What material is commonly used in outdoor fiber optic cables to prevent air pockets?

Water-blocking gels or grease are commonly used in outdoor fiber optic cables to prevent the formation of air pockets that can lead to moisture ingress and potentially damage the fiber. These materials are designed to swell when they come into contact with water, effectively blocking it from reaching the inner components of the cable. This is crucial, as moisture can cause signal degradation, corrosion, and other forms of damage to the optical fibers and their protective layers. The use of such water-blocking materials is essential in maintaining the integrity and performance of outdoor fiber optic installations, especially in environments where water exposure is a concern.

In contrast, foam insulation, plastic sheaths, and hollow conduits serve different functions and do not provide the same level of protection against moisture intrusion. Foam insulation primarily offers thermal protection, plastic sheaths provide an outer protective layer but may not have the moisture-blocking capability of gels or grease, and hollow conduits may refer to the physical structure of the cable but do not interact with moisture in the same way. Therefore, water-blocking gels or grease are specifically designed for the purpose of moisture prevention in outdoor applications.