In selecting a material for an outdoor cable jacket, a manufacturer must choose one that is not only cost-wise, but also one having optimal performance characteristics for the intended environment.
The characteristics considered crucial for a fiber optic cable jacket are toughness, tensile strength, heat and chemical Resistance, flexibility, and long-term environmental stability.
For the best combination of these factors, as well as cost, polyethylene is the material of choice for the vast majority of outside plant cable manufacturers.
Various grades of polyethylene such as low, medium and high density are available for applications requiring specific performance attributes.
Various additives can also be mixed in with the polyethylene resin by the material suppliers to enhance other material properties, as needed, to resist the demands of a specific type of environment.
Carbon black is the most common additive and is used to improve the jacket material's resistance to the effects of solar radiation.
Adding carbon black also gives outside plant cables their characteristic black color.
Other UV stabilizers in limited use allow for jacket colors other than black but may not be as effective.
Some specialized materials can be used to significantly improve the performance of the jacket in the presence of strong electrical fields.
Track-resistant polyethylenes (TRPE) are used to inhibit cable jackets from eroding away when used in aerial applications that require the cable to be installed in areas of high electric field potentials.
Tracking is an electrical phenomenon that occurs when a current induced on the surface of the cable jacket is interrupted, resulting in arcing.
The current is established when water, from rain or fog, is mixed with contaminants in the air such as dust, pollution, salt spray, etc.