# Earthquake-Tolerant Energy-Aware Algorithm for WDM Backbone Network
## 1 Introduction
### Related Work  
#### 1.3.1 Enhancing the Resilience of WDM Networks against Geographical Failures  
The growing reliance on telecommunications has highlighted the importance of managing natural disasters in WDM networks. Network recovery encompasses the process of restoring and reinstating normal operations within a computer network. Various approaches to network recovery can be found in the existing literature. In their work, [PERSON] and [PERSON] [8] introduced a methodology for designing earthquake-resilient networks. Using a local Pareto solution approach, they identified optimal geographical routes to incorporate additional network links, fortifying the network against earthquakes through quantitative risk evaluation. In [9], the authors presented a dynamic algorithm that uses seismic hazard information and geographical maps to add new links to existing network topology, enhancing network robustness within cost constraints. Furthermore, in [11], the authors proposed a comprehensive probabilistic model for geographically correlated failures. The authors employed algorithms to identify the most vulnerable locations in a WDM network, while also introducing a set of algorithms to handle simultaneous failures. [PERSON] and colleagues [12; 13] used mixed-integer linear programming (MILP) to estimate the worst-case geographical locations of disasters that could maximize the capacity of disconnected links. Furthermore, the authors of [14] proposed a node relocation method within the backbone network of India, leveraging real seismic zone information to enhance network survivability through minor adjustments. In [15], the authors proposed a network availability evaluator that compares different traffic protection scenarios for advanced optical network designs, with advanced wavelength division multiplexing being included. Furthermore, the authors of [16] presented a prediction-based fair wavelength and bandwidth allocation algorithm that analyzes various wavelength allocation possibilities in hybrid passive optical networks. In [6], the authors introduced a new power-aware algorithm  
Figure 1: IP over WDM [9]. that uses real seismic information to maintain the tolerant connectivity of the backbone network after a large-scale earthquake. The proposed EAFFB algorithm is a power-aware and seismicity-aware WDM backbone network that defines the minimum number of spare links in the virtual topology to ensure tolerant connectivity. In the same research work, the proposed scheme was evaluated through extensive simulation results using real seismic information provided by the Geodynamic Institute of the National Observatory of Athens, and it was verified that both goals of earthquake tolerance and energy efficiency were achieved. EAFFB achieves this by calculating the minimum number of backup paths for links passing through earthquake-prone regions likely to sustain future damage. As presented in [17], high data-rate transmission over optical fibers faces challenges related to signal deterioration caused by nonlinear impairments, with four-wave mixing (FWM) being a notable concern. Particularly at elevated launch power levels necessary for long-haul transmissions spanning hundreds of kilometers, these nonlinear effects intensify, posing a significant challenge in achieving satisfactory transmission performance. The authors of [18] explored the effective implementation of DWDM in optical systems and networks, emphasizing the mitigation of four-wave mixing (FWM), a significant nonlinearity that can limit the transmission capacity. A simulation model for a 15-channel DWDM system was introduced to analyze FWM's impact on transmitted wavelengths. Performance analyses guide the selection of practical wavelength channels for DWDM communication systems. Although the FWM effect is important, it is not considered in this study so as to have a more fair comparison with our previous work presented in [6].