Noise characteristics and optimum fiber length of spectral inversion using four-wave mixing in a dispersion-shifted fiber

An analysis of noise characteristics, described by an effective noise figure, of polarization-sensitive and polarization-insensitive spectral inverters based on four-wave mixing in a dispersion-shifted fiber is given considering the influence of optical filters on noise. It is found that inserting optical filters in the input signal channel and/or in the pump channel can reduce effective noise figure of the spectral inverter, When an optical filter is used in either the input channel or the pump channel, a conversion fiber length of around 20 km, where maximum conversion efficiency is obtained, is required to reduce effective noise figure. However, when optical filters in hath the input signal channel and the pump channel are used, a nearly identical effective noise figure can be obtained for conversion fiber length of longer than 6 km, Furthermore, the effective noise figure of a spectral inverter, unlike that of an optical amplifier, is dependent an system configuration. (C) 1997 Academic Press.