This field is used to distinguish between different types of DWDM transceivers and different power and environmental classes. The defined identifier values are: Bits 7..6: 00: Power Level 1 Module (1.5 W max. power dissipation.) 01: Power Level 2 Module (2.5W Max) 10: Power Level 3 Module (3.5W max. power dissipation.) 11: Power Level 4 Module (>3.5W max. power dissipation.) Bit 5: CDR exist 0: Module with CDR function 1: Non-CDR version of XFP Bits 5: TX ref clock is required 0: TX Ref Clock Input Required 1: TX Ref Clock Input Not Required Bits 3: CLEI code is present 0: No CLEI code present in Table 02h 1: CLEI code present in Table 02h Bits 2..0: Resesrved