Ramon Maia Borges

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 photonic-assisted 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.

Reconfigurable Optical-Wireless Communications for Future Generations

This work reports a photonics-based convergent and reconfigurable optical-wireless network for future communications. The proposed architecture provides the functionality of frequency reconfiguration over different bands by using external modulation technique, which enables microwave frequency doubling. A proof of concept for LTE and Wi-Fi off-loading applications is presented. Experimental results demonstrate generation of low phase-noise and high spectral purity RF carriers at 2.6 and 5.2 GHz. Distortion absence has also been observed by applying radio over fiber technology to distribute the photonically-generated RF signals.

Development and Performance Analysis of a Photonics-Assisted RF Converter for 5G Applications

ABSTRACT This article presents a simple, ultra-wideband and tunable radiofrequency (RF) converter for 5G cellular networks. The proposed optoelectronic device performs broadband photonics-assisted upconversion and downconversion using a single optical modulator. Experimental results demonstrate RF conversion from DC to millimeter waves, including 28 and 38 GHz that are potential frequency bands for 5G applications. Narrow linewidth and low phase noise characteristics are observed in all generated RF carriers. An experimental digital performance analysis using different modulation schemes illustrates the applicability of the proposed photonics-based device in reconfigurable optical wireless communications.

Development and performance analysis of a photonic-assisted RF amplifier

This work contributes to the area of microwave photonics applied to telecommunication systems in two ways. Initially, a photonic-assisted RF amplifier is proposed and experimentally validated. It takes advantage of the Four-wave Mixing (FWM) optical nonlinear effect, ensured by launching two high optical power carriers into a highly nonlinear fiber. The RF gain is defined as the difference between the electrical power photodetected using a FWM product and that from the conventional RoF system at the same optical power level. Experimental results demonstrate 24 dB gain after photodetection of the first FWM product. Furthermore, a performance analysis based on numerical simulations is reported in order to propose a high capacity intensity modulated radio over fiber architecture for future broadband access optical-wireless networks. Bit-error-rate curves of a 10 Gbit/s NRZ signal in different conditions of optical signal to noise ratio (OSNR) are presented for illustrating the applicability of the proposed photonics-based RF device.

Photonics-based tunable and broadband radio frequency converter

Abstract. This paper is regarding the concept and development of a photonics-based tunable and broadband radio frequency converter (PBRC). It employs an external modulation technique to generate and reconfigure its output frequency, a digital circuit to manage the modulators’ bias voltages, and an optical interface for connecting it to optical-wireless networks based on radio-over-fiber technology. The proposed optoelectronic device performs photonics-based upconversion and downconversion as a function of the local oscillator frequency and modulators’ bias points. Experimental results demonstrate a radiofrequency (RF) carrier conversion with spectral purity over the frequency range from 750 MHz to 6.0 GHz, as well as the integration of the photonics-based converter with an optical backhaul based on a 1.5-km single-mode fiber from a geographically distributed optical network. Low phase noise and distortion absence illustrate its applicability for convergent and reconfigurable optical wireless communications. A potential application relies on the use of PBRC in convergent optical wireless networks to dynamically provide RF carriers as a function of the telecom operator demand and radio propagation environment.

Implementation of a photonics-based frequency reconfigurable optical-wireless network

This work reports the implementation of a frequency reconfigurable optical-wireless network based on a photonics technology. An optical modulator is used to dynamically manage and manipulate RF signals over different frequency bands by means of optical frequency multiplication. The proposed concept of a convergent and frequency reconfigurable architecture has been successfully demonstrated by applying radio over fiber technology in a geographically-distributed optical-wireless network. Experimental results of RF generation up to 10.4 GHz are presented, including high spectral purity RF carriers at 2.6 and 5.2 GHz with low phase noise and distortion absence.