Optical A=D converter usable at frequencies above 1 GHz - phase-shifts optical signals of coherent laser source after vertical and horizontal polarisation

摘要

After distribution to the digitising stages, the optical signals are separated according to their polarisation. Thus each optical signal from a laser source is separated into horizontally and vertically polarised components. Then the phase of an optical signal of one polarisation is shifted, while the orthogonally polarised signal component remains unchanged. Both optical signals are resolved by a 45 deg. polariser in a common polarisation assembly, and then recombined and coherently superimposed. The 45 deg. angle refers to each polarisation. The relative phase shift is proportional to the electric field and thus to the applied voltage of the electric input signal. USE - For A/D conversion of RF modulated optical signals.