Poor flame retardancy, unsuitable for indoor or high fire-safety environments. A fiber optic cable jacket is the outermost protective layer of an optical fiber cable. Structurally, a fiber cable comprises the core, cladding, coating, strength member, and outer jacket. Performance has a major impact. Cable. The outer jackets of fiber optic cables come in different material types, each with its inherent characteristics (varying fire resistance) and suitable usage scenarios.