Investigation of Optical Modulators in Optimized Nonlinear Compensated LTE RoF System

Abstract

This document may differ from the final, published version of the research and has been made available online in accordance with publisher policies. To read and/or cite from the published version of the research, please visit the publisher's website (a subscription may be required.)IEEE/OSA Journal of Lightwave Technology 1  Abstract-In this paper, we investigate a nonlinear compensation technique with two different architectures using direct modulation (DM) and external modulation (EM) techniques, termed as DM based frequency dithering (DMFD) and EM based frequency dithering (EMFD). We show that DMFD and EMFD methods operate substantially different in radio-over-fiber (RoF) system by optimizing the dithering technique relative to the LTE technology. The proposed techniques is only applicable if the condition of {f L < f d < f RF } is met, where f L represents the dithering boundary limit of 14 MHz, f d is DMFD signal frequency and f RF is the RoF carrier frequency. Analysis of the optical launch power for DMFD and EMFD methods reveal that the stimulated Brillouin scattering (SBS) threshold is above ~6 dBm for the LTE-RoF system. In addition, we also unveil that DMFD and EMFD methods do not introduce additional distortion for the linear and optimum optical launch power regions, which are frequency chirp driven regions. If the given condition is met, the proposed method improves the LTERoF system without any shortcoming. Finally, at 10 dBm launch power, DMFD and EMFD methods exhibits an average signal-tonoise ratio (SNR) gain of ~5.95 dB and ~7.71 dB, respectively. Index Terms-Long Term Evolution (LTE); Radio-over-fiber (RoF); Nonlinear Compensation; Optical OFDM (OOFDM) I. INTRODUCTIONThe actively growing end user subscriptions with bandwidth hungry, high specification, real-time, and delay-sensitive applications have been driving the mobile communications technology to continuously progress forward. The 3 rd generation partnership program (3GPP) established a standard known as the LTE to support the rapidly evolving mobile communication requirements [1].In the radio access network of LTE, eNodeB (eNB) functions as the base station (BS) similar to the global system Manuscript received April 29, 2013 for mobile communications (GSM) and universal mobile telecommunication system (UMTS) BSs. However, the eNB provides the real-time operation via a 2-node architecture, without an external central controller. The 2-node architecture is achievable because the eNB architecture is designed with built-in central controller with a radio access network, and such evolution leads to costly infrastructure expansion. In addition, the vastly allocated spectrums for LTE in urban locations throughout the world are either 2.6 GHz or 1.8 GHz [2] where the drawback is the excessive loss on the wireless propagation. As a result the eNB cell radius is limited to 1 km in urban operating conditions [3]. The throughput for the user equipment (UE) at the cell edge is <20 Mb/s from the maximum of 100 Mb/s owing to the deteriorating SNR, thu...

A Novel Scheme for Orthogonal Frequency Division Multiplexing-Radio over Fiber Based on Modulator and Dithering Technique: Impact of Self Phase Modulation and Group Velocity Dispersion

“…Investigated Direct Modulation (DM) and External Modulation (EM), and direct modulator on QAM (Quadrature Amplitude Modulation) has exhibits to mitigate SBS (stimulated Brillouin scattering) and optimization nonlinear compensated for LTE (Long Term Evolution)-RoF with varied launch power for enhanced power budget [3]. Another line of research is aimed to demonstrate of the nonlinear compensation LTE-RoF based on DMFD (Direct Modulation Frequency Dithering) and EMFD (External Modulation Frequency Dithering) also to mitigate SBS including analysis of QPSK (Quadrature Phase Sift Keying), 16 QAM, and 64 QAM scheme [4]. On the other hand, was investigated to optimized launch power for the [5].…”

Dithering Analysis in an Orthogonal Frequency Division Multiplexing-Radio over Fiber Link

“…Compensated nonlinear on RoF also observes in another paper to achieve high power budget using power gain. The other project proposes to investigate performance and characteristic OFDM based on modulation for Rolf [1], [3], [4]. A modeling system to achieve high performance based on OFDM optical network and introduce a novel ICI (Inter Carrier Interference) reduction algorithms cancellation under the various channel environments has already been considered in the literature [5], [6].…”

Spectral Shape Impact of Nonlinear Compensator Signal in LTE RoF System

“…The principle of operation is based on simple amplifying and forwarding RNs with RoF acting as the interface between the eNB and RN [4][5][6][7][8]. In other words, instead of eNB, the RN delivers the LTE signal to the UE at the cell edge.…”

“…As a solution, we recently proposed a direct modulation based frequency dithering (DMFD) method for nonlinear compensation specifically designed for the LTE RoF system [5], which enabled the use of higher optical launch powers. Further optimizations of this method were carried out in the perspective of optical modulators [6] and dithering frequency f d with higher order modulations [7]. In [6], it is shown that DMFD method introduces an additional ~3 dB optical power penalty in comparison to external modulation while imposing a lower cost.…”

“…In [6], it is shown that DMFD method introduces an additional ~3 dB optical power penalty in comparison to external modulation while imposing a lower cost. It is also shown in [7] that f d has to meet the condition of {f L < f d < f RF }, where f L and f RF are the dithering boundary limit and the LTE carrier frequency, respectively. Ref.…”