Optical Digital Signal Processing in a Single SOA Without Assist Probe Light

By exploiting nonlinear effects in a single semiconductor optical amplifier, different functionalities for all-optical digital signal processing applications are implemented. In particular, we demonstrate all-optical exclusive-OR (XOR) logical operation and all-optical binary-to-quaternary ASK format conversion suitable for 2-bit all-optical digital-to-analog conversion (DAC). Both operations are performed without the use of any extra probe light beam. Beside the advantage of reduced complexity in terms of number of active elements the proposed architecture allows to preserve the input signal wavelength at the gate output and is suitable for photonic integration. Error-free operation at 10 Gb/s is demonstrated for the all-optical XOR gate, whereas correct dynamic operation, always at 10 Gb/s is observed for the binary-to-quaternary ASK format converter. Based on the proposed single semiconductor optical amplifier architecture a possible implementation of 3-bit DAC scheme with reduced number of active gates with respect to previously reported schemes is also presented.