NEW YORK, June 17 -- FiberNet Telecom Group Inc. , a provider of metropolitan optical connectivity, announced it has executed an agreement to purchase dark fiber from KeySpan Communications, an owner and operator of high-speed fiber optic networks in New York City and Long Island, N.Y. KeySpan Communications is a wholly owned subsidiary of KeySpan Corp. The agreement provides FiberNet with dark fiber connectivity to certain key carrier hotels in the New York metropolitan area.