Metromedia Fiber Network, a major provider of optical fiber communications networks in and around large cities, replaced its top executives yesterday and said that it had violated several loan agreements, moving to the brink of bankruptcy. The company missed an $8.1 million interest payment Friday on $231 million in notes issued to Nortel Networks. The missed payment automatically put it into default not just on the Nortel notes but on more than $440 million in notes and other loans from major creditors and banks. As of the end of February, the company had $3.3 billion in total debt and less than $40 million in cash. ... Metromedia Fiber's collapse would be one of the largest yet in the telecommunications sector. The company ... claims to be the industry's leading supplier of high-speed voice and data networks to urban customers. Metromedia Fiber Slides Toward a Bankruptcy Filing | 
