## 8 Conclusions  
In this contribution, possible traffic protection schemes for common wavelength division multiplexing-based passive optical networks are presented, analyzed and evaluated. We realized reliability block diagrams suitable for network availability considerations for WDM-PON protection schemes. We created and adjusted formulas for calculation of the total network availability in specific protection scenarios. Before the performance analysis, we evaluated and analyzed optical power budget considerations for WDM-PON protection schemes. This is a strong recommendation for any other network designs. Figure 10: The network availability of RING WDM-PON protection scenarios for different numbers of elements. For evaluating possible network migration scenarios related to protection schemes and for comparing of protection possibilities of various passive optical networks, we proposed, modified and extended the PON Network Availability Evaluator simulation tool. Comparing to a previous performance analysis of TDM-PON protection schemes, the PON Network Availability Evaluator must be upgraded for obtaining relevant results appropriate for the performance analysis of WDM-PON protection schemes. This program incorporates all relationships and connections between optical components with their relevant parameters and real values according network operators' demands necessary for evaluating a network availability in WDM-PON protection scenarios. Subsequently, we realized the performance analysis by means of the PON Network Availability Evaluator. The performance analysis is based on corresponding reliability block diagrams and optical power budget considerations and on specific parameters used for the calculation of the total network availability for each considered WDM-PON protection scheme. Based on selected specific parameters, various considered presumptive scenarios of P2 MP and/or RING WDM-PON protection schemes can be evaluated and compared from a viewpoint of the network availability. Presented simulation results of the network availability for WDM-PON protection schemes are analyzed and evaluated from a viewpoint of their practical utilization and implementation. The evaluation of the WDM-PON network availability consists of three parts. In the first part, the highest network availability for P2 MP protection scenarios is reached by the Type C protection. Other considered protections reach similar results, whereby the worst scenario is an unprotected network. In addition, network availability dependencies on restoration times can be obtained for any considered protection scheme. In the second part, a comparison of original and advanced passive optical networks is possible due to the same P2 MP architecture. Better resultant values of the network availability are reached in the TDM-PON network representing a more simple system with a smaller number of simpler network components. For P2 MP WDM-PON protection scenarios, the dual-parented Type B protection is suitable for a practical utilization due to higher protection of several network components. In the third part, better resultant values of the network availability are reached in protected network scenarios compared to unprotected networks. For the WDM-PON practical utilization, the protected metro-access network is more suitable due to a higher number of users than the access only network. In addition, network availability dependencies on different numbers of relevant optical elements can be acquired for protections of any network type. By this way, a practical significance of our research along with its practical applications can be presented. This work was funded by Kultivma a Edukacna Grantova Agentura MSVVaS SR, Grant No. KEGA 034 STU-4/2021. **Institutional Review Board Statement:** Not applicable. **Informed Consent Statement:** Not applicable. **Data Availability Statement:** Not applicable. **Conflicts of Interest:** The author declares no conflict of interest.