Abstract
Long-distance submarine cable systems, such as the transoceanic system, generally consist of a series of cables and repeaters. Repeater units are spaced at regular intervals to boost the attenuated optical signal and presently contain optical amplifiers in a pressure vessel made of copper alloy. Since the repeater unit is more massive than the cable, it pulls the cable catenary locally toward the seabed. In the 1990s, several studies numerically simulated cable behavior in the water and showed that the seabed slack runs short, and the seabed cable tension increases just before the repeater reaches the seabed. Therefore, it has been pointed out that an unarmored cable with a polyethylene sheath can be easily damaged. However, no reports have been published regarding the actual situation of cable faults related to the laying of repeaters. This study quantitatively analyzes the mechanism of cable damage related to the laying of repeaters, based on experiments, simulations, maintenance records, and a comparative analysis between the simulation results and actual cable faults. Cost-effective methods to mitigate cable faults triggered by laying a repeater in the deep sea are also explored to ensure mechanical stability during the design lifetime.
Highlights
The first submarine cable, in the 1850s, crossed the English Channel, between England and France, to enable telegraphic communication [1]
Cable Faults in Trenches In order to verify the causes of faults, we reviewed the literature on the cabled seismic observation system near the trench east of Japan and the maintenance records of the fiber-optic submarine cable system
Analysis and comparative evaluation based on experiments, simulations, and submarine cable maintenance records quantitatively demonstrated the cable fault mechanism and actual faults associated with laying repeaters
Summary
The first submarine cable, in the 1850s, crossed the English Channel, between England and France, to enable telegraphic communication [1]. Cables in the 19th century were composed of iron wire wrapped around natural insulation material, such as Gutta-Percha, which surrounded single or multi-strand copper wires at the core. By 2016, the fiber-optic submarine cable system (hereafter referred to as the system), which is not related to cable capacitance, had evolved to a mind-boggling 10 Tbps (terabits per second) of bandwidth per fiber [3]. Without these cables, the internet would quickly hit gridlock, and social activities that depend heavily on digitalized information would be severely restricted. In the East China Sea, off the coast of China, systems are frequently damaged by anchors from fishing activities or shipping industries [5]
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