We propose a novel design of optical buffer to generate slow light based on delay time. In the framework of the nonlinear waveguide, we investigate propagation of solitons through microring resonators. Dynamical control over slow-light solitons is realized via controlling fields generated by bright soliton and Gaussian pulse. The nonlinear dependence of the velocity of the signal on the controlling field is analytically described. The buffering effect is achieved by slowing the optical signal using an external control light source to vary the dispersion characteristic of the medium via microring resonators. A graphical approach with a signal flow graph method is used to derive the optical transfer functions in z-domain of filters. The characteristics of the optical buffer devices including the transmittance and time delay of the through and drop port are simulated. Simulated results show the criteria of achieving slow light in semiconductor microring resonators. Finally, output signal shows the delay time rate by propagation through the semiconductor microring resonators. (C) 2012 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.OE.51.4.044601]