Clock and Carrier Synchronized Multi-Band Wireless Communications Enabled by Frequency Comb Dissemination in Radio Access Networks

Next-generation radio access network (RAN) requires wireless communication in multiple frequency bands between distributed unit (DU) and the radio unit (RU) for optimum spectrum usage and increasing data capacity. Besides, accuracy positioning and low latency applications such as autonomous vehicles have motivated clock distribution in RAN. An approach to simultaneously achieve clock and multi-band carrier synchronisation is to send an optical frequency comb from DUs to RUs. Here we demonstrate a multi-band 16QAM wireless transmission using synchronised carriers at 12.5, 25 and 37.5GHz. This achieves low noise RF carrier distribution over 22km standard single mode fiber (SSMF) with 70-fs root-mean-squared (rms) jitter, crucial for high order modulation format. We also modelled the impact of the fiber chromatic dispersion on the power fading of the comb transmitted RF carriers, based on which we show an optical spectrum shaping method to mitigate power fading of the detected multi-carriers. Finally, we experimentally study the impact of fiber dispersion and phase noise of the comb on the phase noise of the distributed RF carriers.