Numerical Study of the Small-Signal Modulation Bandwidth of Reflective and Traveling-Wave SOAs

We present a comprehensive numerical model for intrinsic small-signal modulation response of both reflective, and traveling-wave semiconductor optical amplifiers. We investigate the small-signal photon and carrier density spatial distribution, modulation response, and -3 dB bandwidth for uniform and lossless traveling-wave modulation current model. The analysis shows that the current model does not significantly affect the modulation response as long as the modulation frequency is within the bandwidth. One of the most important results of our analysis is the discovery of the bandwidth maximum in case of a reflective semiconductor optical amplifier operating with low to moderate input optical powers and high current densities. The bandwidth can be further improved by choosing the optimal amplifier length.