Residual elongations of submarine optical-fiber cable laid on the sea bottom

Fiber elongations during laying and residual fiber-elongation strain after laying of submarine optical-fiber cables have been reported. The fiber elongations have been measured by the optical-pulse-delay method. It has been found that the residual fiber-elongation strains are closely related to cable slack and the cable tension at the sea bottom. Therefore, the residual strains can be minimized by controlling the slack and the tension. The relation between necessary proof-test strain and allowed residual strain has also been mentioned. If the proof-test strain is 1 percent, the allowed residual strain due to laying becomes 0.26 percent.