Analysis of optical DEMUX characteristics based on four-wave mixing in semiconductor optical amplifiers

We have analyzed the basic characteristics of all-optical demultiplexing (DEMUX) based on four-wave mixing (FWM) in semiconductor optical amplifiers (SOAs) by solving a modified nonlinear Schrodinger equation by the finite-difference beam propagation method. Amplified spontaneous emission noise was not included in our model. The optimum pump pulsewidth for obtaining the high ON-OFF ratio is 1~3 ps for 1 ps, 250 Gb/s probe pulses. The shorter limit of the pulsewidth is due to detuning between the pump and probe frequencies, which is determined by the gain bandwidth of the SOA. In order to achieve faster DEMUX operation, an SOA with broader gain bandwidth is required. We also simulated pattern effects in the FWM signal. Power fluctuation in the FWM signal can be reduced by using a strong energy pump pulse and/or weak energy probe pulse. The energy fluctuation of the FWM signal decreases to less than 1% for a 30-bit, 250-Gb/s input probe pulse train with a pulse energy of 0.01 pJ. This small fluctuation should not disturb DEMUX operation. We have also examined DEMUX from time multiplexed signals by repetitive pump pulses. Strong energy pump pulses decrease the FWM signal intensity. However, there is no pattern effect due to gain saturation because the pump pulses are injected continuously