Evaluation of Shrinkage Forces and Thermal Transitions of Fluorinated Ethylene-Propylene (FEP) Cable Insulations and Buffered Optic Fibers at Low Temperatures
In an attempt to further understand the effects of temperature cycling tight buffered optic fiber cables on proposed connector designs and attenuation losses, several experiments were performed in the IBM-RTP Polymers Laboratory. These initial experiments were made to quantify the amount of shrinkage (if any) which occurs when subjecting fiber optic cable materials to temperatures as low as -40 C. Without any previous experience or known measurements involving shrinkage forces associated with cable insulations, the test procedure includes what is believed to be a novel approach. The cable jackets and fiber buffer insulations were fixed between stationary jaws in an Instron testing apparatus equipped with an environmental test chamber permitting temperature control. Gauge lengths of 6.5 inches and 4.0 inches were used for the Fluorinated Ethylene-Propylene (FEP) tubular samples and polyester elastomer fiber buffers respectively. Typically the Instron chamber temperature was raised as rapidly as possible from ambient to the peak value (+60 C) and then lowered as rapidly as possible to the lowest temperature (0 or -40 C). The temperature cycle was completed by raising the temperature back to ambient conditions. In addition to aiding our understanding of the jacket shrinkage which would affect fiber optic connectors, the experiment helped to develop a sense for the fiber buckling forces associated with temperature cycling. Along with the characteristic force curves which depict changes in force in the temperature ranges of -40 to + 60 C, Differential Scanning Calorimetry (DSC) analysis was conducted on several of the FEP cable and single fiber unit jackets.
