A CW signal experiences a time-varying gain when it co-propagates with pulsed pump in a semiconductor optical amplifier (SOA) due to cross gain modulation, and this can be used to experimentally measure gain recovery time. In this study, we establish a linear relation between the measured gain recovery time and the carrier lifetime of SOAs through detailed numerical simulations of a cross-gain modulated system. The small signal gain and the saturation power are determined experimentally. We also study the dependence of gain recovery time on the pump pulse widths which are smaller than the carrier lifetime and on the CW power. These studies help in an accurate estimation of carrier lifetime of a packaged SOA device. © 2021 SPIE.