Abstract: An ultrafast digital optical signal processor includes a body of a third order nonlinear material and three input beams, two beams counterproprogating in the material on-axis and the third beam propagating off-axis, all simultaneously, to generate an output beam that counterpropogates with respect to the off-axis input beams. A set of three voltage controlled spatial light modulators are used for encoding the three input beams in accordance with a three-set Venn diagram based encoding scheme. The output beam is split into two parts which are decoded separately using a mask for one beam part and a spatial light modulator for the other beam part.