The three typical structures of optical fiber cables are

Optical fiber cables transmit data as light through a core surrounded by cladding, protective coatings, and strength members, offering high-speed, low-loss communication over long distances.Core ComponentsCore: The core is the central glass or plastic strand that carries light signals. It is made of ultra-pure silica (SiO2) with dopants like germanium to adjust the refractive index, enabling total internal reflection for efficient light transmission. Core diameters vary: single-mode fibers typically have 8–10 µm cores for long-distance, high-bandwidth transmission, while multimode fibers have 50–62.5 µm cores for shorter distances .Cladding: Surrounding the core, the cladding has a lower refractive index to reflect light back into the core, maintaining signal integrity. This layer ensures minimal signal loss and prevents light leakage between fibers .Coating: A protective polymer layer, often acrylate or polyimide, surrounds the cladding to shield the fiber from physical damage, moisture, and microbending. It does not affect optical properties but enhances durability .Strength Members: Materials like aramid yarns (Kevlar®), fiberglass rods, or galvanized steel wires provide tensile strength, prevent stretching, and protect fibers from mechanical stress. Aramid yarns are lightweight yet strong, while steel wires are used for high-tension outdoor applications .Cable Jacket: The outermost layer protects the cable from environmental hazards such as UV exposure, moisture, and abrasion. Jacket materials vary depending on indoor or outdoor use, with armored jackets for underground or aerial installations .Types of Optical FibersSingle-Mode Fiber (SMF): Core diameter ~9 µm, used for long-distance communication with minimal dispersion. Light travels in a single path, reducing signal loss .Multimode Fiber (MMF): Core diameter 50–62.5 µm, suitable for short-distance applications. Light travels in multiple paths, which can cause modal dispersion .CharacteristicsHigh-Speed Transmission: Optical fibers transmit data at near-light speed in glass (~180,000–200,000 km/s), resulting in low latency (~5–5.5 µs per km), .Low Signal Loss: Attenuation is measured in dB/km. Modern fibers have ~3 dB/km at 850 nm and ~1 dB/km at 1300 nm for multimode fibers .Electromagnetic Immunity: Unlike metal cables, optical fibers are immune to electromagnetic interference, ensuring stable signal quality .Durability: Protective coatings, strength members, and jackets allow fibers to withstand mechanical stress, temperature variations (-60° to +80°C), and environmental exposure .SummaryOptical fiber cables are engineered for efficient, high-speed, and reliable data transmission. Their layered structure—core, cladding, coating, strength members, and jacket—ensures signal integrity, mechanical protection, and adaptability to various installation environments. Selection of fiber type, core size, and protective materials depends on the application, distance, and environmental conditions.