The fixed access telecom industry is in transition from 3rd-Generation PON (1-2.5G PON, including GPON and GEPON) to 4th Generation PON (10G PON, including XG-PON, XGS-PON, 10G EPON, and NG-PON2). XGS-PON is now leading in this transition. The next step in the roadmap is 50G PON. This will mark a significant change in the architecture of PON OLT and ONT transceivers. 100G, 200G and even faster PONs are in the research phase. Other PONs are also proposed, but outside the mainstream.