Analysis of frequency chirping of optical phase conjugate signals by four-wave mixing in light-holding SOAs

We propose to use an additional injection beam of short wavelength to enhance the wavelength conversion that utilizes the four-wave-mixing (FWM) effect in a semiconductor optical amplifier (SOA). With this scheme, an assist light can increase the saturation intensity without sacrificing the gain of a SOA, and this leads to an increase in conversion efficiency. A numerical method dealing with FWN, amplified spontaneous emission noise, longitudinal spatial hole burning, wavelength dependent gain spectrum is developed to predict the static and dynamic characteristics of our scheme. The effects of holding light on extinction ratio and chirp dynamics are analyzed in detail. High-pump and/or low-signal power is shown to be effective in maximizing extinction ratio and minimizing peak frequency chirp.