Fiber optics are typically constructed as either basic UV coated fibers (typically 250 micron diameter) or tight buffer coated fiber (typically 900 micron outer diameter). Tight buffer optical fibers are used in many cases where a stand alone optical fiber is desired because the fiber is protected by the tight buffer layer. Many times these tight buffer fibers are bundled into a larger cable, such as a 24 fiber cable, so that many tight buffer fibers can be run together to various locations within an installation.
Such multi-tight buffer fiber cables are constructed of a number of components including a coated central strength member, a first tight buffer fiber optic layer, a second tight buffer fiber optic layer, a layer of aramid yarns and an outer polymer jacket. Such an arrangement is shown in prior art FIG. 1.
In these prior art arrangements, although many tight buffer fiber optic elements are positioned within a single cable with sufficient strength for pulling in the longitudinal direction, such cables are also frequently required to past compression tests to make sure that environmental pressures that cables may be exposed to, do not impinge light passing through the fibers contained therein.
Such compression tests typically pass a portion of cable between two compression plates and apply a pressure of approximately 225-250 lbs load across a 4″ inch longitudinal length of cable (or 100-110 N/cm). A typical compression test for such cables is EIA FOTP 41A (Electronic Industries Alliance—Fiber Optic Testing Procedures).
As shown in Prior art FIG. 2, when the prior art multi-tight buffer fiber optic cables is compressed under such tests, cross-over stress points between fibers in the lower layer and the upper layer, typically result in cables of this design not achieving a 100% pass rate.