Estimation of BER performance and cascadability of wavelength converters based on cross-gain modulation in semiconductor optical amplifiers

The transmission of the input intensity noise for wavelength converters bas ed on cross-gain modulation in semiconductor optical amplifiers is investig ated theoretically It is shown how the noise statistics change due to the n onlinear transmission function and how bit error rates can be estimated. Th e power penalty strongly depends on the wavelength shift and can be 5.2 dB at 2.5 Gbit/s when the wavelength is up-shifted by 20 nm. When the extincti on ratio is enhanced by the converter, even negative penalties are obtainab le. In agreement with computer simulations, the input dynamic range is dete rmined to be at least 13 dB. Furthermore, it is demonstrated that at 2.5 Gb it/s, 62 wavelength converters can be cascaded when each converter is opera ted so that the extinction ratio is preserved. However, when the wavelength is alternatively down-and up-shifted by 15 nm, less than eight stages are cascadable.