Fiber optic cable in the middle of the fiber optic cable interface

The middle of a fiber optic cable contains the core, a thin strand of glass or plastic that carries light signals. The core is the central component of a fiber optic cable and is responsible for transmitting data in the form of light pulses over long distances. It is typically made of ultra-pure silica glass (SiO2) or, in some cases, plastic, and its diameter is extremely small—often less than a human hair, ranging from 8–10 microns for single-mode fibers to 50–62.

5 microns for multimode fibers. The core's high transparency allows light to travel with minimal loss, making it the essential pathway for optical communication. Surrounding the core is the cladding, a layer with a lower refractive index that reflects light back into the core, ensuring it remains contained and travels efficiently along the fiber.

Outside the cladding, additional layers such as the coating, strengthening fibers (like Kevlar), and the cable jacket provide protection against physical damage, environmental hazards, and mechanical stress. In summary, the core is the heart of a fiber optic cable, enabling the transmission of light signals, while the surrounding layers support and protect it to maintain signal integrity over long distances.