Optical cables are typically composed of a core, cladding, protective coatings, strength members, and an outer jacket.

Core

The core is the central part of the optical fiber that carries light signals. It is usually made of ultra-pure silica glass (SiO2), though some short-range or cost-sensitive applications use plastic cores. The core's diameter varies depending on the fiber type: single-mode fibers typically have a core of 8–10 microns, while multi-mode fibers range from 50 to 62.5 microns. The core's high purity and precise manufacturing minimize signal loss over long distances .

Cladding

Surrounding the core is the cladding, made of glass or plastic with a lower refractive index than the core. This difference enables total internal reflection, keeping light confined within the core for efficient transmission .

Coating

The coating or primary buffer layer is a protective polymer, often acrylate or polyimide, applied directly to the cladding. It shields the fiber from physical damage, moisture, and microbending, without affecting optical properties .

Strength Members

To prevent stretching and mechanical stress, optical cables include strength members, commonly made of aramid fibers (e.g., Kevlar) or steel in armored cables. These components bear tension and protect the fragile core during installation and operation .

Outer Jacket

The outer jacket is the final protective layer, typically made of plastic or other durable materials, designed to resist environmental factors such as UV exposure, moisture, and abrasion. The jacket type is selected based on the installation environment, whether indoor, outdoor, or underground .

Additional Features

Some optical cables include ripcords for easier jacket removal, dark glass layers to reduce crosstalk, or multiple fibers bundled together in ribbons for high-density applications . Connectors at the ends allow easy connection to transmitting and receiving equipment. In summary, optical cables are carefully engineered assemblies where each component—the core, cladding, coating, strength members, and jacket—plays a critical role in efficient light transmission, mechanical protection, and environmental resilience.