We studied the potentials of All Optical Switches (AOS) based on the intensity-dependent coupling and decoupling of light into the SPP modes (Surface Plasmon Polaritons) of a sinusoidally corrugated thin metal film (TMF), due to Kerr induced refractive index changes of the surrounding dielectrics. The ideal device has two spatially separated outputs, collecting the reflected and transmitted light and the active volume can be as small as 10(-2) mm(3). Gold and PTS (poly-(2,4-hexadiyne-1,6-diol bis(p-toluene sulfonate) are the materials considered. Losses are limited to 1.5 dB,while a 20 dB extinction ratio per gate has been theoretically demonstrated with signal pulsewidths of 5-10 ps , using a maximum optical switching peak power of 11 kW.