A MECHANICAL MODEL FOR STUDYNG STRESS AND STRAIN CAUSED BY TEMPERATURE VARIATIONS IN FIBRE OPTIC CABLES

摘要

Temperature changes undergone by fibre optic cables lead to variations in size of their elements. These variations and related stresses may cause an increase in attenuation, due to the curvatures created by the difference of the length of the fibre and the secondary protection. The method used to predict this effect is based upon the balance of strengths between the different elements making up the cable, hence it is necessary to determine all the forces involved in this balance (expansion, contraction and friction). Young's modulus and the coefficient of thermal expansion, both depending on the temperature, are the material parameters used to calculate the expansion and contraction stresses in fibre optic cables. A more exact method may be obtained by measuring these stresses directly in an experimental way. This paper shows the results of the above mentioned methods to determine the mechanical stresses linked to temperature changes and a model to study the thermomechanical behaviour of fibre optic cables.