Hybrid Free-Space Optical / cmWave Transmission over Shared Antenna Aperture

Hybrid signal transmission over both free-space optics (FSO) and radio-frequency (RF) carriers can highly benefit from compact air interfaces when adopting shared-aperture antenna concepts. Towards that, we evaluated lensed horn antennas as consolidated air interface compatible with FSO and FR3-band transmission. To simplify the remote radio head further, the joint air interface is paired with mode-selective signal coding and optical modulation to yield noise-robust radio signal transmission in the FSO mode while reaping the benefits of photonic up-conversion to the FR3 band in the RF mode. Evaluation of the hybrid FSO/FR3 transmission over shared antenna aperture yields error vector magnitudes of 5.9% and 9.4% for radio signal transmission in FSO and FR3-band modes over an end-to-end link configuration that involves a fronthauled remote radio head with a compatible optical budget of up to 19 dB, a wireless trunk link for signal relay to a distribution node and local wireless access.