A simple rule is that each device needs two cores—one for sending and one for receiving data. (actually use a four core optical cable) This is because apart from one-core optical fiber, there are basically no optical cables with an odd number of cores, such as three-core, five-core, etc. The total number of cores for a 1pc fiber patch cable is calculated as the number of. Common fiber cores include 1 core, 2 cores, 6 cores, 8 cores, etc. When selecting fiber, the first step is to determine single mode or multimode, and. Fiber optic cables consist of multiple thin strands of glass or plastic, known as “cores. ” These cores carry the data signals via light.