The conventional way of using a nonlinear Fabry-Perot cavity as an optical memory requires a negative pulse input to reset the state of the cavity. The possibility of using positive pulses to turn a system of nonlinear Fabry-Perot cavities on and off is studied and it was found that positive pulse switching is possible in a system of two coupled nonlinear cavities. First, Korpel and Lohmann's proposal of using polarization switching in a single nonlinear birefringent cavity was studied. After a detailed investigation of their proposal it was found that positive pulse switching in a single nonlinear Fabry-Perot cavity is not possible. One of the reasons is that the eigen-polarization states of the output of a nonlinear Fabry-Perot cavity cannot be switched independently. Although it is not possible to switch a single nonlinear Fabry-Perot cavity with positive pulses we were able to use the coupling of the eigen-polarization states to implement other kinds of optical switches which were demonstrated experimentally. The cross-talk effect in a metallic Fabry-Perot cavity was also studied. Next, a steady state model of a system of two coupled nonlinear Fabry-Perot cavities was developed and it was found that positive pulse switching is possible in such a system. The output can be turned on and off either by pulses sent into different cavities or by pulses of different magnitudes sent into one cavity. Finally, the dynamic behavior of the coupled cavities system was modeled by extending Goldstone and Garmire's model of a single cavity with one input to a system of two coupled cavities with two inputs. We verified by numerical calculations that positive pulse switching is also possible in the dynamic regime. / Ph. D.