There is no standard defined for 2.5 Gbit/s or 5 Gbit/s via fiber. And - that's the current opinion of IEEE - there is no need for it, because standard IEEE 802.3bz for 2.5 and 5 Gbit/s via copper also defines the PHY with the interface to the PMD. As transceiver FiberChannel transceivers are used. This is not unusual, because Fast Ethernet in the past has used FDDI transceiver or ATM transceivers. Nevertheless Hirschmann is in discussion to convince IEEE to issue a standard to guarantee a certain compatibility and to spare such questions.