Fading-Free 5G New Radio mm-Waves Generation Using Photonic Integrated Frequency Combs.

We experimentally demonstrate the use of an integrated optical frequency comb (OFC) for remotely generating low-phase noise millimeter-waves (mm-waves) carriers. The Indium Phosphide (InP) device is composed of phase modulators in tandem and is configurable in OFC center frequency and tone spacing. The device is applied in a centralized radio access network (C-RAN) architecture and the realized OFC is transported over 12.5 km of a conventional single-mode fiber (SMF) link aiming to remotely generate mm-waves. The impairments induced by the chromatic dispersion (CD) on the photodetected electrical carriers are evaluated, i.e., the periodic RF power fluctuations based on the electrical frequency and the SMF length. Experimental results demonstrate that, by properly managing the phase modulator bias and the phase delay supplied to the PIC, the impact of CD on the electrical carriers can be significantly reduced, leading the optical frequency comb to sum up in-phase after the photodetection process. The OFC-based and remotely generated carrier at 28 GHz is used to up-convert a 100 MHz 5G new radio (NR) signal, demonstrating suitable root mean square error vector magnitude (EVMRMS) performance. Indeed, the OFC-based 5G NR signals met the 3GPP requirements with margins up to 7.7%, which enables the 5G wireless link at 28 GHz. Therefore, the proposed system is able to remotely generate mm-waves signal while minimizing the fading impact on the electrical signals, allowing to replace high-frequency up-converters at the remote 5G radio units.