**5. Conclusion**

We have presented a detail numerical analysis of optical phase-conjugate characteristics of the FWM signal pulses generated in SOAs using the FD-BPM. We have shown that the input pump pulsewidth is an important factor in determining the optical phase-conjugate characteristics of the FWM signal pulse. If we use relatively long input pump pulses, nearly ideal phase-conjugate characteristics, within the confines of reversing the chirp of optical pulses, can be obtained even for very short optical probe pulses. From the simulated example, it has been clarified that the nearly ideal phase-conjugate characteristics are obtained for ~2.2 ps chirped probe pulses using a 10 ps pump pulse. When the pulsewidth of pump pulse decreases, the minimum compressed pulsewidth is obtained using the fiber with a smaller β <sup>2</sup> *f f Z* than that of the input fiber. For much shorter pump pulses such as 1 ps, short FWM signals can be obtained via the gating characteristics of the FWM. However, only a part of the phase information is copied to the FWM signal, and the phase information is lost due to the nonlinear effect. Thus, the pulsewidth is not compressed by propagation through a dispersive medium.
