Stealthy startup Stoke Inc. is working with massive Japanese carrier NTT Corp. on fixed/mobile convergence, sources tell Unstrung.

It's not yet clear if the startup is working with the fixed or mobile arm of the operator (or both) or what stage any work is at. But a potential deal with NTT would help explain why the VC community is so high on this particular startup, which has not yet even officially launched.

Earlier this week it came out that Stoke has gathered nearly $20 million in a second round of funding from Sequoia Capital and others (see Stoke Gets Stoked With $20M).

Naturally, the startup is keeping schtum. "We can't comment on any customer activities," says Keith Higgins, head of marketing at Stoke. [Ed. note: This must be a great job, right? Marketing at a secret squirrel startup.]

NTT and NTT DoCoMo Inc. (NYSE: DCM) have been fairly progessive in building out different network types -- such as wireless LAN hotspots -- and DoCoMo already has handsets that support cellular and 802.11 connections. So facilitating better fixed/mobile convergence would be a natural move for the operator.

According to one of our sources, Stoke will bring two boxes to the table. "A service router for session/VPN termination and a seamless mobility box... that would sit at the carrier edge and hand off calls... à la Kineto or Motorola," he says.

— Dan Jones, Site Editor, Unstrung