Turbulence mitigation in a 28 GHz radio‐over‐free‐space optics link using an integrated Mach–Zehnder interferometer and a diversity combining receiver

Abstract

We propose an integrated Mach-Zehnder interferometer and diversity combining receiver (MZI-DC Rx) to mitigate the atmospheric turbulence-induced fading in millimetre-wave (MMW) radio-over-free-space optics (RoFSO) links. We have used a carrier frequency of 28 GHz as recommended for the fifth-generation wireless access networks and considered two optical MMW signal generation schemes namely double-and single-sidebands. In direct detection (DD)based RoFSO, the link performance is limited by atmospheric turbulence. We show that, the proposed Rx can overcome this detrimental effect. It is verified by investigating the transmission of a 10 Gb/s 16-quadrature amplitude modulation signal at 28 GHz over a 1 km FSO channel under weak and strong turbulence regimes. For DSB-based MMW, the proposed Rx offers improved error vector magnitudes of about 0.8% and 5.7% and modulation error ratios of 1.3 and 4.9 dB under weak and strong turbulence regimes, respectively compared with the DD Rx. For the SSB scenario under weak turbulence, the proposed Rx achieves 4 dB improvement in receiver sensitivity and four orders of magnitude enhancement in the bit error rate over the DD Rx. The proposed Rx can be integrated on a single chip for further cost reduction.