The core is the central component within a cable that serves as the primary path for electrical current or optical signals. In electrical cables, it refers to the conductor or group of conductors that transmit power or data, while in fiber optic cables, it is the glass element that carries light.
In cable construction, the core is the foundation around which all other structural elements, such as insulation, shielding, fillers, and outer jackets, are applied. It is the main conduit for energy or information transfer, and its design determines key performance factors including electrical efficiency, signal integrity, mechanical flexibility, and durability.
For electrical and communication cables, the core usually consists of one or more copper conductors, chosen for their superior conductivity and low resistance. These conductors may be solid for fixed installations or stranded for greater flexibility. In complex control, data, and AV cables, multiple insulated conductors can be combined into a composite core to handle both power and signal transmission within a single assembly.
In fiber optic cables, the core has a more specialized role, it is the central glass or plastic strand, measured in microns, that transmits light. The size and composition of the core determine whether a cable is singlemode or multimode. Singlemode cores, typically around 9 microns, support long-distance, high-precision transmission, while multimode cores, usually 50 or 62.5 microns, allow multiple light paths for shorter, high-capacity communication links. The optical clarity and geometry of the core directly impact performance parameters such as signal attenuation and bandwidth.
Cable core materials and performance are defined under standards from UL (Underwriters Laboratories), IEEE (Institute of Electrical and Electronics Engineers), and TIA (Telecommunications Industry Association). These organizations establish guidelines for electrical safety, signal performance, and optical efficiency across commercial and industrial cabling applications.
The concept of the cable core originated during the telegraph era, when a single metal wire served as the transmission path for electrical signals. Over time, core designs evolved to include multiple conductors, insulation layers, and shielding to support complex communication and power systems. The introduction of fiber optics in the 20th century revolutionized cabling technology, enabling light-based transmission through ultra-pure glass cores with vastly higher data capacity and lower signal loss.