A wide range of quantum applications in the fields of cryptography, metrology and photonic computing, can benefit from non-classical light emitters. In particular, the combination of high single-photon purity, brightness and coherence of the emission, is of prime importance. Furthermore, emission wavelength in the standard telecommunication windows around 1310nm (O-band) and 1550nm (C-band), offers, among others, the compatibility with the global fiber network. The thesis at hand presents optical invesitgations of the brightness, single-photon purity and coherence of In(Ga)As quantum dot emission in the telecom O-band and C-band. In-depth investigations allow to draw conclusions on the limitations of the coherence. Advanced, (quasi-)resonant excitation schemes are found to enable highly pure single-photon emission and improved coherence, while the integration into photonic structures allows to combine this with a high brightness.weiterlesen