The fabrication and characterization of high speed polymeric modulators are summarized in this paper. Electro-optic polymer modulators, made of a thermally crosslinked polyurethane with Disperse Red 19 side groups, have been fabricated, packaged, and tested for fiber-optic transmission applications. Two waveguide structures, straight channel waveguides and integrated Mach-Zehnder interferometers, were defined by reactive ion etching on corona poled polymer thin films. Microstrip line electrodes were used for wideband frequency response. The modulators have been fiber pigtailed, connectorized, and packaged with single mode optical fibers and wideband RF connectors, and packaged in rugged cases. Modulator performance and stability characteristics including halfwave voltage, frequency response, insertion loss, long term halfwave voltage stability, DC bias stability, and optical power handling capability at 1.3 micrometers wavelength were tested. Applications of the packaged polymer modulators in analog and digital transmission systems were also demonstrated.