Fujikura: The 140-Year-Old Japanese Cable Maker Wiring AI Data Centers With Light

We covered what is physically inside a data center in Inside a data center (in Japanese). Within it, vast quantities of optical fiber connect server to server and rack to rack. Why glass fiber can carry data at all is explained in How optical fiber works (in Japanese). Fujikura is the company that both makes that fiber and joins it together.

What kind of company is Fujikura?

Fujikura is a Japanese maker of optical fiber, optical connectors, electrical wire, and automotive components. One of Japan's Big Three cable makers alongside Sumitomo Electric and Furukawa Electric, it holds particular global strength in joining optical fibers together. It is listed on the Tokyo Stock Exchange Prime Market (ticker 5803).

The company was founded in 1885, when Zenpachi Fujikura began manufacturing insulated winding wire in Kanda, Tokyo. Fujikura Electric Wire Co. was incorporated in 1910 and grew as a maker of power and telecom cables. It began mass-producing optical fiber in the 1980s, gradually shifting its center of gravity from copper wire to optical communications components (Fujikura Ltd.).

For the fiscal year ended March 2025 (FY2025), consolidated revenue was 979.4 billion yen, operating profit 135.5 billion yen, and net profit attributable to shareholders 91.1 billion yen — all record highs. What defines today's Fujikura is that these records were driven not by its long-standing wire business but by the telecom segment built around optical fiber (Fujikura Ltd.).

How is Fujikura's revenue composed?

Fujikura operates five segments: telecom ("Information & Telecommunication"), covering optical fiber and optical wiring; electronics, centered on FPCs (flexible printed circuits — bendable circuit boards); automotive, centered on wire harnesses (the bundled wiring inside vehicles); energy, covering power cables; and real estate.

The FY2025 breakdown of the 979.4 billion yen in consolidated revenue is as follows (the telecom figure is as disclosed in earnings; others are estimates from the disclosed mix).

(Source: Biz/Zine)

The standout is the telecom segment's growth. In FY2025 it posted revenue of 451.3 billion yen (up about 51.8% year on year) and operating profit of 92.2 billion yen (up about 135.2%), a single segment earning the majority of the group's 135.5 billion yen in operating profit. Data center optical cabling demand is the main driver of this surge (Biz/Zine).

The long-loss-making automotive segment also recovered to an operating profit of 5.8 billion yen in FY2025 through restructuring and cost pass-through. Even so, Fujikura's earnings engine is now unmistakably telecom — that is, light.

Where do Fujikura's technical strengths lie?

Fujikura's technical strength is that it controls not only the making of optical fiber but the joining of it, end to end. Optical fiber carries signals by total internal reflection of light within glass, and the quality of a link depends on joining fibers with minimal loss. Fujikura leads the world in that joining step.

The first pillar is the optical fiber fusion splicer. Fusion splicing melts the end faces of two fibers together with an electric arc, fusing them into one — a method prized for low loss and high reliability. Fujikura's fusion splicers are world number one, with a global share said to exceed 50%, making them the de facto standard machine on telecom and data center construction sites (Nikkei Business).

The second pillar is multi-fiber connectors and ultra-high-density cables. A multi-fiber connector lets many optical fibers be plugged and unplugged in a single action, and Fujikura holds the world's top share in the ferrule — the precision part at its heart that holds fibers in exact alignment. Its SWR/WTC ultra-high-density cables pack up to 6,912 optical fibers into a single slim cable, threading enormous line counts through a data center's limited space (Fujikura Ltd.).

Combining these into an "optical wiring solution" is the core of Fujikura's differentiation. With fiber, connectors, fusion splicers, and installation engineering all from one company, data center operators can build high-density optical cabling quickly and reliably. The next step — connecting chips themselves with light — is covered in Silicon photonics and co-packaged optics (in Japanese).

What role does Fujikura play in the supply chain?

Fujikura's role in the supply chain is as the supplier of the infrastructure components that connect light. Inside data centers, between data centers, and across the ocean floor between continents — wherever light travels, Fujikura's fiber and interconnect components are in use.

Concretely, it operates at three layers. First, inside the data center, connecting servers and switches with multi-fiber connectors and slim high-density cables. Second, between data centers, supplying long-haul optical cables that span sites. Its main customers are the giant cloud operators known as hyperscalers.

