Multi-core fiber (MCF) is an advanced optical fiber technology that embeds multiple light-guiding cores within a single fiber cladding, enabling far greater capacity than traditional fibers. This single structural difference separates indoor butterfly cables (FRP only) from their outdoor, self-supporting counterparts. Butterfly cables almost universally use bend-insensitive single-mode fiber — specifically types covered by the ITU-T G. As it only has one core, installation and management are straightforward. It. From the fiber core and core size to single mode fiber and multimode fiber cables, each type of optical cable serves a specific purpose depending on transmission distance, network requirements, and installation environment.