###### Abstract
In contrast to the downstream traffic, the upstream traffic in the passive optical network based on the hybrid TDM and WDM technique needs an appropriate MAC protocol for avoiding data collisions between ONU units. In such a case, the OLT terminal collects data from ONU units, makes a decision regarding allocated bandwidths and manages the network. Subsequently, a multiple upstream version of the Interleaved Polling with Adaptive Cycle Time (IPACT) was designed. This algorithm expects that each ONU unit supports all possible allocated wavelengths. In a case that the allocated wavelength is not supported by the ONU, then the next available supported wavelength will be allocated. In [31], an overview on recent developments and progress on standardization in next-generation high-speed passive optical networks is given. An outline of the physical layer as well as the MAC layer functions is discussed. The NG-PON2 network can work in a range of conjugated 100 Gbit/s data rates to provide higher data rates for subscribers. These data rates can also be achieved by multiplexing four wavelengths with the 25 Gbit/s transmission capacity for each. In such a network, the ONU unit needs to be equipped with four fixed wavelength transmitters and must provide a possibility for data transmitting on various wavelengths at the same time depending on the adjusted planning strategy of service network providers. In [32], a novel PON-based architecture is proposed for a mobile backhaul to enhance the connectivity between the neighboring base stations. A tailored MAC protocol and a Dynamic Bandwidth Allocation (DBA) algorithm are introduced to support fast communications between base stations. In the NG-PON2 network, an OLT terminal allocates bandwidth to ONU units by means of the GRANT control messages in the Round Robin (RR) way. In each GRANT message, the OLT terminal determines Transmission Window (TW) periods for each of the four wavelengths assigned to the ONU unit. This resource allocation is determined using a dynamic bandwidth allocation method realized in the OLT terminal. In the moment of receiving the GRANT message, the ONU unit right away transmits its frames to the OLT terminal. After data transmitting, the ONU unit transmits the REPORT gate for reportingits status of the buffer storage to the OLT. For avoiding data overlapping, the Guard Time (GT) is designated to each wavelength for the separation of data transmitting for various ONU units from each other. For the 25 Gbit/s data rate, the \(GT\) parameter is considering 1 \(\upmu\)s; that presents 3.1250 KB in the data space [32]. For assigning a flexible number of wavelengths to the ONU unit in the NG-PON2 network, an effective dynamic bandwidth and wavelength allocation is requested. If the algorithm of dynamic bandwidth and wavelength allocation is not sufficiently effective, a number of wavelengths and the size of the transmission window for each wavelength can be inappropriately assigned. So, an inadequate transmission capacity of wavelengths can be assigned to ONU units with higher traffic loading. In this case, the delay of packets from the ONU unit will be increased. In another case, more wavelengths can be assigned to ONU units with low traffic loading. Subsequently, the \(GT\) data space is close to or larger than the \(TW\) size for each wavelength. As a result, wasteful usage of the upstream bandwidth can influence the network performance by increasing the delay [31; 32]. Therefore, effective dynamic bandwidth and wavelength allocation algorithms considered for NG-PON2 networks are at the center of research interests. In [33], two different DWBA algorithms are proposed for the NG-EPON. DWBA-I is a QoS-based algorithm that has been designed to manage several types of data traffic in NG-EPON networks and performs better than different existing DBA algorithms in terms of packet delay, competition time and packet drop ratio.