Optical fiber is the core light-carrying element, while an optical cable is the protective assembly that houses one or more optical fibers.

Understanding Optical Fiber

An optical fiber is a thin, hair-like filament made primarily from highly purified silica glass or sometimes plastic, designed to transmit light signals over long distances with minimal loss . It consists of three main parts:

• Core: The central part through which light travels, made of glass or plastic with a high refractive index .
• Cladding: Surrounds the core and has a lower refractive index to ensure total internal reflection, keeping light confined within the core .
• Coating/Buffer: A protective layer of polymer such as acrylate or polyimide that shields the fiber from physical damage without affecting its optical properties . Optical fibers can be single-mode for long-distance transmission or multimode for shorter distances, depending on the core size and light propagation method .

Optical Cable Structure

An optical cable is an assembly that contains one or more optical fibers along with protective layers to ensure durability and performance in various environments . The cable typically includes:

• Strength members: Materials like aramid fibers (e.g., Kevlar) to provide tensile strength .
• Outer jacket: A plastic or polymer sheath that protects the fibers from moisture, abrasion, and environmental hazards .
• Optional fillers or dark glass: Used to reduce crosstalk and prevent light leakage between fibers in bundles . The cable allows optical fibers to be safely installed in buildings, underground, or across long distances without damage.

Manufacturing Process

1. Preform creation: Ultra-pure silica is formed into a cylindrical rod called a preform, which mirrors the fiber's core and cladding structure .
2. Fiber drawing: The preform is heated to around 2,000°C, and a thin strand of fiber is drawn downwards, maintaining a precise diameter of about 125 microns .
3. Coating and cabling: The drawn fiber is coated with protective polymers and then assembled into cables with additional strength and protective layers .

Key Takeaway

Optical fiber is not made from optical cable; rather, the fiber is the fundamental light-transmitting element, and the optical cable is the engineered assembly that houses and protects these fibers for practical use in communication systems .