Ultrafast all-optical three-input Boolean XOR operation for differential phase-shift keying signals using periodically poled lithium niobate

We propose and demonstrate that periodically poled lithium niobate (PPLN) can act as an ultrafast three-input XOR gate for differential phase-shift keying (DPSK) signals based on cascaded sum- and difference-frequency generation. PPLN-based all-optical three-input Boolean XOR operations for $20\mathrm{Gbits}∕\mathrm{s}$ return-to-zero DPSK (RZ-DPSK), $40\mathrm{Gbits}∕\mathrm{s}$ RZ-DPSK, and $20\mathrm{Gbits}∕\mathrm{s}$ non-return-to-zero DPSK signals are all successfully verified in the experiment.