Mitigation of atmospheric losses of satellite-to-ground laser links using coherent detection

In satellite-to-ground free-space optical communications, a major challenge is the atmospheric transmission. Coherent detection is currently the preferred solution over direct detection because it allows the use of phase modulations, resulting in better energy and spectral efficiency. The CALICO project (Compensation of Atmospheric Losses in Satellite-to-Ground Laser Link with Coherent Detection) aims to design a coherent receiver capable of performing homodyne demodulation of a QPSK signal in the presence of significant Doppler effect. The processing performed should reduce the need for control or error correction, thereby helping to increase the useful data rate.