ITU-T experts boost Optical Transport Network beyond 100G

ITU-T members have achieved first-stage approval (“consent”) of a revision to a key ITU-T standard underlying the Optical Transport Network (OTN), signalling the provisional conclusion of a three-year process to enable optical transport at rates higher than 100 Gbit/s.

The 5th edition of Recommendation ITU-T G.709/Y.1331 “Interfaces for the Optical Transport Network” has entered the close of a revision process undertaken by ITU’s standardization expert group responsible for networks, technologies and infrastructures for transport, access and home, ITU-T Study Group 15.

The consent of the revised ITU-T G.709/Y.1331 marks the arrival of a foundational element to the next generation of optical transport, meeting industry demand for increased capacity in metro and long-haul transport networks to support the unceasing growth of video and data traffic.

The revised ITU-T G.709/Y.1331 extends OTN with a new, flexible n x 100G frame format (OTUCn) designed for use at beyond 100G line-side and client-side interfaces.

The OTUCn format can be used for line-side interfaces up to 25.6 Tbit/s, giving system vendors the ability to develop higher-rate OTUCn line-side interfaces at their own pace over the coming 15 to 20 years, in line with market demand and technology availability and independently of progress in standardization.

OTUCn client-side interfaces will use the new, flexible n × 100G FlexO frame format and forward error correction (FEC) combined with the available client optical modules. The initial n × 100G FlexO standard, ITU-T G.709.1, is expected to be approved by the close of 2016. Future n × 200G and n × 400G FlexO standards will be available when next-generation 200G or 400G client optical modules become available.

The revised ITU-T G.709/Y.1331 provides the necessary support for 200G and 400G Ethernet under development within the Institute of Electrical and Electronics Engineers (IEEE). The revision also extends OTN to support the FlexE-unaware, FlexE-aware subrate and FlexE Client services developed by the Optical Internetworking Forum (OIF); in addition introducing the capability to transport frequency and time synchronization information, complementing the similar capability in packet transport networks.

The majority of the initial OTUCn applications to be enabled by ITU-T G.709/Y.1331 will relate to line-side interfaces. Examples of initial OTUCn applications are likely to include:

  • Interconnecting 10+ Tbit/s OTN cross connects via 200G, 300G, 400G, 500G, etc. OTUCn line ports
  • Interconnecting 200G and 400G transponders, which support the emerging 200GE and 400GE services under development in the IEEE 802.3bs project, as well as the emerging subrated n×100G FlexE_Aware services developed by OIF’s FlexE Implementation Agreement project
  • Interconnecting n × 100GE muxponders with 200G, 300G, 400G, 500G, etc. tunnels

More information on ITU-T Study Group 15 can be found on the group’s homepage.

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