The main function of the fiber cable outer sheath is to protect the optical fibers in the optical cable from external damage. It requires the highest flame retardant rating (UL 910/NFPA 262). Under the blowing of a forced fan, the flame spreads and extinguishes itself. Optical fiber cables typically consist of the fiber core, cladding, coating, strengthening element, and outer sheath. Different types of. An electrical cable sheath is the outermost layer of material that covers the electrical conductor, with the primary functions of insulating and protecting the conductor from environmental impacts such as heat, water, chemicals, and mechanical shocks. While internal components transmit power or data, the sheath ensures the entire cable assembly can survive the environment in which it is placed.