## 2 Materials and Methods  
A network survivability and protection schemes are really important and necessary in advanced optical networks. From a viewpoint of network operators, a network availability is one of the most important factors that can determine a reliability and survivability of selected traffic protection schemes utilized in passive optical networks. Therefore, our performance analysis is based on the Mean Time to Repair (MTTR) and the Mean Time Between Failure (MTBF) parameters that are often and regularly used for evaluation of passive optical networks in operation and that can be used for proving the feasibility of selected traffic protection schemes [20]. This contribution presents the second step of the research work focused on developing of future passive optical networks with new relevant technologies and related traffic protection schemes. Previous work [20] was devoted to the performance analysis of TDM-PON protection schemes by using the PON Network Availability Evaluator. Considering a moderate upgrade to hybrid passive optical networks, traffic protection schemes play an increasing role simultaneously in a development of modern TDM-PON networks. The best network availability can be reached by the dual-parented Type C protection scheme where all components are redundant. It is an advantageous solution, however, with excessive cost demands. The second-best network availability can be reached by the dual-parented Type B protection scheme. In both cases, many reserve components are utilized, above all the most important OLT terminal. Implicitly, advanced traffic protection schemes for more reliable signal transmission and for the higher-level protection safety in next-generation passive optical networks will be considered. After this work, we receive a decision to expand our simulation tool also for advanced WDM-PON protection schemes. In [21], a comprehensive review of various aspects for WDM-PON technologies is presented. This review includes network architectures, devices, protocols and services proposed for the WDM-PON network deployment. In [22], an efficient resource management approach supporting dynamic bandwidth allocation and sharing downstream wavelengths is proposed for ring WDM-PON architectures. In [23], the ring-based WDM-PON access network with a dual-ring architecture is investigated for providing Rayleigh backscattering noise mitigation and fiber-fault protection. Traffic protection and restoration schemes for advanced hybrid passive optical networks are considered in [24; 25]. In [7], a whole optical distribution network protection using protective interconnection fibers is achieved for the wavelength reusable WDM-PON scheme. In [26], different protection schemes for next generation optical access networks are compared based on an assessment methodology. Depending on requirements from the network operator, an appropriate protection scheme can be recommended for both a greenfield and a brownfield scenario based on the targeted network reliability performance. In [27], a physical layer fault management and a protection system for next generation passive optical networks is considered based on a passive optical coding. This approach is oriented on ring-based long-reach passive optical networks. In [28], an analytical model for estimating a network availability under multiple-link failure scenarios is developed for WDM-networks with shared-link connections. For novel hybrid network topologies considered for WDM-PON network designs with traffic protection provision, a selection and optimization of the wavelength grouping on the physical layer can bring other improvements for effective practical utilization of future passive optical networks [29]. In future next-generation passive optical networks, a deployment of the Dense Wavelength Division Multiplexing (DWDM) technique is also expected in a short time.