Optical cable structure includes

An optical cable consists of a core, cladding, coating, strength members, and an outer jacket, each serving a specific role in transmitting light signals and protecting the fiber.

Core

The core is the central part of the optical fiber that carries light signals encoded with data. It is typically made of ultra-pure silica glass or, in some cost-sensitive applications, plastic polymer. The core's diameter varies depending on the fiber type: single-mode fibers usually have a core of 8–10 microns (commonly 9 µm), while multimode fibers range from 50 to 62.5 microns. The core's refractive index is higher than the surrounding cladding, enabling total internal reflection for efficient light transmission over long distances with minimal signal loss .

Cladding

Surrounding the core is the cladding, made of glass with a slightly lower refractive index than the core. This difference ensures that light remains confined within the core through total internal reflection. The cladding also provides mechanical protection and helps maintain signal integrity. In practical fibers, the cladding is often coated with a thin layer of acrylate polymer or polyimide to prevent damage during handling .

Coating

The coating or buffer layer covers the cladding and core, providing additional protection against physical stress, moisture, and microbending. Coatings are typically made of plastic and can range from 250 to 900 microns in thickness. This layer ensures the fiber remains intact during installation and operation .

Strength Members

To enhance durability, optical cables include strength members, which can be made of Kevlar®, fiberglass, or steel wires. These components absorb tensile forces, prevent stretching, and protect the fiber from crushing or bending stresses, especially in outdoor or long-distance installations .

Outer Jacket

The outer jacket is the external protective layer that shields the fiber from environmental hazards such as moisture, UV exposure, and mechanical damage. Jackets are made from materials like PVC, polyethylene, or flame-retardant compounds, and their color often indicates the fiber type (e.g., orange for multimode, yellow for single-mode). The jacket also facilitates handling and installation .

Additional Features

Some optical cables include ripcords for easy jacket removal, armoring for extra protection in harsh environments, and bundled fiber arrangements to reduce crosstalk and improve performance in multi-fiber cables .

Summary

The optical cable's structure is carefully designed to transmit light efficiently while protecting fragile fibers. The combination of core, cladding, coating, strength members, and outer jacket ensures high-speed, long-distance data transmission with minimal signal loss and robust mechanical resilience .