This paper reports and analyses the hybrid 5G NR (new-radio) fronthaul technology with emphasis in the different functional splitting points, and the associated silicon-photonics technologies which enable a completely integrated electro-optical transceiver. Different silicon photonics solutions have been proposed so far targeting an integrated solution combining electronics and photonics, where electronics deal with digital coding and MAC forming, and photonics implement modulation (enabling QPSK, QAM and PAM4 transmissions above 100 Gbit/s) and switching functionalities (reducing the switching time to the ns range). High-speed transceivers integrated in bulk CMOS would enable Tbit/s optical interconnects. In particular, this work firstly summarizes the recent advances and challenges of silicon photonics technology that will have an impact on 5G applications in a near future. Next, an experimental demonstration of a radio-over-fiber fronthaul for the simultaneous provision of multiple radio-access technologies including 2G, 3G and 4G is included. Enhanced capabilities enabled by silicon photonics including MIMO and beamforming are also evaluated.
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