A brief analysis of recent experimental data reported for radiation-induced responses in directional coupler waveguides is presented. The data are compared with the coupled mode theory for the case of non-synchronous coupling. This analysis is important in understanding undesirable radiation-induced responses in guided wave devices such as cross talk and optical signal attenuation. The radiation-induced responses are examined and shown to be attributal to the alteration of the waveguide propagation and coupling constants. The magnitude of the refractive index change experienced by a directional coupler, which is exposed to a transient electron exposure, is determined from electro-optic theory and found to be consistent with theoretical predictions.