## 2 State of the Art
Each ONU (Optical Network Unit) receives a dedicated WDM wavelength for the maximum data rate. The separation of OAM modes and wavelength is realized in the optical domain to reduce the end-to-end latency. The experimental setupdeals with downlink signal generation and detection. However, there is no possibility for adaptive wavelength and/or bandwidth allocation in relation to real dynamic traffic loading. In [12], a proposal for the LG mode employing the orthogonal OAM excitation is presented. Simultaneously, a DM (Dimensional Multiplexing) PON system that hybridizes OAM-DM based on the WDM and OFDM is proposed. Effects of different wavelengths and different modes on the BER (Bit Error Rate) are discussed at varying transmission distances. Using the WDM principle, optical fibers can be effectively used also for sensor applications. The paper [13] shows the possibility of using long optical paths to power the polarization sensor. The benefits of fiber optic sensors to be exploited in more applications are presented in [14]. Simultaneously, dynamic allocation methods in both bandwidth and wavelength areas utilized in future advanced WDM-PONs are a center of the research interests. In [15], a novel bandwidth allocation scheme is proposed for the PON system that enables the local area network emulation to determine when to switch its work mode. In [16], DWDM-PONs are considered strong candidates for future optical access networks and the next step in access network development. In [17], a solution to enhance the capacity and efficiency of PONs using dynamic spectrum allocation is presented. This solution relies on the WDM technique. The paper [18] is focused on the DWDM technique and its effective utilization in real optical systems and networks and, consequently, in optical access networks. In this research work, a focus is primarily oriented on novel hybrid network topologies considered for WDM-PONs. The main purpose of the contribution [19] is represented by the analysis of possible wavelength scheduling for selected WDM-PON designs with the traffic protection provision. In these designs, only passive optical components in the RN (remote node) location are utilized, and adequate DWA (dynamic wavelength allocation) algorithms are deployed. In [20], the evaluation of resource efficiencies for the non-symmetric dynamic wavelength allocation method applied in the common point-to-multipoint WDM-PON architecture with a conventional topology is presented. This novel wavelength allocation method is oriented towards minimizing the number of working wavelengths that will be used for compliance with customers' requests for data transmission. As can be seen, these OAM and WDM techniques can be combined together for potential increases in the transmission capacity of the optical fiber. This solution can be applied in situations where a high capacity or a high spectral efficiency on short transmission ranges is requested [8; 21]. As introduced, it can be interesting to join these two OAM and WDM approaches. The main aim of this interconnection can lead to possible practical implementation in real passive optical networks. This contribution is oriented to a possible utilization of OAM regimes in advanced WDM-PON optical networks where OAM communication applications are presented in common optical fibers. Also, a novel architecture of WDM-PONs utilizing the OAM technology is proposed. The paper is organized as follows: Section 2 is reserved for the State of the Art. In Section 3, a proposal for the common OAM&WDM-PON design is introduced. A simplified network architecture in the P2 MP (point-to-multipoint) topology is introduced together with the basic principles of optical signal transmission in both OLT and ONT (Optical Network Terminal) terminals. Due to enormous increases in optical fibers' transmission capacities, I focus on the effective utilization of available wavelength and bandwidth resources in the proposed P2 MP OAM&WDM-PON architecture by means of advanced WDM and OAM channel allocation algorithms.