The PhD project is centered on the investigation of quantum-dot semiconductor optical amplifier (QD-SOA) for future optical networks. The application of this is twofold. One non-linear application is in the area of high bit rate networks around 40 to 100 Gbit/s for building wavelength converters and 2R regenerators. These units are required in optical networks to overcome blocking issues and to increase the signal quality. Another application is in optical access networks where linear amplifiers are required. QD-SOA could be used here as in-line amplifiers to extend the reach of todays access networks from 20 km up to 60 km.