Noise in wavelength conversion using four-wave mixing in semiconductor optical amplifiers

We measure the pump power dependence of efficiency and signal-to-background ratio in wavelength conversion using four-wave mixing in semiconductor optical amplifiers, for different lengths of the device. We show that the efficiency for a l-mm-long amplifier is about 40 dB larger and the signal-to-noise ratio is about 23 dB larger than for a 0.25 mm amplifier. We also show that, unlike the efficiency, for constant ratio between pump- and signal-power, the signal-to-background ratio monotonically increases with the pump Fewer. We show theoretically that this behavior holds for any range of pump-power values.