Analysis of Longitudinal Stress Imparted to Fibers in Twisting an Optical Communication Cable Unit

In the exploratory Fiber Optic (FO) cables used in the Atlanta Fiberguide System Experiment, 12 optical fiber ribbons each containing 12 fibers are stacked one on top of the other to form a rectangular array of 144 optical fibers.1-2 Figure 1 shows a representative cross section of a fiber ribbon and of the 144-fiber optical cable core unit. Just prior to sheathing, the unit is twisted to a given period (lay) in order to improve its bending properties. Moreover, good cable bending properties dictate short lay lengths. However, a short lay length results in high longitudinal (axial) stresses and strains on the optical fibers. In order to obtain high 1503 oooooooooooo Cl OPTICAL FIBER RIBBON r y Jv J JYJTJ' Y U LAAAA/J LJ (J W (J o CJU p r* KJ KJ r LJ