Cisco MDS 9000 Series Configuration Manual page 230

Configuring X2 DWDM Transceiver Frequency
Step 3
switch(config)# module 1 transceiver-frequency x2-fc
Configures (default) the link to function as X2 FC.
Note This feature is not supported in other than MDS 9134 modules. In MDS 9134 modules, the 10-Gigabit Ethernet
ports must be in down state when you configure the X2 transceiver frequency.
Cisco MDS 9000 Series Fabric Configuration Guide, Release 8.x
208
Configuring Dense Wavelength Division Multiplexing