What material is the cladding of optical fiber cables made of

The core of an optical fiber is typically made of glass or plastic, often doped to increase its refractive index, while the cladding is made of a material with a lower refractive index, usually pure or doped silica.Core MaterialThe core is the central part of the fiber that carries light signals. It is most commonly made from high-purity silica glass (SiO₂), which is exceptionally transparent and allows light to travel long distances with minimal loss. To increase the refractive index of the core relative to the cladding, the glass is often doped with materials such as germanium dioxide (GeO₂). In some cases, plastic cores are used, especially for short-distance or flexible applications, made from materials like acrylate or polyimide. The core diameter varies depending on the fiber type: 8–10 µm for single-mode fibers and 50–62.5 µm for multimode fibers .Cladding MaterialThe cladding surrounds the core and has a lower refractive index to ensure total internal reflection, which confines light within the core. In silica fibers, the cladding is usually pure silica or silica doped with elements like fluorine or boron to reduce its refractive index. Some specialized fibers, such as double-clad fibers, may have additional inner cladding layers for guiding pump light in fiber amplifiers. In plastic optical fibers, the cladding is typically made from a fluoride-doped polymer or other plastics with a lower refractive index than the core .SummaryCore: High-purity silica glass or plastic, often doped (e.g., with germanium) to raise refractive index.Cladding: Pure or doped silica, or polymer, with a lower refractive index than the core to confine light. This combination of materials ensures efficient light transmission, minimal signal loss, and proper guidance of optical signals over long distances or in specialized applications .