Working with small and mid-sized businesses, XO Communications, a competitive local-exchange carrier (CLEC), made an early name for itself by investing in the development of metropolitan fiber-optic ring networks connected by a Tier 1 fiber backbone network stretching across the U.S. But after its cash supply ran dry, the company was forced to undergo Chapter 11 bankruptcy protection in June 2002, emerging in 2003 after financier Carl Icahn took a controlling share.