Undersea lightguide cable reliability analyses

A methodology is described to assess the reliability of undersea lightguide cable. The methodology consists of identifying various failure mechanisms associated with lightguide cables and using a mathematical model or experimental data to analyze these failure mechanisms. There are basically four failure mechanisms: fiber fatigue, abrasion, cold flow, and corrosion. As an example, a typical undersea lightguide cable is analyzed to provide an estimate of its reliability. For the 450 cable analyzed, the proof-test strain of the fiber is 1.87% (200 ksi), and the maximum residual strain during service is 0.24% (25.67 ksi). The exponential crack growth model for these conditions predicts a time to failure of 8.322×10⁸ h. The wear model for abrasion shows that the failure time due to abrasion can range from 100 h to 1,000,000 h depending upon the velocity of the cable. The other two failure mechanisms, cold flow and corrosion, have negligible failure rates, because the phosphor bronze tape will protect the insulation material from cold flow damage