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. The total number of cores for a 1pc fiber patch cable is calculated as the number of branches multiplied by the number of cores per branch (if there are no branches, the number of branches = 1). This post will guide you through understanding fiber optic cores and selecting the perfect cable for your needs. Single-mode: A. Fiber core count defines the maximum number of optical terminations or distribution points that a fiber enclosure can support.