Optical fiber cable for underwater use using terrestrial optical fiber

Abstract

An underwater optical fiber cable is constructed from a terrestrial optical fiber cable by hermetically enclosing the terrestrial optical fiber cable with a hydrogen barrier such as a copper tube or by using a terrestrial optical fiber cable having a hydrogen barrier therein, and by wrapping at least one layer of galvanized armor wires outside of the hydrogen barrier. As so reinforced, the terrestrial optical fiber cable has the strength needed for an underwater optical fiber cable by using relatively inexpensive galvanized armor wires. Although the galvanized armor wires generate hydrogen by contact with water, this hydrogen is prevented from adversely affecting optical fibers in the terrestrial optical fiber cable by the presence of the hydrogen barrier. Advantageously, a standard terrestrial optical fiber cable can be chosen from the many types available including high fiber count designs. Therefore, the flexibility of the core terrestrial cable choices permits system optimization and compatibility of underwater cores with shore cables without a proliferation of limited underwater cable designs. Also, the terrestrial optical fiber cable can be selected to include no hydrogen-generating material inside of the hydrogen barrier. Thus, the optical fiber cable of this invention will inherently have greater long-term reliability and, in the event of a rupture or leak in the hydrogen barrier, will last longer than optical fiber cables using hydrogen-generating material inside of a hydrogen barrier.