Fiberinthebox BIDI X2 is a standardized form factor for 10 Gb/s optical fiber transponders that is used for data transfer rates from 10.3 Gb/s to 10.5 Gb/s. It is protocol-specific: Either 10G Ethernet or 10G Fiber Channel versions are available. X2 transponders are used in datacom optical links only (not telecom), and they are smaller than old generation XENPAK transponders.