Physical Characterization of Fibre Optic Cable using Simple Laboratory Stress Tests

Abstract

Most learning institutions in Zimbabwe use fibre optic cable for internet connectivity and the heavy human and vehicular traffic at these places may pose a threat to maintenance of the cable particularly on semi-rigid ground. Physical stress in form of pressure exerted on the cable by the said traffic need to be investigated and compared in relation to tensile strength of the cable. The cables are made of polymers which provide a good operating temperature, chemical resistance, bio compatibility and prevention to mechanical and chemical damage. Simple Physics lab tests offer an opportunity to investigate the stress and strain parameters of the cable. The study sought to determine the Young modulus of the fibre optic cable at Great Zimbabwe University using two methods namely : the centre span deflection method and the strain gauge method. The first method was based on adding standard weights to cable tied on horizontally on two ends and observing deflections from the equilibrium position, the second method involved adding standard weights to a vertically suspended fibre optic and observing extensions from original length. Results of the two methods were processed in linear equations which estimated a Young modulus constant for the cable which is a stress parameter that indicated the strength of the cable. The values for Young modulus for center span deflection method using three specimens of different lengths were 8.67 × 1010 N/m2, 2.34 × 1011 N/m2 and 1.78 × 1011 N/m2 with 0.003% error. For the strain gauge method readings obtained from two specimens of different lengths were 6.48 × 106 N/m2, 9.47 × 106 N/m2 with 0.3% error. Method 1 however gave values that are close to the literature figures and can be relied on to provide stress indicator values.