Compact photonic chip assisted by multi-core fiber for radio beamsteering in 5G

This paper describes and evaluates experimentally a Si3N4 photonic chip based on optical ring resonators (ORRs) assisted by multi-core fiber (MCF) that enables radio beamsteering in 5G by the continuous tuning of the time delay applied to an antenna array. Each ORR includes two heaters: one for tuning the resonance wavelength and another to set the coupling coefficient. In this way, the configuration for beamsteering can be implemented by heater tuning or by wavelength shifting. Each optical path of the photonic chip comprises a thermally tunable optical side band filter (OSBF) and an ORR in cascade configuration. The output of each optical path is transmitted through a core of a MCF to distribute the modulated 5G signals to each array element at the transmitter antenna. This ensures that all the optical paths have the same length and enables the delay tuning of each array antenna element directly set from the photonic chip. Experimental demonstration is carried out with a four-core MCF with 26 GHz signals suitable for 5G transmission.