Xenpak's future came into question over a specification that demands a cut-out area in the PCB to let it fit many switch or router designs. Xpak and X2 emerged as smaller alternatives.

Christian Urricariet, director of product marketing for Finisar's optics division, said: "We haven't spoken to a Xenpak customer who is happy with it. Board cut-outs are still an impediment to high-volume manufacture."

Malcolm Hay, European marketing manager for Intel's optical products group, said: "The divisions between X2 and Xpak are as much politics as anything else. If you look at them, they target the same place. There are finicky rather than fundamental differences."

Xpak appeared first but was joined by X2, promoted by Agere Systems and Agilent Technologies as well as JDS Uniphase. Agere later decided to step out of the optical components business.

Intel's Hay said; "From the point of view of anyone buying modules, [the split] is bad news. We're joining the two groups so we can help bring them together. We hope to come out with one standard."

Antony Spilman, strategic marketing manager at Agilent, says the reason to develop X2 is in response to the fact that, despite criticism, Xenpak is likely to remain in use for a while. he said: "Xenpak has been designed into a hell of a lot of switches. It is the only thing that supports the full range of optics. Only 20% of customers who would ever want to use it are complaining about the cut-out issue. For that 20%, we conceived X2. We had concerns over Xpak."

The main concern was the height of the Xpak module, due to its thermal design. The main claim behind X2 is that its cooling design is more flexible, making it easier to use on PCI cards inside PC servers.

"There are ongoing discussions to merge the Xpak and X2 efforts but there remain blocking points. Everyone agrees one standard would be preferable but it would have to meet the technical requirements," said Spilman.

Finisar does not see a market for it in either Xpak or X2: it aims to go straight to a third-generation module, XFP, despite its need for 10Gbit/s serial interfaces that are not widely available. Urricariet said: "Xpak and X2 are still to be proven in the market."