OTN Interface Standards for Rates Beyond 100 Gb/s

The optical transport network (OTN) protocol defined by the ITU-T (Recommendation G.709) has become the backbone of service provider long haul and metro networks. Its flexibility has allowed it to support the converged transparent transport for the full variety of both constant bit rate and packet-oriented digital WAN client signals, and its overhead is optimized to reduce the equipment and operational costs for service provider networks. The emerging technologies that enable interface rates beyond 100 Gb/s have created multiple challenges and opportunities for the next generation of OTN. This paper first discusses the challenges and considerations behind the new extension of OTN for rates beyond 100 Gb/s (OTN B100G). This paper then provides a tutorial for the new OTN B100G standard in light of the flexible and modular manner in which it addressed these considerations. This paper also gives a tutorial overview of the new flexible OTN “FlexO” protocol. FlexO was developed as a modular PHY technology for OTN B100G, allowing it to reuse IP and modules from the Ethernet ecosystem. In addition, this paper provides a tutorial overview of the new flexible Ethernet “FlexE” technology from the optical internetworking forum. FlexE provides both an important new client for transport over OTN, and technology that has been incorporated into the OTN B100G standard. The complementary synergies between OTN and 200G/400G Ethernet and FlexE will become apparent.