Phase noise characteristics of wavelength conversion based on four-wave mixing in semiconductor optical amplifiers and dispersion-shifted fibers

Abstract

A major advantage of the Four Wave Mixing technique for wavelength conversion is its transparency to modulation format. This advantage becomes important for some IP over WDM network realizations where part of the signaling information is an analog or subcarrier modulation approach. In such applications the phase noise characteristics of the conversion process are very important. In this work, a detailed theoretical and experimental study of the additional phase noise induced by the FWM process is presented. The nonlinear elements used in the experiments are semiconductor optical amplifiers as well as dispersion shifted fibers. Two linewidth measuring techniques have been used, the self-homodyne and the beating with a laser source with already known linewidth. The measurements are carried out for different operating conditions (wavelength, pumping level of the nonlinear elements, input power, input signals with different phase noise characteristics, etc). The theoretical interpretation of the above results is based on a modification (inclusion of the influence of the amplified spontaneous emission noise) of an already presented approach which has focused on the mixing process in a resonant optical cavity.