What is the difference between XENPAK, XPAK and X2 ?

The X2 with the same function as Xenpak, but with a smaller size that allows more port density. Figure 1 and the below list shows the comparison between XENPAK and X2 optics. Figure 1 Typical Xenpak,XPAK vs X2 A brief comparison between XENPAK and X2

Transceivers	X2	XPAK	XENPAK
Mechanical Dimension	Smallest	Bigger	Biggest
Data Rate	10Gb/s	10Gb/s	10Gb/s
Types	CX4,SR,LR,LRM,ER, ZR,CWDM,DWDM	CX4,SR,LR,LRM,ER, ZR,CWDM,DWDM	CX4,SR,LR,LRM,ER, ZR,CWDM,DWDM
Interface	XAUI	XAUI	XAUI
Standard	X2 MSA	XPAK MSA	XENPAK MSA
Connector	Copper or SC	Copper or SC	Copper or SC
Price	A litter lower	NA	higher