workforce by approximately 4–5%, reallocating resources toward high-growth areas. Earlier in fiscal 2025, the company signed an agreement to acquire Nuvis Communications, a provider of ultra-compact, low-power optical-electrical interconnects optimized for AI workloads, to accelerate its response to AI data-center network demand.

Headquartered in Hanover, Maryland, Ciena is an optical-transmission and networking-equipment company that supplies high-speed optical communication systems and network software to telecommunications carriers and cloud service providers worldwide. Founded in 1992, this mid-tier network vendor counts major operators such as AT&T and Verizon among its clients and has long been viewed as a prime beneficiary of expanded optical-transport infrastructure spending driven by rising AI and cloud traffic.