Improving the response of a SOA wavelength converter in the counter propagating mode using a fiber Bragg grating

Abstract

All-optical wavelength conversion using cross-gain modulation in a semiconductor optical amplifier is one of the simplest and most common techniques to perform such operation. However, the finite gain recovery time of the amplifier causes severe distortion and pattern dependence at high bit-rates. The present work shows that it is possible to reduce the pattern dependence of the output converted signal using a fiber Bragg grating operating on its transmission edge. A wavelength converter using the non-linear effect of cross-gain modulation in a semiconductor optical amplifier can be assembled in the co-propagating and counter-propagating modes. The advantage of the counter-propagating mode is the possibility of an assembly without an optical filter in the output of the converter to filter the input signal, however this scheme introduces crosstalk in WDM systems, due to the residual facets reflectivity of the semiconductor optical amplifier. In this paper we analyze by simulation using commercial software, the improvement in the frequency response of a wavelength converter based on cross gain modulation in semiconductor optical amplifier in the counter-propagating mode using a fiber Bragg grating. The simulation results show that, with the fiber Bragg grating in the output of the converter, the pattern dependence of the converted signal is reduced. This paper also shows the advantages and disadvantages of the counter-propagating mode.