Katsuyuki Tsuneishi

Long-term reliability of layer-type tight structure cable

The long-term reliability of the optical-fiber strength in the tight structure cable is discussed from the viewpoint of residual fiber strain and prooftesting condition. The maximum fiber strain in the installed tight structure cable was evaluated as 0.05 percent experimentally as the summation of: 1) compressive strain induced by nylon jacketing; 2) added strain during cable; 3) residual strain by cable installation; and 4) thermal strain in the installed condition. Based on these measured residual strains on the typical 12-fiber cable with silicone resin and nylon-coated fiber, the required prooftest level was found to be 0.19 percent in order to guarantee the 10 000-km fiber for 25 years with failure probability less than 10-3.

High-strength long-length single-mode fiber synthesized by the VAD method

Long-length high-strength single-mode fibers were fabricated from large preforms made by the VAD process. The longest piece lengths produced at 2-percent (1.4 GPa) strain prooftesting and 5-percent (3.5 GPa) strain prooftesting are 41.7 km and 15.6 km, respectively. These are the longest length fibers in the world at their respective strain prooftesting levels. The transmission losses for the 41.7-km fiber are 0.36 dB/km at 1.3 μm and 0.22 dB/km at 1.55 μm.