The third layer is submarine cables. Fujikura supplies the optical fiber and related components used in undersea systems. The manufacturing and laying of submarine cables themselves is led by players such as NEC-affiliated OCC and Sumitomo Electric, but the fiber running through them comes from specialist makers like Fujikura. The full picture of that industry is covered in Who builds and owns the world's submarine cables, and where those cables reach Japan in Japan's cable landing stations.

The spread of AI is lifting demand across all three layers. Generative AI training and inference generate enormous traffic inside and between data centers, accelerating the shift to thinner, denser, higher-count fiber. The result is a need for more fiber and faster connection technology — a tailwind blowing straight into Fujikura's optical wiring solutions (Nikkei).

What do Fujikura's market position and competitive structure look like?

Fujikura stands at the global top tier across multiple optical interconnect categories: world number one in fusion splicers, world-leading share in multi-fiber connector ferrules, and a head start in ultra-high-density cables — differentiating through integrated strength in connecting light.

A five-forces view of the optical fiber and cabling market looks like this:

(Source: Fujikura Ltd.)

Optical fiber itself is an oligopoly shared with Sumitomo Electric, Furukawa Electric, and Corning, but in the joining of fiber — fusion splicers and connectors — Fujikura's presence stands apart. The common entry barrier is integrated mass-production capability from preform to connection, plus incumbency as the field standard: once designed in, it is hard to displace.

What are Fujikura's weaknesses and risks?

The biggest risk is its growing dependence on telecom and AI demand. In FY2025, the telecom segment earned the majority of group profit — meaning that if AI data center investment stalls, the company's largest profit source takes the direct hit. Being a cyclical, market-linked business with large demand swings is a structural weakness.

The second is raw material and market volatility. Wire and cable profitability moves with copper, silica glass, and resin prices. The energy and automotive segments skew commodity-like, and margins thin quickly when price pass-through lags. The strength of telecom is partly masking the cyclicality of these other businesses.

Added to this, competitors are all expanding at once. Sumitomo Electric, Furukawa Electric, and Corning are each adding data-center fiber capacity, and once AI demand digests, oversupply and price declines could follow. Fujikura's value rests on differentiation in connection technology and density — staying out of the commodity fiber price war is the design challenge.

What has Fujikura been doing lately?

Recent Fujikura is accelerating capacity investment to capture the AI data center boom. In May 2026 it announced up to 260 billion yen of investment in the United States to expand data-center optical fiber cable production, which together with 40 billion yen of domestic investment brings the program to as much as 300 billion yen. The expansion of AI infrastructure has pushed optical wiring to the center of the company (Nikkei).

On the product side it is keeping pace with soaring fiber counts. In April 2026, Fujikura launched the 100R, a new multi-fiber fusion splicer handling everything from single fibers up to 16-fiber intermittently-bonded ribbon (multi-fiber ribbon bundled into thin tape). Domestically, it is investing about 45 billion yen in a next-generation optical fiber plant in Chiba Prefecture, slated to start operating in fiscal 2029 (OPTRONICS ONLINE / Nikkei).

After 140 years as a "wire company," Fujikura is swapping its lead role from copper to light and reshaping itself into a company that underpins the communications infrastructure of the AI era. It makes no flashy end products and no chips — but the more data AI generates, the more quietly indispensable Fujikura's role in connecting the light that carries it becomes.

Key takeaways

• Fujikura, founded in 1885, is one of Japan's Big Three cable makers, with strengths in optical interconnect products: fiber, connectors, and fusion splicers.
• FY2025 (ended March 2025) consolidated revenue was a record 979.4 billion yen with operating profit of 135.5 billion yen; the telecom segment accounts for about 46% of revenue and the majority of operating profit.
• Its strengths combine the world's top-share fusion splicer, the world-leading multi-fiber connector ferrule, and SWR/WTC ultra-high-density cables into an optical wiring solution for AI data centers.
• AI data center growth is driving a buildout including up to 260 billion yen of US investment and a 45 billion yen new plant in Chiba.
• Risks are dependence on telecom and AI demand, market cyclicality, competition with Sumitomo Electric, Furukawa Electric, and Corning, and swings in copper and silica glass prices.