The public knows little about Ren Zhengfei, the former military officer who runs Huawei, China's largest telecom equipment maker. But lack of visibility hasn't stopped Ren from building a global empire that's playing an increasingly important role in running the world's phone and Internet networks: The company estimates it grew 28% to $28 billion in revenue last year. Roughly two-thirds of sales come from non-Chinese customers, including Britain's BT. Huawei's products and services help keep phone and Internet networks around the world up and running. But security concerns have largely kept Ren and his company out of the one market he covets: the U.S. A new R&D center in California may increase Huawei's American presence, but analysts expect Ren himself to maintain his usual low profile.