Carlyle Group will make the investment in Bharti Airtel#39;s Nxtra Data at a valuation of $1.2 billion. : Bharti Airtel on July 1 said Carlyle Group will buy a 25 percent stake in its data centre business for $235 million. Carlyle Group will make the investment in Bharti Airtel's Nxtra Data at a valuation of $1.2 billion. Bharti Airtel will continue to hold the remaining 75 percent holding in Nxtra Data. Private equity player Carlyle will make the investment though an entity called Comfort Investments II.