Subrating and multiplexing non-standard rates in ZR and ZR+ optical interfaces

A ZR or ZR+ interface includes circuitry configured to receive one or more client signals; and circuitry configured to transmit the one or more client signals as an aggregate signal in a Flexible Ethernet (FlexE) format in one of a ZR format and a ZR+ format, including a mapping indicative of how the one or more client signals are one of multiplexed and subrated into the aggregate signal. The aggregate signal can have a rate that does not correspond to a standard Ethernet Physical Medium Dependent (PMD). The FlexE format can include a plurality of FlexE instances with at least one of the FlexE instances having calendar slots removed for a subrating application.