Analysis of Radio over Fiber system for mitigating four-wave mixing effect

In this paper,an efficient 8-channel 32Gbps RoF(Radio over Fiber)system incorporating Bessel Filter(8/32 RoFBF)has been demonstrated to reduce the impact of non-linear transmission effects,specifically Four-Wave Mixing(FWM).The simulation results indicate that the proposed 8/32 RoF-BF system provides an optimum result w.r.t.channel spacing(75 GHz),input source power(0 dBm)and number of input channels(8).In comparison with the existing RoF system,the proposed 8/32 RoF-BF system has been validated analytically and it is found that the performance of the proposed system is in close proximity particularly in FWM sideband power reduction of the order of 4 dBm for the 8-channel 32Gbps RoF system.

Using Brillouin fiber-optic ring laser to provide base station with uplink optical carrier in a 10 GHz radio over fiber system

In this paper, a 10 GHz radio over fiber system is analyzed. The Brillouin fiber-optic ring laser is used in the center station （CS） to suppress the optical carrier for the modulation depth enhancement. Simultaneously, the Stockes wave induced by the Brillouin amplification injects and locks the Fabry-Perot （FP） laser to output a signal-mode optical source, which works as the uplink optical carrier.

PERFORMANCE IMPROVEMENT FOR A WCDMA RADIO OVER FIBER SYSTEM USING DIGITAL PRE-DISTORTER

In this paper,a Radio Over Fiber (ROF) system with a Digital Pre-Distorter (DPD) for WCDMA signal transmission is investigated.A Look-Up Table (LUT) based DPD and a Memory Polynomial (MP) DPD are applied in the ROF link so as to suppress the out-of-band spurious spectrum and improve the transmission performance.The experimental results show that the out-of-band emission due to existence of the third-order Inter-Modulation Distortion (IMD3) is obviously sup-pressed by these two DPD.An Adjacent Channel Power Ratio (ACPR) improvement of 8 dB is ob-tained for a single-carrier WCDMA signal transmission.These two DPD have equal ability in lin-earization of the ROF system for a three-carrier WCDMA signal transmission.There is no apparent memory effects exist in the ROF link.

Adaptive Performance Improvement of Fiber Bragg Grating in Radio over Fiber System

The combination of Radio Frequency and Optical Fiber has resulted high capacity transmission at lower costs components and makes Radio over Fiber as a current trend of large broadband communication. In Fiber optics field, the use of Fiber Bragg Grating (FBG) was been proposed in recent research with different purpose of uses. However, the compensation of dispersion method of Fiber Bragg Grating (FBG) can boost significantly the system performance. This paper investigates the performance capacity improvement of adaptive Radio over Fiber system. The system design was performed using OptiSystem 7.0 software, which 10 Gb/s Non Return to Zero (NRZ) signal was launched into 50 Km Universal Mode Fiber and Fiber Bragg Grating was used as a compensator of dispersion before frequency up conversion. Therefore, the system performances were investigated by comparing the Bit Error Rate (BER) and Q-factors of Positive Intrinsic Negative (PIN) and Ultrafast Avalanche Photodiode (APD) as optical receivers. The Eye diagram analyzer showed acceptable improvement due to use of Fiber Bragg Grating as a compensator of dispersion.

Performance Analysis of WLAN Medium Access Control Protocols in Simulcast Radio-Over-Fiber-Based Distributed Antenna Systems

The performance of three wireless local-area network(WLAN) media access control(MAC) protocols is investigated and compared in the context of simulcast radioover-fiber-based distributed antenna systems(RoF-DASs) where multiple remote antenna units(RAUs) are connected to one access point(AP) with different-length fiber links.The three WLAN MAC protocols under investigation are distributed coordination function(DCF) in basic access mode,DCF in request/clear to send(RTS/CTS) exchange mode,and point coordination function(PCF).In the analysis,the inter-RAU hidden nodes problems and fiber-length difference effect are both taken into account.Results show that adaptive PCF mechanism has better throughput performances than the other two DCF modes,especially when the inserted fiber length is short.

