The outer sheath of the optical fiber cable is divided into different material types. . Whether you are designing and manufacturing a new cable or simply choosing an existing one for data, power, fiber optics, or industrial automation, the outer sheath (jacket) is much more than just a speaking cover to the eye; it is, in fact, an important job holder in mechanical protection. Why is the outer sheath of optical fiber cable important? What are the materials? Optical fiber cables are generally composed of optical fiber cores, cladding, coatings, reinforcing elements, and outer sheaths. But, these do not cover all materials used for fiber optic cables jacketing and there are other plastic materials in addition to these below indicated ones. Depending. As the cable's outermost protective layer, the jacket provides mechanical protection while helping resist moisture, environmental damage, and fire. It is expected to offer adequate mechanical strength, moisture resistance, chemical resistance, thermal stability, and flame-retardant performance to. Our fire resistant/fire survival cables feature a steel wire/steel wire braiding/corrugated steel tape armour to provide mechanical strength.