the shared fiber and ONTs. Active optical network (AON) architecture. It uses a shared P2P fiber link between the OLT on the telecom operator's side and an active remote switch (sometimes referred to as a curb switch), and P2P links between such active remote switch and ONTs. The active switches do optical-electronic conversion to process data in the switch and vice versa (on the next fiber link). WDM PON architecture. It is P2MP passive optical architecture with applied WDM (which multiplexes several wavelengths per single fiber). The optical networks, including PON architectures, are based on TDM, which is nec- essary to have strict QoS provisioning over the optical network part. Legacy TDM-PON standards (e.g. gigabit PON - GPON) define line bitrates of up to 2.5 Gbit/s and a max- imum length of links of 20 km. Commonly, use splitting for PON is 1 : 32 or 64 (1 64 means that feeder fiber splits to 64 fiber links on the way to end-users); however, up to 1: 128 can be found in the products, but that is limited by optical power available at the ONT. In general, FTTH can carry voice, video (including TV), and Internet data services to end-users. AON and PON multiplex the data on a single wavelength in a given direction, while different wavelengths are used for uplink (i.e. upstream) and downlink (i.e. down- stream). With applied WDM, there is the possibility to carry different types of traffic on different wavelengths (e.g. voice on one wavelength, TV on another). WDM implemen- tations can be based on PON or AON, where initially the more cost-effective solution is WDM-PON because in such cases less active equipment is needed to be deployed in the access network. Also, WDM-PON can be implemented as an upgrade of legacy PON by changing transceivers on both ends of the fiber, OLTs and ONTs. Table 4.4 gives the main PON standards. The PONs with higher bitrates than GPON are referred to as next-generation PON (NG-PON). The standardization of NG-PON is carried out by ITU. The ITU standardization of 10 Gbit/s capable PON 