The two firms have joined Jupiter as part of plans to build their own global networks and cut data transport costs.
The cable is one of many in which the net's biggest firms, including Google and Microsoft, have recently invested.
"There's a bit of a boom in terms of the internet content providers taking a leading role in the development of new submarine cable systems," said Alan Mauldin, research director at analyst firm Telegeography.
The big net firms were involved in about 16 separate cabling ventures, he said, and used the capacity to handle the massive amounts of data their users generate.
Some projects have already been completed but most are due to start carrying data sometime in the next few years.
The net firms were most interested in joining projects that lay cables across the Pacific, the Atlantic and Asia, he said.