PRINCETON, N.J., Dec. 7 -- RCN Corp. has signed an agreement to lease dark fiber capacity from NorthEast Optic Network Inc.'s network in southern New England and White Plains, N.Y. RCN reported that the new fiber link would provide additional diversity and redundancy for its routes from Boston to New York and Springfield, Mass., in addition to backbone connectivity through Connecticut.Under the terms of the agreement, RCN will be provided with a 20-year lease of dark fiber, with all fibers and space to be maintained by NorthEast Optic. NorthEast Optic is a facilities-based carrier leasing high-bandwidth fiber-optic transmission capacity on its interstate, intrastate and local loop network facilities to certified carriers.