Several common cable outer sheath materials are PVC, PE, LSZH, AT and rodent-proof sheath materials. Its primary functions include: While the optical fiber itself remains largely unchanged, the sheath material determines how the cable behaves in fire scenarios, outdoor environments. The main function of the fiber cable outer sheath is to protect the optical fibers in the optical cable from external damage. Understand the Environmental. Sheathings designed to be totally opaque (PVC, silicone) should be considered, and in the case of multi-channel construction, both sender and receiver fibers should be individually sheathed inside a larger common sheathing. While it has nothing to do with sheathing, don't overlook other factors.