What type of protective layer is typically found around fiber optic cables?

Fiber optic cables are designed with a protective outer layer that serves several important functions, which is why the choice of a plastic or other durable material outer jacket is the correct answer. This outer jacket provides essential protection against environmental factors, such as moisture, chemicals, and physical impact, which can damage the delicate fiber strands inside.

The outer jacket is typically made from resilient materials like PVC (polyvinyl chloride) or polyethylene, which are engineered to withstand various conditions while still maintaining flexibility and durability. This design ensures that the inner fibers remain intact and operational even in challenging installations, such as outdoor settings or industrial environments.

In contrast, other options do not adequately encapsulate the primary material used in fiber optic cable construction. For example, metal casings are more suited for electrical wiring and are not commonly used in fiber optics due to weight and rigidity, while rubber insulation could suggest a different type of cable not specifically designed for fiber optics. A glass sheath is not practical for fiber optic cables either, as it would not provide the necessary durability and protection, and glass is typically the material used for the fibers themselves, not the protective layer.