Novel scheme of 40 Gb/s all-optical NOT gate based on SOA-assisted Sagnac interferometer

We propose a novel scheme for 40 Gb/s all-optical NOT operation with pseudorandom bit sequences (PRBSs) based on a semiconductor optical amplifier (SOA) assisted Sagnac interferometer. The performance of the NOT gate is analyzed through numerical simulations. With properly designed parameters, a high quality output signal with an extinction ratio (ER) exceeding 17 dB and a Q factor over 18 dB can be achieved. A high quality eye diagram is also achievable, indicating that the amplitude fluctuation of the output signal is effectively reduced. The optimum time offset between the data and probe signals is calculated. For a Q factor of 7.78 dB, the time offset can deviate from the optimum value in a range of about 7 ps. The output pulses are almost distortionless compared with the probe pulse and their shapes are not influenced by the SOA carrier lifetime and the input data power.