Verizon's Corning fiber deal sent Korean optical stocks soaring, even with no Korean supplier named

Korean optical communication stocks rose sharply in Seoul on Wednesday after Verizon and Corning announced a large US fiber supply contract. Mercury (머큐리) closed at its daily limit of 30 percent, and the Kosdaq finished the session up 2.28 percent at 830.37.

Verizon and Corning said on September 8 that Corning will supply more than 80 million miles of high-density optical fiber and connectivity products between 2027 and 2032. The fiber is meant for home and business broadband, and for the long-distance network that carries AI traffic between data centers. The announcement names no Korean supplier.

Seoul bought the idea anyway. Mercury closed at 4,355 won ($3.25), up 30.00 percent, after opening the day unchanged. Wooriro (우리로) also finished at the limit, up 29.84 percent to 6,570 won ($4.90). RF Materials (RF머트리얼즈) rose 22.61 percent to 42,300 won ($31.54), Etoday (이투데이) reported. Lycom (라이콤) rose 14.10 percent and Woorinet (우리넷) rose 12.18 percent.

Taihan had disclosed orders but gained the least

Taihan Fiberoptics (대한광통신) rose 9.20 percent to 14,960 won ($11.16). That was the smallest gain of the six. It had already disclosed cable orders for AI data centers.

Taihan won its first order for 864-core optical cable in February and a second one in June. CBC News (씨비씨뉴스) put the two together at about 41.1 billion won ($30.6M) on August 3. The June order is being delivered from July of this year through the end of 2027.

Lee Seung-woong, an analyst at Yuanta Securities (유안타증권), wrote on September 2 that an 864-core cable carries about three times as many fiber cores as a 288-core cable. "In AI data centers, total demand for optical fiber is rising and cables are moving to higher core counts at the same time," Lee wrote. The note also said that "Taihan Fiberoptics has brought its raw material in house and has stable yields, which let it handle changes in the price of optical fiber," Newspim (뉴스핌) reported.

What Mercury actually sells

Mercury's main business sits further from that contract. It supplies home wired and wireless routers and optical modems to Korea's three telecom carriers. Its subsidiary Mercury Optical Communications (머큐리광통신) is the part that makes optical fiber cable, and that unit is what turned the parent around this year.

First-half revenue was 56.2 billion won ($41.9M), up 4.6 percent from a year earlier. Operating profit was about 2 billion won ($1.5M), against a loss of 2.5 billion won ($1.9M) a year earlier, Etoday reported on August 18. "The turn to an operating profit in the first half came from growth in the optical communication business together with company-wide work on profitability," a Mercury official said.

The two companies aren't the same size

Mercury's market value is about 74.6 billion won ($55.6M). Taihan's is about 2.3261 trillion won ($1.73B), which is about 31 times larger by our arithmetic.

Neither one made money per share over the past year, so there's no price-to-earnings ratio to quote for either.

Both are also well below where they traded earlier this year. Mercury is up 43.7 percent in 2026 by our arithmetic, and it's still 65.8 percent under the high it set on April 14. Taihan is up 601.7 percent this year by our arithmetic, and it's 52.5 percent under its own high from May 12.

Wednesday's buying was a Korean theme trade, where one piece of news moves a whole group of related stocks at once. Taihan's cable orders are separate contracts and have nothing to do with the Verizon agreement. In August, four Korean biotech stocks hit their daily limit on a trial result from Moderna. Korean suppliers do win real work from American AI projects, as Hyosung Heavy Industries has with power equipment.

Meanwhile, Corning's fiber under the Verizon deal isn't scheduled to start shipping until 2027.

Quotes from Korean-language sources are translated from Korean. Won figures are converted at 1,341 won to the dollar, the Naver Finance rate on September 9, 2026.