Survivability is one of the most important requirements in design of communications networks, since we as a society are increasingly relying on the Internet, and service interruptions are very costly. Unfortunately, submarine fibre-optic networks are vulnerable to unpredictable disasters, such as earthquakes or nuclear explosions, which pose significant large-scale threats to the submarine cables of modern telecommunication networks.In this paper, we formulate an optimization problem on the plane to minimize the total cable cost under the survivability constraints. We consider at first a simple example of a network of two nodes located on two different islands and propose a rectangular topology network to reduce the probability that all the cables are damaged simultaneously by a single disaster. Then we consider cases of multiple cables, rectangular with rounded corners and rhombus network topologies. Analytical results, validated by simulations, for the survivability of all topology cases are presented including a comparison of the various topologies. Finally, we extend the discussion to a network with an arbitrary number of nodes and a general geography, and to various scenarios of different disaster and cable break probability functions. Overall, this paper provides a methodology for discussing and solving a real world problem.
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