Pattern-effect-free amplification and cross-gain modulation achieved by using ultrafast gain nonlinearity in quantum-dot semiconductor optical amplifiers

We demonstrate that the pattern effect of semiconductor optical amplifiers appearing in amplified signals and in cross-gain modulated signals can be suppressed by using quantum dots as active media. This property, which originates from the ultrafast (less than 3 ps) gain nonlinearity of quantum dots dominated by spectral-hole burning, in principle enables pattern-effect-free operations at up to 160 Gb/s. Experimental confirmation of this property was conducted at 40 Gb/s.