Chirped pulse in traveling-wave semiconductor optical amplifier

We study the results of picosecond optical pulse train amplified by a traveling-wave semiconductor optical amplifier (TWSOA). The distortion of multi-Gigabit optical carriers or pulses generated from gain-switched optical transmitters due to the nonlinear phenomenon inherent in the TWSOA is discussed. The trend in saturation of output power and gain of the optical pulses is observed. The effect of injection current and operating temperatures on the performance of TWSOA in amplification of picosecond negatively chirped optical pulses from gain-switched laser diode with gigabit repetition rate are characterized. Optimal conditions of injection current and operating temperature for the TWSOA are determined, and those for the gain-switched optical transmitter at below threshold and lower than room temperature are obtained. The shortest pulse generated from gain-switched optical transmitter is found to be distorted from 21 ps to 30 ps after amplifying by TWSOA.