N. Mohamed

Review on system architectures for the millimeter-wave generation techniques for RoF communication link

Generation of millimeter-wave (mm-wave) signal for radio over fiber (RoF) currently being investigated and studied by many researchers due to the demand of the mm-wave band for future communication system mostly in wireless local area networks (WLANs) applications. RoF is a system where high microwave frequency signals are delivered through optical fiber between the central station (CS) and the base stations (BSs). The use of optical fiber for signal distribution in mm-wave radio communication systems has been widely investigated, since they provide high bandwidths and small cell sizes (picocell). They also offer the potential for the low cost infrastructure needed to develop broadband mobile services. This paper will explain the whole picture of RoF technology followed by RoF link configurations where radio frequency (RF) signal can be transmitted directly over fiber either at the RF or intermediate frequency (IF) signals. The review mainly focuses on the mm-wave generation techniques for radio over fiber including: optical heterodyning, external modulation, optical transceiver, and up- and down-conversion.

HBT Optoelectronic Mixer Design for Radio over Fiber System

Radio over fiber (RoF) system is the solution for the providing highly reliable communication service. This system is characterized by having both a fiber optic link and free-space radio path to exploit the synergy of two complementary technologies; the broadband mobile wireless access and fixed optical access. Optoelectronic mixing is required in RoF systems to detect the RF modulated optical signal and perform frequency up-conversion. In this work, three-terminal InP/InGaAs HBT with optical access has been used as the optoelectronic mixer (OEM) for front-end RoF optical receiver configuration. Thus in this configuration, the photodetection and frequency conversion can be achieved in p-i-n photodiode and HBT device, which considerably simplify the conventional method. The RoF OEM was successfully simulated using a nonlinear microwave simulator to perform harmonics balance analysis, which represented actual photodetection model and nonlinear dynamic optoelectronic mixing behavior. In this paper we reported the - 5.2 dB maximum internal mixing efficiency for 400 MHz IF modulated signal to 3.4 GHz upconverted RF signal with LO power is -2dBm, and that agreed with conventional theoretical analysis. In this article, the theory of operation, the device structure of the RoF OEM and its characteristic will be presented.

Millimeter-Wave Carrier Generation System for Radio over Fiber

Due to the huge demand for the mm-wave band in future communication system applications, many researchers are investigating and continue working on the generation of millimeter-wave (mm-wave) signal for radio over fiber (RoF). RoF is an expanding technology that applicable in high channel capacity, wider service coverage and broadband mm-wave access system. However, the limited availability of the RF bands require utilization of the mm-wave frequency bands to meet the obligation for higher signal bandwidth and overcome the frequency congestion in the future RoF-based optical-wireless access networks. Broadband wireless communication has introduced great interest in mm-wave bands due to its wide transmission bandwidth and also the opportunity of frequency reuse. This paper mainly focuses on the mm-wave carrier generation techniques for radio over fiber including: optical heterodyning, external modulation, optical transceiver, and up- and down-conversion.

Optical front-end receiver configuration for 30 GHz millimeter-wave signal Radio over Fiber system

Radio over fiber (RoF) technology is proposed solution for the reducing cost and providing highly reliable communication services. The system is very cost-effective solution by localization of signal processing in central station and also uses a simple base station. In this paper, two configurations of RoF system were presented. First, the intermediate frequency (IF) frequencies are upconverted to radio frequency (RF) at the central station and the RF are transmitted over single mode fiber directly at the radio carrier frequency. In the second configuration, the IF are transmitted over single mode fiber and converted to the original RF at the optical receiver. This report is focusing on the RoF optical frontend receiver configuration at the base station or also known as optical heterodyne receiver that employing an optoelectronic mixer. In this configuration, the receiver is performing photodetection and frequency conversion simultaneously. Thorough review and comparison of the previous works on the optoelectronic mixer and frequency conversion for up to millimeter-wave band will presented. Finally, the theoretical analysis and the harmonic balance modeling of the proposed optical front-end receiver and frequency up conversion system will be discussed.

Photonic up-conversion frequency utilizing harmonic balance simulation analysis

This paper reveals a model of an optical front-end receiver with an intermediate frequency (IF) signal transmission utilizing photonic up-conversion technique through harmonic balance simulation analysis. This technique is proposed at base station (BS) merited by the dispersion effect that occurs on the fiber at higher frequency signals. Heterojunction bipolar transistor (HBT) is modeled as an optoelectronic mixer (OEM) due to the nonlinearities of HBT to attain the up-conversion signal. IF modulated input signal is in the range of 0.1 GHz to 0.4 GHz and the local oscillation (LO) frequency of 30 GHz is pumped to the base terminal with input power of −10 dBm. 30.4 GHz up-converted frequency with about −2.32 dBm of conversion gain is obtained at VBE = 0.76 V based on simulation study.

Performance characterization of an optoelectronic mixer (OEM) model based on nonlinear InP/InGaAs heterojunction bipolar transistor

We model an optical front-end receiver with an intermediate frequency (IF) signal transmission utilizing photonic up-conversion technique through harmonic balance simulation analysis. A mixing model is carried out taking advantages of the nonlinearities of the InP/InGaAs HBT to achieve up-conversion of a modulated optical signal. The intensity of the optical signal is modulated by an IF signal ranging from 0.1 GHz to 0.4 GHz and the local oscillation frequency injected into the base terminal is 30 GHz with an input power of −6 dBm. The nonlinear, harmonic balance technique is employed to simulate the mixing performance of the InP/InGaAs HBT OEM. 30.4 GHz up-converted frequency at collector-emitter voltage, VCE = 1.6 V was achieved at the output port based on simulation study.

Nonlinear analysis for performance characterization of heterojunction bipolar transistor optoelectronic mixer

A nonlinear, harmonic balance technique is employed to simulate the mixing performance of the HBT optoelectronic mixer (OEM) model. 30.4 GHz up-converted frequency at VCE = 1.6 V was achieved at the output port based on simulation study.

Experimental demonstration of a downlink remote optical local oscillator for radio over fiber system

A downlink remote optical local oscillator for radio over fiber (RoF-ROLO) system was successfully demonstrated experimentally at up-conversion frequency of 12.92 GHz. Up-conversion architecture was employed at the base station (BS) while the optical signal was generated at the central station (CS) using stimulated Brillouin scattering (SBS) technique at frequency of 10 GHz with 25 km of SBS fiber loop length. The optically generated signal was deployed as a remote local oscillator (LO) signal of a mixer at the BS. RoF-ROLO system was specifically designed to achieve the key specifications which are lower input power level, high system conversion gain as well as minimizing the dispersion effect. In this study, about -9.22 dB and -6.99 dB of the system conversion gain have been obtained through the simulation and experimental demonstration respectively at optical carrier input power of 1 dBm.