Ultra-pure synthetic silica glass

Fewer than ten companies on Earth can turn raw silica into the glass preform from which every metre of optical fibre is drawn. In India, exactly one does it at scale.

That fibre is the physical substrate of the country's 5G rollout, its broadband, and the data-centre buildouts now under construction. The preform — a cylinder of ultra-pure synthetic silica — is the bottleneck raw material for all of it. And as of 2026, most major Indian optical-fibre-cable makers still buy their preform or raw fibre from suppliers abroad in Japan, Germany, the United States and China.

Why it is hard. Optical fibre works only because its glass is almost impossibly clean. Trace metals and water content (OH impurities) must be held to parts-per-billion levels, or light scatters and the signal dies over distance. Achieving that floor is not one skill but a stack: high-purity quartz feedstock, a silicon-tetrachloride precursor, and vapour-phase deposition processes — the four the global industry has relied on since Corning invented Outside Vapour Deposition in 1970 and Bell Labs developed Modified Chemical Vapour Deposition in 1974 — that lay down doped silica soot layer by layer. The doped cylinder is then collapsed and sintered in furnaces at 1,600–2,000°C to exact tolerances, under contamination control tight enough to keep those impurities at bay. Only then can a draw tower pull it into hair-thin fibre. Miss on any one layer and the whole chain fails.

Where India stands. Sterlite Technologies makes glass preform from raw silica at its Aurangabad plant — one of fewer than ten firms worldwide able to, per a 2018 analyst report. Its preform facility, "Gaurav", is described as one of the largest greenfield semiconductor-grade preform plants in the world. STL controls production "one step earlier" than rivals who merely cable up bought-in fibre, holds 50 million fibre-km of optical-fibre capacity, and carries a consolidated order book above Rs 17,000 crore, including a multi-billion-rupee order from a global hyperscaler. Its own patent work — an application with August 2019 priority for a fumed-silica manufacturing system — reaches even into the upstream feedstock process.

The rest of the field is catching up unevenly. Aksh Optifibre, smallest by revenue among the top makers, already runs in-house preform manufacturing. HFCL, the second-largest at 34 million fibre-km and expanding toward 42 million, has historically bought preform and fibre abroad; it has now approved roughly Rs 555 crore in promoter warrants and planned a Rs 580 crore glass-preform facility explicitly to eliminate reliance on foreign raw materials. Beneath the companies sits CSIR's Central Glass & Ceramic Research Institute, which began fibre-optics R&D in the early 1980s to establish indigenous MCVD preform fabrication and remains India's only research lab of its kind, now working with DRDO labs on specialty and high-power fibres — but at laboratory, not commercial, scale.

Why the gap persists. The concentration is structural, running deeper than the preform furnace. Even the mineral feedstock is held abroad: natural high-purity quartz sand for the drawing process comes from suppliers such as Sibelco in the United States and TQC in Norway. India's high-purity silica sand and its SiCl4 precursor synthesis are both still emerging capabilities. A capacity built on imported feedstock and imported preform is exposed at every link.

What it would take. The current moment sharpens the stakes. A 2026 surge in AI-data-centre demand opened an industry-wide supply-demand gap of about 100 million core-km a year, pushing cable lead times to as long as sixty weeks — the longest since the early-2000s build-out. Closing India's gap means turning a single scaled maker plus a lab into several, and building the feedstock and precursor layers beneath them. HFCL's investment is a signal that backward integration, not import, is where the field is now headed.