A direction-switchable transponder of a high speed communications network, e.g., an fiber optic data communications network, is capable of dynamically reversing the data traffic flow of its various communications channels in response to a signal. The signal can specify a number of channels, a channel map, or a required bandwidth. The direction-switchable transponder can receive a signal relating to network bandwidth requirements; select, based on the received signal, one or more fiber optic channels for reversing direction of flow of network traffic; and dynamically and automatically reconfigure the selected fiber optic signal to reverse direction of flow of network traffic. By responding to asymmetric bandwidth requirements, the direction-switchable transponder uses high speed communications network lines more efficiently.