Structure of One-Core Fiber Optic Cable A one-core fiber optic cable consists of a single optical fiber encased within protective layers. There are different types of fiber optic cables because each type is optimized for specific applications that have unique requirements for bandwidth, transmission distance, and environmental factors. Ever wonder how data zooms across cities and continents at lightning speed? The. The core of a conventional optical fiber is the part of the fiber that guides the light. The core is surrounded by a medium with a lower index of refraction, typically a cladding of a different glass, or plastic. This article will discuss about the differences between single-core, dual-core, and multi-core fiber optic cables.