Photonic Local Oscillators (PLOs) operating at optical wavelengths around 1550 nm have a major importance especially for radio astronomic THz Antenna arrays like the "Atacama Large Millimeter/Submillimeter Array" (ALMA) in Chile. The PLO-Technique allows the distribution of a centrally generated Local Oscillator signal over more than ten kilometres to the Antennas, by using the optical Window for long distance communications where loss in glass fibres is lowest. In this dissertation, PLOs for optical Millimetre-Wave and THz Generation have been developed and fabricated in the frame of the ALMA-Project. The main effort has been focused on the realisation of Travelling-Wave-THz-Photomixers for the optical 1550 nm window that, by contrast to the optical components are not commercially available. The presented results show a clear progress in the application possibilities of 1550 nm-PLOs, in a very wide frequency range that spans from a few GHz up to one THz, thereby covering all frequency bands of the ALMA project and also a part of the spectrum for millimeterwave and THz-Spectroscopy.