# Earthquake-Tolerant Energy-Aware Algorithm for WDM Backbone Network
## 1 Introduction  
### Topic Introduction and Research Objectives  
In recent years, the advent of bandwidth-hungry applications, such as file sharing, cloud storage, and video streaming, has raised energy consumption in telecommunications networks. At the same time, the global energy crisis caused by recent events, such as the war in Ukraine and the international shift to renewable energy sources to combat climate change, has created the need to reduce energy consumption in all sectors. The telecommunication sector itself accounts for over 4% of the world's total energy consumption [1]. Its carbon footprint amounts to 2% of all carbon emissions in the atmosphere [2]. These figures are expected to continue rising in the coming decades due to the continuous growth of bandwidth demand [3]. Thus, the telecommunication sector is not and will not be an insignificant part of the total energy consumption of humanity. It cannot be an exception in the global effort to reduce the amount of energy we use. Additionally, the telecommunications networks can be extremely vulnerable to natural disasters, such as hurricanes, tropical storms, tornadoes, earthquakes, landslides, avalanches, tsunamis, floods, fires, and animal attacks, as well as man-made or technological disasters, such as power outages, human negligence or errors, anchor drag/drops, EMP attacks, nuclear explosion, sabotage, anti-corporate attacks, cyber-attacks, terrorist attacks, or vandalism. The damage the above can cause to the telecommunications networks is of great importance. In this paper, we will focus on natural disasters, such asearthquakes. Earthquakes have devastating effects on telecommunications infrastructure. For example, the 2008 Sichuan earthquake in China destroyed more than 30,000 km of fiber optic cables and 4000 telecommunications headquarters [4], while the 2011 Great East Japan earthquake and tsunami destroyed nearly 1500 telecommunications offices and 700 telecommunications buildings [5]. The significant impact of earthquakes on communication networks necessitates measures to address the issues they cause and their inclusion in network designs. To this end, a large part of research work has focused on finding solutions, where the reduction of energy consumption, the increase of network capacity, and the tolerability of the network to the natural disaster effects, such as earthquakes, are all achieved at the same time. In our previous research work [6], we addressed these main problems of energy consumption and protection of networks from natural disasters by creating a new power-aware algorithm, which makes use of real seismic information to maintain resilient connectivity of the backbone network after a large-scale earthquake while supporting energy efficiency. To this extent, studies of earthquake-tolerant and, at the same time, energy-aware algorithms have been introduced over the years [7; 8], with the example of the EAFFB (Energy-Aware Fiber Fail Bypass) presented in [6]. In this research, an implementation is provided of a new power-aware algorithm, which makes use of real seismic information, to maintain the tolerant connectivity of the backbone network after a large-scale earthquake, while supporting energy efficiency. EAFFB is a power-aware and seismicity-aware WDM backbone network that defines the minimum number of spare links in the virtual topology to maintain connectivity tolerance. Although the EAFFB achieves its goals, it does not examine the case of deactivating links that are not necessary to achieve better energy efficiency. The main improvements that we present in this paper with respect to [6] are the following. First, the main intent of this paper is to evaluate the possibility of achieving significantly better energy efficiency by redesigning an existing network and, at the same time, maintaining the network connectivity and resilience against earthquakes. Specifically, we examine the possibility of the deactivation of existent links in the network to accomplish better energy efficiency.