Cross-section diagram of optical cable

An optical cable cross-section typically consists of a central core, cladding, buffer coating, strength members, and an outer protective jacket.

Core and Cladding

The core is the innermost part of the fiber, usually made of ultra-pure glass or plastic, which carries light signals. Surrounding the core is the cladding, a layer with a slightly lower refractive index that confines light within the core through total internal reflection, enabling efficient signal transmission.

Buffer Coating

A buffer coating surrounds the cladding to protect the fiber from mechanical stress, microbending, and environmental damage. There are two main types: Tight-buffered fibers: The coating is applied directly to the fiber, providing a smaller diameter and more flexibility, suitable for indoor applications. Loose-tube fibers: The fiber floats inside a larger tube, often filled with silicone gel to prevent moisture ingress, offering higher tolerance to axial forces and outdoor deployment.

Strength Members

To enhance durability, optical cables include strength members such as Kevlar strands or steel wires. These components absorb tensile forces and protect the fiber from stretching or crushing during installation and operation.

Outer Jacket

The outer jacket is the external protective layer, typically made of polyethylene (PE), polyvinyl chloride (PVC), or other durable materials. It shields the internal components from environmental hazards, abrasion, and rodent damage.

Multi-

Fiber Cables

In multi-fiber cables, multiple fibers are arranged in color-coded bundles within the buffer tubes. Each fiber maintains its own core, cladding, and buffer, while the overall cable may include additional strength members and a single outer jacket for protection.

Step-

Index vs Graded-Index FibersStep-index fibers: Light travels by bouncing sharply between the core and cladding boundaries. Graded-index fibers: The refractive index gradually changes from the core center to the cladding, bending light smoothly toward the center, reducing modal dispersion. This layered design ensures efficient light propagation, mechanical protection, and environmental resilience, making optical cables suitable for high-speed data transmission in telecommunications, internet, and industrial applications.