A system or corresponding method provides for communicating data in confined waveguides containing a fluid. The system includes processing and transmitter/receiver operations at nodes in or alone the confined waveguides and transducers to produce a propagation signal that transmits modulated data via the fluid in the confined waveguide. Applications include sensing information about the fluid, such as the pressure, pH, or other parameter(s), and transmitting that data via the fluid in the confined waveguide. For example, the system may be distributed about an oil pipeline or network of oil pipelines. Nodes in the system may include turbines that generate power for use by the nodes at levels sufficient to support the node for its activities. Signal processing and multiple transducers at each node may be employed to extend distances up to kilometers between nodes for low-cost operation of the system.