The present invention relates to a method and system for design and routing in telecommunications networks having transparent elements such as photonic switches. Transparent optical networks transmit signals optically, performing both switching and amplification photonically. As a result, transparent networks may be more economical than conventional "opaque" optical networks that convert signals to electronic form at each network node because they do not require as much equipment for performing optical-electrical conversion. However, transparent networks pose new operational challenges. Physical-layer impairments that are repaired by optical-electrical-optical (OEO) regeneration can accumulate along (transparent) connection paths. To effectively deploy and utilize transparency, mechanisms to assure that impairment-feasible paths exist and can be identified in the network are required. The present invention provides: 1) a method for locating OEO-regeneration capability to assure the existence of impairment-feasible paths in a network and 2) a method for identifying impairment-feasible connection paths in a network of transparent and OEO-capable nodes. The first is a method related to network design, which models the design problem as a variation of a connected dominating set problem. The second is a method related to network routing, which transforms the impairment-aware routing problem into a shortest-path problem in an expanded network. The design methodology of the present invention employs both domination and connectability concepts to enable sparser placement of OEO regeneration capability within networks. Further, the routing methodology of the present invention provides a mechanism for finding feasible routes with respect to impairment constraints while minimizing the use of OEO interfaces to assure such feasibility.