However, Outside Plant, also known as OSP fiber optic jackets, are suitable to be buried directly underground as the jacket material will be made with a polyethylene jacket. If the fiber is also armored, this provides the level of protection that a conduit would. With these assemblies we mention in this article, the widest point of. A conduit is a protective tube or channel that houses the fiber optic cables, shielding them from moisture, dust, physical stress, and other environmental factors. Conduit also facilitates cable management and ease of maintenance. Unlike underground fiber cables, direct. Underground cables are pulled in conduit that is buried underground, usually 1-1.