**Acknowledgement**

The authors would like to thank Dr. T. Kawazoe and Mr. Y. Yamayoshi for their helpful contribution to this work.

#### **6. References**

106 Optical Communication

**5. Conclusion** 

with a smaller

**Author details** 

Hitoshi Kawaguchi

Mohammad Razaghi

**Acknowledgement** 

contribution to this work.

Narottam Das

β

through a dispersive medium.

The spectra and phase in the frequency domain of the FWM signal pulse at the output end of the dispersion compensation fiber, shown as the position D in Fig. 7, are shown in Fig. 12 with the spectra and phase for the ideal case. For the 10 ps pump pulsewidth, the spectrum is almost identical to the ideal case except for the center frequency. The red shift of the center frequency originates from the gain spectrum of the SOAs. For the shorter pump pulse of 1 ps, the spectral width increased because the pulsewidth of the FWM signal becomes short, as shown in Fig. 11(a). From the figure, the output signal phase becomes nearly constant when the input pump pulsewidth is 10 ps. As a result of this simulation (modeling results), we can conclude that pump pulses longer than 10 ps are needed in order to obtain

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

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

*Department of Electrical and Computer Engineering, Curtin University, Australia* 

*Graduate School of Materials Science, Nara Institute of Science and Technology, Japan* 

*Department of Electrical and Computer Engineering, University of Kurdistan, Iran* 

The authors would like to thank Dr. T. Kawazoe and Mr. Y. Yamayoshi for their helpful

*School of Engineering, Edith Cowan University, Australia* 

<sup>2</sup> *f f Z* than that of the input fiber. For much shorter pump pulses such as 1

nearly ideal optical phase-conjugate characteristics for the ~2.2 ps chirped pulse.


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