Zhongji Innolight Surpasses CATL as China's Largest CSI 300 Stock at 5.3% Weighting — AI Optical Hardware Boom Reshapes China's Benchmark Equity Index

Zhongji Innolight Co. (SHE:300308), a Chinese manufacturer of high-speed fiber optic transceiver modules for AI data center interconnects, became the largest constituent of China's CSI 300 Index with a 5.3% weighting, overtaking EV battery giant CATL at 4.1%, the South China Morning Post reported on June 5. Zhongji Innolight shares had achieved a fivefold increase during 2025 and nearly doubled again in 2026 — Q1 2026 net profit grew 262% year-on-year; full-year 2025 net profit rose 108% YoY. The company's explosive growth reflects the AI hyperscaler infrastructure buildout: high-speed optical transceivers are essential for connecting server racks within AI training and inference data centers, and demand is surging as both US and Chinese hyperscalers race to expand GPU cluster capacity. Major customers: Alphabet/Google (22% of sales), Amazon (11%), Meta (6.4%), Huawei (5%), Alibaba (1.9%). The customer list is uniquely trans-Pacific — Zhongji Innolight simultaneously supplies the US hyperscalers driving the Western AI buildout AND Chinese domestic AI cloud infrastructure, making its optical components one of the few technology products explicitly exempt from the US-China chip export control perimeter. The CSI 300 weighting shift from CATL to Zhongji Innolight is read as a structural inflection signal: China's equity markets are repricing from 'EV era benchmark stock' (CATL, dominant 2020–2024) to 'AI era benchmark stock' (Zhongji Innolight, 2025–2026) — the composition of China's blue-chip index now reflects the AI infrastructure investment cycle rather than the EV transition cycle. Bloomberg's June 4 report confirmed the development. The Zhongji Innolight ascendancy also illustrates how China's supply chain position in AI hardware extends beyond chips — the US-China tech bifurcation is chip-centric, but optical networking, power management, and packaging supply chains are globally integrated and flowing toward China.