Investigation of semiconductor optical amplifier direct modulation speed

In-line and reflective semiconductor optical amplifiers can be advantageously utilized as external modulators because they can perform simultaneously two functions (amplification and modulation). When the SOA is used in next generation access networks the modulation bandwidth is a crucial property, because it will limit the application. In the paper theoretical and experimental investigations are presented with the result of improved modulation bandwidth. The experimental results confirm, that by proper adjustment of the operation point and environmental conditions a significant improvement in the modulation bandwidth is achieved. Mainly the bias current and the level of the incident optical power determine the carrier lifetime. The modulation bandwidth can be doubled by this approach. The theoretical and simulation results represent the effect of the device parameters, like device length and electrode setup. However there is a trade-off between modulation efficiency and modulation bandwidth, which demand circumspect design of the device and system parameters.