A simplex optical fiber cable of this invention includes an optical fiber, a buffer preferably of nylon, surrounding and in contact with the optical fiber, a yarn layer with strength fibers, preferably aramid fibers, disposed about the buffer and a sheath preferably formed of polyvinyl chloride (PVC) surrounding and in contact with the yarn layer. In cross-section, the simplex optical fiber cable has a diameter less than 2.0 millimeters (mm), and thus is much smaller in diameter than optical fiber cables presently available. Preferably, if the buffer is relatively tin providing limited protection to the optical fiber, a slick substance such as talc is applied to an outer surface of the buffer before the yam layer is disposed thereon. The slick substance allows the buffer of the optical fiber to slide to a degree in contact with the yarn layer and thus reduces fatigue caused by axial movement of a ferrule of the connector terminating the optical fiber cable. On the other hand, if the buffer is relatively thick, a friction-reducing substance such as Modaflo.TM. can be applied to the optical fiber to allow the buffer to be stripped relatively easily. A zip-cord duplex optical fiber cable of this invention includes essentially two simplex optical fiber cables with their respective sheaths joining at a middle portion along the axial length of the simplex optical fiber cables. Thus, in cross-section, the zip-cord duplex optical fiber cable has a figure-eight shape with a relatively thin portion in the middle which can be manually pulled apart to separate the zip-cord duplex optical fiber cable into separate simplex optical fiber cables. This feature of the invention allows the zip-cord duplex optical fiber cable to be split at its ends to allow connectors attached to respective ends of the optical fiber cables for connection to respective spaced connector receptacles. A second duplex optical fiber cable of this invention includes two simplex optical fiber cables arranged side-by-side with an oversheath extruded about and holding together the two simplex optical fiber cables. In cross-section, the two duplex optical fiber cables of this invention are less than 2.0 mm in height and 4.0 mm in width, and thus are much smaller than currently available duplex optical fiber cables. The invention also includes die assemblies and methods for making the simplex and duplex optical fiber cables.