Publisher Summary This chapter discusses the important characteristics of fiber optic cable structures, the properties of some of the main types of cable construction, and particular uses of each type. The cable structure is needed to protect the optical fiber from the rigors of the outside world during its installation and throughout its operational life. The cable construction needs to provide features such as mechanical protection for the fibers, and a nonconductive cable for special environments. The cable structure needs to give protection to the fibers against tensile stress, abrasion, cutting, flexing, bending, and crushing experienced during the installation and subsequent operational life of the fibers. It is found that all-dielectric cables are not affected by any form of electromagnetic fields, and are therefore immune to lightning and high voltages that can be caused by power fault conditions. Loose buffering, using either a loose tube or the slotted core construction, is used for most outdoor applications where fibers are likely to be subjected to external stresses, such as tensile forces or extreme temperature change. The four broad application areas into which the fiber optic cables can be classified include aerial cable, underground cable, subaqueous cable, and indoor cable. It is found that outdoor cables and loose tube cables that contain fibers, which are not tightly buffered, need to be spliced to tightly buffered internal cables or patch cords for termination to equipment.