The authors investigate the propagation of picosecond pulses through semiconductor optical amplifiers using the measurement technique of frequency resolved optical gating. The work shows the generation of significant pulse pedestals and frequency chirp across the optical pulses, which initially have a duration of 2 ps. As the input peak power of the optical pulses is increased from 2.4 to 80 mW, the pulse pedestals increased by 20 dB and the chirp became significantly more nonlinear. The generated pedestals and the nonlinear output chirp may cause serious degradation in high-speed communications systems employing wavelength-division-multiplexing and optical time-division-multiplexing techniques.