Linearized Full Duplex Radio-Over-Fiber-Over-Space Mixerless Transceiver Architecture

This paper proposes a full-duplex Radio-over-Fiber-over-Space (RoFoS) transceiver's architecture with mixerless frequency conversions. The polarization splitting of the optical carrier into two orthogonal polarizations provides away to carry both downlink (DL) and uplink (UL) optical signals in one optical channel. In this work, the UL and DL signals are chosen to provide proof-of-implementation for the 5G fronthaul networks. In the baseband unit (BBU), the DL signal at the intermediate frequency (IF) 2 GHz is sent through RoFoS to the remote radio head (RRH) and broadcasted at 19 GHz, without the need for any mixing stage. In the UL path, at the RRH, the UL signal with an interferer (I) and added noise are received at 4 GHz then optically modulated and sent through the same optical channel to the BBU to be compensated for any distortion or hardware impairments. Digital compensation polynomial based models are used to reduce the distortion generated from the optical, electrical, and electro-optical components in the RoFoS transceiver. The error vector magnitude (EVM) and the signal to noise ratio (SNR) are calculated and compared to the 5G/NR standards test requirements.