Optical cables are composed of a core, cladding, coating, strengthening fibers, and an outer jacket, each serving a critical role in transmitting light signals and protecting the fiber.Core
The core is the central part of the optical fiber that carries light signals. It is typically made of high-purity silica glass (SiO2), though some short-range fibers use plastic cores. The core's diameter varies depending on the fiber type: single-mode fibers have a core around 9 microns, suitable for long-distance, high-bandwidth transmission, while multimode fibers have cores of 50–62.5 microns for shorter distances like campus or indoor networks. The core's refractive index is higher than the surrounding cladding to enable total internal reflection, which keeps light confined within the core for efficient transmission over long distances .
Cladding
Surrounding the core is the cladding, made of glass or polymer with a slightly lower refractive index than the core. This difference in refractive index ensures that light signals reflect back into the core rather than escaping, maintaining signal integrity. The cladding also provides a first layer of protection against physical damage and signal loss .
Coating
The coating is a protective polymer layer applied over the cladding. It cushions the fiber against scratches, moisture, and minor mechanical stresses during handling and installation. Common coatings include acrylate or polyimide, which do not affect the optical properties but significantly enhance durability .
Strengthening Fibers
To prevent stretching and mechanical damage, optical cables include strengthening fibers such as aramid yarn (Kevlar) or steel wires. These fibers bear tension loads, especially in outdoor or long-span installations, and help maintain the fiber's structural integrity under stress .
Outer Jacket
The outer jacket is the external protective layer that shields the cable from environmental hazards such as UV exposure, moisture, chemicals, and physical abrasion. Jackets are made from materials like PVC, polyethylene, or flame-retardant compounds, chosen according to the installation environment and building codes .
Additional Features
Some optical cables include ripcords for easier jacket removal, armoring for extra mechanical protection, or dark glass layers to reduce crosstalk in multi-fiber bundles. These enhancements improve handling, installation, and performance in specialized applications . In summary, an optical cable is a carefully engineered assembly where the core transmits light, the cladding confines it, the coating and strengthening fibers protect it, and the outer jacket shields it from environmental hazards, ensuring reliable, high-speed data transmission over varying distances and conditions .
