Experimental Demonstration of Multi-channel Frequency Quadrupling for Analog Optical Fronthauling

This paper experimentally demonstrates multichannel frequency quadrupling for analog radio-over-fiber for fronthauling multi-sector antennas in the mmWave wireless systems and beyond. We employ dual parallel Mach-Zehnder modulators to modulate intermediate frequency signals carrying data as per 5G specifications, with up to 256 QAM modulation in dense wavelength division multiplexed channels, followed by a single multiplier modulator at the base band unit to upconvert all the channels to 26.4 GHz at the remote radio head location. We show that the optical quadrupler scheme complies with the error vector magnitude limits as specified by 3GPP for up to 256 QAM modulation over 2 km fiber in the multi-channel scenario in both double side band and single sideband implementations. We demonstrate the tunability of our scheme by generating RF across the n258 band (24.25 - 27.5 GHz). The proposed scheme offers a cost-effective, scalable solution for analog radio-over-fiber fronthauling for multi-sector antenna deployments.