Multi-core Fiber Technology supporting MIMO and Photonic Beamforming in 5G Multi-Antenna Systems : (Invited paper)

This paper describes and experimentally validates different multi-antenna system applications supported by a multicore fiber (MCF) optical fronthaul. The MCF fronthaul enables the simultaneous transmission of different optical data streams at the same wavelength by the spatial multiplexing of multiple-input multiple-output (MIMO) signals. In addition, the MCF enables simultaneous radio beamforming by transmitting the same optical data signal with different phase or time delays to each antenna element. Both MIMO and beamforming capabilities are required for 5G multi-antenna systems. Experimental demonstrations of $4 \times 4$ MIMO transmission and multi-beam $4 \times 1$ beamforming using a commercially available 4-core fiber are reported in this work. Optical beam-steering in 5G is achieved using a Si
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photonic chip based on optical ring resonators (ORRs) that enables the continuous and centralized tuning of the time delay applied to each antenna element.