Even as global financial markets wobble on Middle East-driven geopolitical risks, a very different trend is playing out in Korea's stock market. Over the past month, it wasn't semiconductors but optical communication stocks that dominated the top tier of market returns. After Nvidia CEO Jensen Huang cited optical technology and silicon photonics as core pillars of next-generation AI infrastructure at "GTC 2026" on the 17th of last month, speculative money and growth expectations surged into related names all at once.
According to the industry on the 17th, shares of optical communication company INNO INSTRUMENT jumped 746.8%, from 359 won on the 17th of last month to 3,040 won on the 16th of this month. Based on the intraday high of 5,080 won the previous day, they were up 1,315.3%. During the same period, AUK, an optical communication-related company, rose 520.2% from 2,080 won to 12,900 won; Wooriro climbed 768.5% from 1,635 won to 14,200 won; Gigalane advanced 292.2% from 510 won to 2,000 won; Lightron Fiber-Optic Devices gained 192.7% from 1,541 won to 4,510 won; and Taihan Fiberoptics increased 108% from 7,220 won to 15,020 won. All of them posted not only double-digit but triple-digit gains in less than a month.
Behind this sharp rally is a shift in AI infrastructure architecture. As demand for graphics processing units (GPUs) connected inside data centers has surged with the spread of Generative AI, it has become as important as semiconductor performance to move data quickly and efficiently. Nvidia also emphasizes that silicon photonics can enable ultra-large AI infrastructure to run faster and more energy efficiently. The market sees the center of gravity in AI competition broadening from the chip itself to the networks and optical interconnects that link chips.
What the market especially focused on was not simple "optical fiber," but a change in the internal connection architecture of AI data centers. Previously, electrical-signal-based connections dominated when linking servers to switches and chip to chip, but as GPU density rises, limits are emerging in the form of increased heat, power consumption and latency. As a result, optical technologies that transmit data with light are emerging as next-generation solutions. The industry expects technologies such as optical transceivers, optical cables, silicon photonics and co-packaged optics (CPO) to directly benefit from expanding AI infrastructure investment. In Korea's stock market, these expectations are spreading quickly, triggering a wave of re-evaluation that lumps together related component, equipment and module makers.
However, signs of heightened volatility after the surge are also clear. On the 16th alone, INNO INSTRUMENT fell 29.95% from the previous day; AUK dropped 27.45%; Gigalane declined 29.95%; Lightron Fiber-Optic Devices slid 29.42%; and Taihan Fiberoptics plunged 24.14%. Because expectations lifted share prices first, volatility could increase further unless earnings or actual orders follow through.
In the end, market attention is likely to shift from the label "optical communication" itself to corporations with real competitiveness. Observers say practical relevance to AI data centers, core optical component and equipment capabilities, and entry into global big tech supply chains will become the criteria for separating the wheat from the chaff. While this rally could be an opening shot for an infrastructure reshuffle in the AI era beyond a simple theme-driven market, the current phase is closer to an early stage where expectations and overheating are mixed.
Kim Kyung-won, a distinguished professor in the Department of Business Administration at Sejong University, said, "The broad trend of optical communication emerging as a core pillar of AI infrastructure is correct, but not all related stocks will benefit equally," adding, "The difference between corporations that tie into actual customers, supply chains, mass-production capability and revenue, and corporations that merely ride the theme is likely to become clear soon."