Optical cables consist of a core, cladding, protective coatings, strength members, and an outer jacket, all designed to transmit light efficiently while protecting the fiber from mechanical and environmental damage.

Core and Cladding

The core is the central part of the fiber that carries light signals. It is made of high-purity glass or plastic and has a high refractive index to enable total internal reflection, which allows light to travel long distances with minimal loss ( ). Surrounding the core is the cladding, a layer of glass or plastic with a slightly lower refractive index that reflects light back into the core, maintaining signal integrity ( ). Core diameters vary: single-mode fibers typically have a 9–10 µm core for long-distance transmission, while multimode fibers have larger cores (50 or 62.5 µm) for shorter distances ( ).

Coatings and Buffer Layers

Each fiber is coated with a resin or polymer layer to protect against physical damage and moisture. This coating does not affect optical properties but provides mechanical strength ( ). Additional buffer layers or core tubes may be added to form the cable core, further safeguarding the fibers from crushing forces and stress during installation ( ).

Strength Members

Optical cables often include strength members made of materials like Kevlar®, steel wires, or fiberglass rods. These components bear tensile loads, prevent stretching, and protect the fibers from mechanical stress, especially in aerial or long-distance installations ( ).

Outer Jacket

The outer jacket is the final protective layer, typically made of durable polymers. It shields the cable from environmental hazards such as moisture, chemicals, abrasion, and UV exposure. Some cables are armored with metallic layers for underground or industrial applications, while others are self-supporting for aerial deployment ( ).

Additional Features

• Ripcords: Facilitate easy removal of the outer jacket for splicing or repairs ( ).
• Light-absorbing layers: In some designs, dark glass is placed between fibers to reduce crosstalk and flare ( ).
• Numerical aperture: Determines the acceptance angle of light entering the fiber, affecting coupling efficiency ( ).

Summary

The structural design of optical cables ensures efficient light transmission, mechanical protection, and environmental resilience. By combining a high-refractive-index core, reflective cladding, protective coatings, strength members, and a robust outer jacket, optical cables can support high-speed, long-distance data communication across diverse applications ( ).