Who makes specialty glass & glass fiber for AI data centers

This part covers two related product lines. Optical fiber, drawn from specialty glass preforms, is the physical medium for the network layer's transceivers and cabling (Layer 3) and for site fiber entrance (Layer 9). Separately, low-dielectric-loss glass fabric (T-glass) and, in newer designs, solid glass cores are used inside the substrate that sits under large AI accelerator packages (Layer 1), where they carry high-speed signals between the die and the board with less loss than standard substrate materials. Both draw on specialty glass-melting and fiber-drawing capacity that is distinct from ordinary glass manufacturing and concentrated among a handful of producers. AI clusters are unusually fiber-intensive relative to their size — the scale-out and scale-up network fabric that ties thousands of GPUs together runs on far more fiber per rack than a general-purpose enterprise cluster — and the largest packages are the first to adopt glass-core substrates to keep signal loss down as package sizes grow. For investors, the fiber side is a function of optical-fiber and cable capacity and glass-preform lead times; the substrate side is a smaller, newer market where qualification with a handful of substrate and package makers is the gating step rather than raw material availability.