Hi there: I'm doing the final project of my course entitled "Signal Processing With Semiconductor Optical Amplifiers". I'm testing a XOR gate that makes use of the XGM effects in SOAs. The configuration uses two SOAs and two signals (A and B) in a counter-propagation scheme (one act as pump and the other a probe - the signals change their roles in the two SOAs). So, at the output of each SOA i will have the logic operations NOT(A)*B - SOA 1 - and A*NOT(B) - SOA2. I want to combine them (3dB coupler) in order to perform the logic XOR operation. My prolem is that at the SOAs output signals will also have phase information, due to XPM. So, at the coupler there will be interference due to XPM. I tried sum up the signals neglecting the XPM effect and it gave me the expected results. Although this is not realistic. How can i overcome this probem? By the way, my analysis is through MATLAB simulation. Thanks in advance.