Demonstration of 20-Gb/s all-optical XOR gate by four-wave mixing in semiconductor optical amplifier with RZ-DPSK modulated inputs

We propose and demonstrate an all-optical XOR gate at 20 Gb/s using four-wave mixing in a semiconductor optical amplifier (SOA), with return-to-zero differential phase-shifted keying modulated input signals. With such constant intensity modulation format, the patterning-induced degradation in SOA is also alleviated. The proposed scheme is robust and feasible for optical logic operation at ultrahigh speeds.