A 4-core fiber cable contains four individual strands of glass fibers (cores) protected within a single outer jacket. These fibers are used to transmit data as light signals, offering high-speed data transfer capabilities over long distances with minimal loss. Single-mode: A. According to the IBDN standard, we generally recommend using 12 cores for the communication room in each building, and 24 cores for the building room. Of course, this is a general situation, and specific words may consider according to the following criteria. Number of wiring points and switches. In most modern applications, these are Single-Mode (G.