This amendment adds the OTN mappings for the IEEE 802.3 200Gbit/s and 400Gbit/s Ethernet client signals, adds the eSSM message type for the OSMC, specifies OTSiG-O transport over the FlexO-LR SOTUm interface, and adds reference to two FEC options for OTUk signals. It also provides clarification regarding interfaces where OTUk and OTUCn Section Monitoring overhead is optional, and elaborates on OCh and OTiSA maintenance signals