Free-Space Optical Communication Using an Optical Frequency Comb and Modulating Retroreflectors

The paper presents a high data rate optical communicationmethod with a swarm of unmanned aerial vehicles(UAVs) by combining quantum-well modulating retroreflectors(MRRs) and an optical frequency comb.The passive optical link between a laser station and UAVsusing MRRs can reduce the mission complexity and powerconsumption at UAV sites. While increasing the laser power is astraightforward way to further decrease power consumption atUAV sites, the saturation power of the photodetector (PD) at thelaser station site can set the lower limit of power consumptionsince one PD has to receive all lights from UAVs.We used multiple comb modes as independent data transfercarriers. We designed a simple optical system consisting of aquantum-well modulator (QWM), a diffraction grating, a lens,and a planar focal plane. We experimentally realized thataround 100 modes can be used with a near-diffraction limit.Our simulation showed that using a comb can reduce powerconsumption at UAV sites compared to using a continuous-wave(CW) laser with some specific conditions. One of the applicationsof this method is a distributed interferometric antenna thatobserves the frequency range from radio frequencies to a fewtens of GHz.