AbstractThe characteristics of traveling‐wave semiconductor optical amplifiers (TWSOAs) used for the picosecond pulse amplification process are discussed. The distortion of a multigigabit chirped optical pulse train generated from gain‐switched optical transmitters due to a saturation of output power and a gain of TWSOAs is analyzed. The optimized injection current and operating temperature of TWSOAs in amplification of picosecond negatively chirped optical pulses are determined. The shortest optical pulse is found to broaden from 21 ps to 30 ps after amplification by TWSOA. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 202–207, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10276