Transmission Restriction and Suppression of Radio over Fiber Communication System

This article puts forward long-reach and high-performance Radio over Fiber (RoF) Communication Systems.Two schemes are proposed for solving the transmission restriction factors of the RoF system and verifies the system through experiments.One scheme is 40GHz RoF system based on external modulation with odd-order sideband-suppressed.The other one is 40GHz Optical Frequency Division Multiplexing (OFDM) system based on Optical Carrier-Suppression (OCS),external modulation.Both theory and experiment prove that the two systems allow not only low chromatic dispersion,but also long-distance transmission.

通过光电相位调制和光纤光栅滤波实现Radio over Fiber传输系统设计

提出并模拟证明了基于电光相位调制(PM)和布拉格光纤光栅(FBG)实现受抑光载波的双边带(DSBOCS,Double-Sideband with Optical Carrier Suppression)的双向Radio over Fiber(RoF)传输系统网络设计方案.激光光源置于中心站,载有信息的光信号通过光纤到达基站后经FBG分成两路,其中一路是被接收的下行信号,另一路作为上行信号调制后返回中心站.通过FBG,其下行信号不但实现了受抑光载波的双边带———使通信带宽加倍,上行信号作为光源通过电光强度调制,有效地实现信息的上载.仿真结果表明,光源发射功率为3 dBm,无光放大,在色散系数为20 ps/(nm.km),衰减系数为0.25 dB/km的单模光纤中传输,超高频RF信号的频率可达24 GHz,系统码元传输速率可达2.5 Gbit/s、传输距离50 km以上.

Impairments Approximations in Assembled mmWave and Radio Over Fiber Network

The fiber nonlinearity and phase noise(PN)are the focused impairments in the optical communication system,induced by high-capacity transmission and high laser input power.The channels include high-capacity transmissions that cannot be achieved at the end side without aliasing because of fiber nonlinearity and PN impairments.Thus,addressing of these distortions is the basic objective for the 5G mobile network.In this paper,the fiber nonlinearity and PN are investigated using the assembled methodology of millimeter-wave and radio over fiber(mmWave-RoF).The analytical model is designed in terms of outage probability for the proposed mmWave-RoF system.The performance of mmWave-RoF against fiber nonlinearity and PN is studied for input power,output power and length using peak to average power ratio(PAPR)and bit error rate(BER)measuring parameters.The simulation outcomes present that the impacts of fiber nonlinearity and PNcan be balanced for a huge capacity mmWave-RoF model applying input power carefully.

Application of Remote Radio Head over Fiber Technology

The Remote Radio Head (RRH) over Fiber system is a new distributed network coverage mode.It processes the baseband parts concentratively by separating the baseband and Radio Frequency (RF).It moves the RF modules using fibers from the Base Stations (BSs) to the remote RF units.These RF modules are placed on the stations to be covered.This solution saves many equipment rooms required by conventional solutions.Meanwhile,it supports RRH over a large number of fibers through high-capacity macro BSs to realize the conversion between capacity and coverage.In addition,the RRH system also supports the coverage in other situations,such as high-speed railways and ultra-long distance.It is one of the most widely used technologies in the 3G network.

