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. Fiber optic cables are essential to modern networks, enabling high-speed and reliable data transmission. This article. The number of optical cores in an optical fiber is the total number of equipment interfaces multiplied by 2, plus 10% to 20% of the spare quantity, and if the communication mode of the equipment has serial communication and equipment multiplexing, you can reduce the number of cores.