Phase Modulation-based Fronthaul Network for 5G mmWave FR-2 Signal Transmission over Hybrid Links

In this paper, we experimentally demonstrate the feasibility of a phase modulation (PM)-based analog optical mobile fronthaul network for seamless millimeter wave (mmWave) signal transmission over hybrid standard single-mode fiber (SSMF), free space optics (FSO) and radio links. As a proof of concept, a 64-QAM LTE signal has been transmitted over 25 GHz in a 10 km SSMF, 2 m FSO and 1 m radio link without the need for optical amplifiers. After fiber propagation, non-significant signal degradation has been obtained over the wireless links, with an estimated sensitivity level of received electrical power -45.8 dBm. Despite the advantages of PM-based approaches, the use of optical filtering in our system provides easy scalability by including dense wavelength division multiplexing (DWDM) schemes. Also, the comparison with direct intensity modulation (IM)-based approach allows to assess PM-approach as a promising solution for seamless mm Wave signal transmission over future networks.