面向FTTR的低成本半双工模式收发机方案及关键技术

为了降低光纤到房间系统中光网络单元的数量和成本,提出了半双工模式收发机方案。该方案通过模式切换开关连通不同电路组件,实现通信系统的收发功能。同时,将该收发机与Wi Fi无线收发系统配合使用,形成了“光纤-无线”半双工收发系统架构,实现光信号和射频信号在光纤到房间系统中的传输。测试结果表明,设计的模式切换开关与收发机协同工作顺畅,在数据传输速率为5 Gb/s时,接收端信号眼图清晰,验证了半双工模式收发机方案的可行性。

基于Optisystem的微波光纤通信系统仿真与性能分析

针对微波光纤通信系统,在对其原理分析和功能结构设计的基础上,利用Optisystem光通信系统仿真软件,搭建了一个基于Optisystem的微波光纤通信系统仿真平台,通过设定系统参数,得出仿真结果并进行了分析,验证了系统设计方案的可行性和正确性,从而为将来的实际应用提供理论依据。

5G光载无线通信前传系统数字预失真线性化研究

第五代移动通信系统新空口(5G NR)的信号带宽、调制度和峰均比相比4G信号高很多。用于小蜂窝或微蜂窝基站组网的光载无线通信(Radio-over-Fiber,RoF)前传系统的非线性失真也更加严重。为了使5G NR信号线性传输,采用记忆多项式(Memory Polynomial,MP)和广义记忆多项式(Generalized Memory Polynomial,GMP)模型构建数字预失真器,矫正5G RoF前传系统的非线性。在实验中搭建了2 km光纤的RoF前传系统,并采用100 MHz带宽5G NR信号作为测试信号对其进行线性化测试。实验结果表明,采用MP和GMP数字预失真器进行线性化时,5G RoF前传系统的邻信道功率比(Adjacent Channel Power Ratio,ACPR)可分别改善13 dB和17 dB以上。这说明MP和GMP数字预失真器对5G RoF前传系统的非线性具有显著的抑制作用。因此基于MP和GMP两个模型的数字预失真器均可用于5G RoF前传系统的线性化,而且GMP预失真器比MP预失真器对该系统线性化的能力更强。

Broadband V-band Radio over Fiber Uplink Fronthaul Transmission Using Cascaded Microwave Photonic Downconversion Topology

Exploiting microwave photonic(MWP)techniques to generate and distribute high-frequency millimeter-wave(mm-wave)signals,termed mm-wave radio over fiber(m-RoF)signals,holds considerable potential for achieving highdensity and high-capacity fifth-generation and beyond networks.Herein,we experimentally validate a broadband m-RoF uplink fronthaul transmission system using the MWP downconversion concept,which comprises receiving and processing radio-frequency(RF)signals in the unlicensed V-band at around 60 GHz.The proposed system harnesses the simple cascaded modulator topology,in which an ultrawideband off-the-shelf Mach–Zehnder modulator(MZM)renders a simplestructured remote radio head by directly encoding the broadband 60 GHz uplink RF signal into the optical carrier.The nonlinear transfer function of another MZM at the center unit is explored to achieve subharmonic downconversion using cost-effective low-frequency local oscillator signals.Based on proof-of-concept experiments,mm-wave four quadrature amplitude modulation orthogonal frequency-division multiplexing signals centered at frequencies ranging from 51 GHz to 70 GHz are successfully downconverted into signals at the intermediate frequency(IF)of 1.4 GHz.In the case of 1.2 m mm-wave,free-space,and 5 km m-RoF transmissions,the obtained IF signals with a total bandwidth of 2.4 GHz achieve a bit-to-error ratio performance lower than the 7%hard-decision forward error correction limit of 3.8×10^(−3).A gross bit rate of 10 Gbit/s can be achieved over a total spectrum of up to 10 GHz,which fully covers the globally unlicensed V-band of 57-66 GHz.

Generation and transmission RZ-OOK signal for of dispersion tolerant lO-Gbps radio over fiber link

We proposed and demonstrated the generation and transmission of 10-Gbps retum-to-zero ON/OFF keying （RZ-OOK） signal using a new technique without pulse carving at transmitter. The new technique is characterized by a 3 dB built-in gain with better tolerance for chromatic dispersion in standard single mode fiber （SSMF）. Fiber Bragg grating （FBG） is used as chromatic dispersion compensating device to investigate the toler- ance of the proposed scheme. The simulation model of wavelength division multiplexing （WDM） based on OptiSystem.v.8.0 is presented. Simulation results show that there are error free transmission performance in a distance of 600 km with negligible power penalty and improved receiver sensitivity compared to conventional pulse carving approach.

