STL is the only Indian maker of silica glass preforms, the hardest part of optical fiber. Its ₹1,200 crore bet expanded capacity from 30 million to 50 million fiber kilometers, capturing 40–45% of India's market.
Founded in 1988 as a copper cable maker, STL entered optical fiber in 1993 and demerged in 2000. Today it runs ten facilities across four continents, serving over 100 countries with 3,800-plus employees.
Demand for low-latency optical connectivity is at an inflection point from 5G, fiber-to-the-home rollouts, and AI data center buildouts. AI racks are scaling from about 500 fibers to over 16,000 fibers per switch rack.
Between 2018 and 2019, STL invested ₹1,200 crore from internal accruals to scale preform and fiber drawing capacity from 30 million to 50 million fiber kilometers. That vertical integration insulates it from preform price spikes and supports premium margins.
STL's $56 million South Carolina plant is Build America, Buy America-compliant, making it eligible for the $42.45 billion BEAD program while Chinese rivals are locked out. The site specializes in high-density cables for rural broadband and hyperscale markets.
FY24 and FY25 brought net losses of ₹71 crore and ₹72 crore as Chinese overcapacity crushed prices. FY26 swung to ₹56 crore PAT; Q1 FY27 delivered the strongest quarter in company history with 87% revenue growth.
Q1 FY27 profit after tax reached ₹197 crore, up 1,870% year-over-year, with EBITDA margin—a profitability measure—at 20.8%, its highest in nearly 20 quarters. Revenue hit ₹1,910 crore for the quarter.
STL's open order book swelled to a record ₹18,618 crore, including a $1.11 billion AI data center contract and a $288 million hyperscaler deal. Management's Lakshya roadmap targets ₹20,000 crore revenue and 27% EBITDA margin by FY29.
Fiber is cyclical; Chinese overcapacity crushed prices and STL posted losses in FY24 and FY25. The FY29 target needs 4x revenue growth and 1,400 basis points of margin expansion in three years—execution risk is real.
STL has moved from copper cable supplier to a vertically integrated 'Glass-to-Data Center' player shaping AI-era connectivity. Read the full deep dive to see the technology, finances, and risks in detail.
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