Ultra-broadband photonics-based RF front-end toward 5G networks

We propose the concept and report the development of an ultra-broadband photonics-based RF front-end, as well as its experimental digital performance analysis up to 38 GHz. The proposed RF front-end applies optical frequency multiplication based on the external modulation technique and the optical nonlinear effect four-wave mixing for enabling a combination of photonicassisted RF upconversion and amplification, regardless of frequency operation. We present ultra-broadband operation and frequency tunability from DC to 38 GHz by simultaneously performing RF conversion and amplification in the optical domain. The experimental results of a successful implementation in a real wireless-optical network demonstrate the RF front-end applicability in the three potential frequency bands for 5G networks, namely, 6.0, 28, and 38 GHz. Furthermore, a detailed digital performance investigation using different modulation formats is presented based on diverse RF and optical parameters, including signal-to-noise ratio, RF gain, and error vector magnitude. Low phase noise, spectral purity, and distortion absence are also observed for all frequency bands.