相位偏移和分束比对八倍频光毫米波产生及传输的影响分析

相位偏移和分束比极大地影响了产生光毫米波信号的边带抑制比以及光纤无线(ROF)系统的BER。针对串联两个马赫-曾德尔调制器产生八倍频光毫米波信号的方案,利用贝塞耳级数展开的方法,推导了相位偏移和分束比影响下,光毫米波信号的严格通用解析解,当分束比偏离0.001,相位偏移1°时,边带抑制比可达35.9 dB,能够忽略谐波分量的影响。仿真结果表明,在BER=10-10的条件下,当八倍频光毫米波信号背靠背传输时,分束比偏离0.001和相位偏移1°的功率代价仅为0.001dB,经20 km标准单模光纤传输后的功率代价为0.145 dB,系统性能良好。

多路射频信号的光纤无线系统调制器偏置点优化

马赫-曾德尔调制器的直流偏置工作点直接影响光纤无线链路的性能。在考虑三路射频信号输入的条件下,建立了基于单驱动马赫-曾德尔调制器的光纤无线链路模型,分析了调制器偏置点对链路射频增益、噪声系数以及动态范围的影响。仿真结果表明,在调制器直流偏置相移为0.32π时,射频增益达到最大、噪声系数达到最小、动态范围达到最大,此时光纤无线系统性能最优。

MZI产生光载毫米波的ROF系统

提出一种采用马赫增德尔干涉仪(MZI)产生光载毫米波的光纤无线通信(ROF)系统。该系统采用基带信号与本振信号的混频信号驱动光相位调制器,以产生多边带光信号,用MZI将多边带光信号的重复频率增至2倍。建立了产生光载毫米波的理论模型,并通过仿真试验验证了系统的可行性。结果表明:用40 GHz光载毫米波调制2.5 Gbit/s基带信号,经60 km光纤传输后,眼图清晰可见,功率代价为4.2 dB。

光载无线通信链路拉格朗日乘子线性度优化

非线性失真是影响光载无线通信链路无杂散动态范围和工作带宽的主要因素.通过结合射频功率比、偏振复用和偏置控制技术,针对分布式天线系统,构建了一种大动态范围和跨倍频程带宽多通道光载无线通信链路.利用拉格朗日乘子法对所提链路进行线性度优化建模,得到了射频输出功率、偏振入射角和射频功率比之间的最佳折衷,从而在抑制三阶交调失真和二阶谐波失真的基础上,实现了链路线性度的最优化.仿真和实验结果验证了所提方案的有效性和可行性.

多信道数字与模拟RoF系统性能比较

综合比较多信道数字RoF和模拟RoF的传输系统方案和性能,并分析数字RoF如何利用带通采样的特点实现只需要用ADC和DAC就可以完成频率迁移。推导和分析多信道模拟RoF与数字RoF受到的非线性影响,并通过Optisystem进行仿真。理论和仿真都证明DRoF链路比模拟RoF链路有着更好的SNR性能和动态范围,更适合远距离传输。

采用半导体光放大器进行直接调制的全双工光纤无线通信系统实验研究

提出并实验研究了一种将光源和光调制器集中于中心站,而基站中使用直接调制半导体光放大器的新型光纤无线通信系统,在中心站采用相位调制器和光交错复用器产生光毫米波,并同时将未调制信号的光载波与光毫米波一起发送到基站;在基站中将下行链路的光载波分离出来作为上行链路的光载波,并利用半导体光放大器将上行链路的信号调制到光载波上,同时对上行链路的信号进行放大。实验结果显示可以将下行链路中2.5Gbit/s的数据和上行链路中250Mbit/s的数据在单模光纤中传输40km。