The effect of carrier transport on the dynamic performance of gain-saturation wavelength conversion in MQW semiconductor optical amplifiers

This paper investigates the effect of carrier transport on the dynamic properties of wavelength conversion using gain-saturation in semiconductor optical amplifiers (SOA's). It is shown that the carrier transport slows the rise time of the probe optical power by about 10 ps, but the fall time of the probe power is not significantly slowed. However, the dynamics of the probe chirp are slowed by as much as 30-50 ps when operating at 5 Gb/s. The effect of the modified chirp dynamics due to transport is shown to give an additional dispersion penalty, but this is always less than 1 dB. Electrical feedforward of the optical signal input into the SOA is shown to improve extinction ratio of the conversion process. Carrier transport degrades performance of this scheme by up to 3 dB at high data rates. These results show that it is important to take the chirp performance of SOA's into account when designing them for long-haul communications.