A simple rule is that each device needs two cores—one for sending and one for receiving data. Fiber cores are the heart of fiber optic cables, transmitting light signals that carry data. The total number of cores for a 1pc fiber patch cable is calculated as the number of. 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. If. Common fiber cores include 1 core, 2 cores, 6 cores, 8 cores, etc.