Non-Uniform-Digital-Analog Radio-Over-Fiber Scheme for Future Fronthaul Based on a Low-Complexity 4-Fold Symmetric Non-Uniform Quantization Method

We propose a non-uniform-digital-analog radio-over-fiber (NUDA-RoF) scheme based on a low-complexity 4-fold symmetric non-uniform quantization method and demonstrate it experimentally in a polarization-division-multiplexed (PDM) coherent transmission system. The 50-Gbaud PDM-NUDA-RoF signal with a net rate of 391 Gb/s/λ and a record single-channel common public radio interface equivalent data rate (CPRI-EDR) of 2 Tb/s/λ is successfully delivered in a 10-km standard single-mode fiber (SSMF) link. Results show that the NUDA-RoF scheme achieves a maximum signal-to-noise ratio (SNR) gain of ∼1.3 dB compared to digital-analog radio-over-fiber (DA-RoF) at an equivalent capacity. Significantly, the NUDA-RoF scheme demonstrates a ∼3.8-dB optical signal-to-noise ratio (OSNR) sensitivity improvement over DA-RoF at the 256-QAM error vector magnitude (EVM) threshold. The NUDA-RoF scheme has advantages over analog-radio-over-fiber (A-RoF) and DA-RoF in terms of SNR improvement, as well as advantages over digital- radio-over-fiber (D-RoF) in CPRI-EDR. Our work suggests many optimistic possibilities for the future radio access networks and mobile fronthaul.