A 4-core fiber optic cable is a type of cable that contains four individual optical fibers within a single protective jacket. These fibers are used to transmit data as light signals, offering high-speed data transfer capabilities over long distances with minimal loss. What is a 4-Core Fiber Cable? A 4-core fiber cable contains four individual strands of glass fibers (cores) protected within a. 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. Fiber is preferred. Before we dive into the details, let's briefly explain what fiber cores are. Made from either high-quality glass or plastic, the core plays a critical role in determining the cable's performance.