Low Complexity Digital Pre-Distortion (DPD) for Multi-Band Radio over Fiber Transmission Systems

Nonlinear distortion is one of key limiting factors in radio over fiber (RoF) transmission systems. To suppress the nonlinear distortion, digital pre-distortion (DPD) has been investigated considerably. However, for multi-band signals, DPD becomes very complex, which limits the applications. To reduce the complexity, many simplified DPDs have been proposed. In this work, a new multidimensional DPD is proposed, in which in-band and out-of-band distortion are separated and the out-of-band distortion is evaluated by sum and differences of all input signals instead of all individual input signals, thus complexity is reduced. An up to 6-band 64-QAM orthogonal frequency division multiplexing (OFDM) signal with each bandwidth of 200 MHz in simulations and a 5-band 20 MHz 64-QAM OFDM signal in experiments are used to validate the pro-posed DPD. The validation is illustrated in the means of power spectrum, AM/AM and AM/PM distortion, and error vector magnitude (EVM) of the received signal constellations. The average EVM improvement by simulation for 3-band, 4-band, 5-band and 6-band signals is 19.97 dB, 18.65 dB, 16.64 dB and 15.44 dB, respectively. The average EVM improvement by experiments for 5-band signals is 8.1 dB. Considering the ten times of bandwidth difference, experiments and simulation agree well.

抑光载波双边带Radio over Fiber双工通信系统设计

提出并模拟证明了基于两个电光相位调制器实现抑光载波双边带(Radio on Fiber,RoF)双工传输系统设计方案.通过改变电光相位调制器的最大相偏量,实现了抑光载波双边带信号传输——使通信带宽加倍,而且很好地控制上下行传输信号的误码率.仿真模拟结果表明,发射功率为3dBm的光信号在无放大、色散系数为20ps/(nm.km)、衰减系数为0.25dB/km的SMF-28单模光纤中传输时,其超高频RF调制信号的频率可达24GHz,数据码元传输速率可达2.5Gbit/s,传输距离40km以上.

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.

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.

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.

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.

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.

The Optimization of Radio over Fiber Link by Proper Link Gain Control

we demonstrate the adjustability of optimal input power(OIP) of the radio over fiber(RoF) link by proper link gain control in the central unit(CU) and remote antenna unit(RAU).The experiment results show that the reading and writing distance(RWD)of the radio frequency identification(RFID)service and the throughput of the WiFi service have a max increase of 3cm and 6.975Mbit/s respectively when the OIP value equals to output power of commercial products,compared with OIP value with 5-dBm right/left shift to the output power.

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.

Photonic Vector Signal Generation by Frequency Sextupling for Radio Over Fiber Systems

To generate high-frequency radio frequency(RF) vector signals, a vector signal generation method by optical frequency sextupling using a dual-parallel modulator is proposed. The method modulates vector signal on +3 rd order optical sideband and local oscillator(LO) signal on-3 rd order sideband using the intermodulation process in the DPMZM. After suppressing of the optical carrier and other sidebands through proper adjustment for modulator biases and modulation index, a frequency sextupled millimeter-wave vector signal can be generated after photodetection. The frequency sextupling will lower the bandwidth of the modulator, the local oscillator and the driving circuits. In addition, the phase of generated signal is not distorted after detection, and the power fading after fiber transmission can be avoided. In the simulation, a 500-MSym/s QPSK signal at 60 GHz is generated by 10-GHz drive signal. After travelling over fiber with length of 20/30/40-km, receiver power penalty keeps below 2.5 dB.

Design and Modeling of S Band Circular Patch and Ka Band Horn Antenna, Integration with Future Multifunctional Radio over Fiber Network

Radio over Fiber is an integration of microwave and optical fiber technologies having numerous benefits. RoF technology can give a scope of advantages including the capacity for backing multiple radio services and standards. In coming future, there is need of integrated wireless service with high speed satellite broadband and multifunctional indoor/outdoor antennas. Radio over fiber is one of the most favorite candidates to meet all these requirements of future multifunctional integrated wireless communication. Due to planer profile, small size and low cost patch antennas are most favorite to use for multi- frequency applications. In this paper, we present system level design for future multifunctional radio over fiber network. Under FTTH (Fiber To The Home) technology, it will be possible to use multi-frequency applications on single fiber medium. Firstly, we designed S band circular patch antenna (2.5 GHz) and Ka band (29 GHz) horn antenna. Circular patch antenna performance is estimated with different substrate height. After getting S parameters and far-field results, we did modeling of Radio over Fiber system over (10 Km) with same parameters from antenna results.

Radio over Fiber Architecture Very High-Speed Wireless Communications in the Unlicensed 60 GHz Band

Larger wireless access networks are required to meet the growing demand for mobile traffic and multimedia services. The use of RoF (Radio over Fiber) technology in combination with millimeter waves is a potential response to the requirements of broadband applications and high capacity networks. In this paper, we proposed a RoF architecture able to provide very high-speed wireless access points up to Gbps considering an indoor and outdoor environment conform to IEEE 802.11ad and IEEE 802.15.3c standard. Optical transmission and radio coverage have been studied by considering the uplink and downlink. System performance has been evaluated in the relation to the Error Vector Magnitude (EVM) for various modulation formats (BPSK, QPSK and 16QAM). Results showed that millimeter wave signals are successfully delivered over a 50 km fiber link and a wireless channel up to 32 m. Data throughput up to 5.28 Gbps has been reached. The proposed architecture can extend the range of applications for wireless communications in association with the unlicensed 60 GHz band with the advantages of better capacity, a wider coverage area and a reduction in the investment cost.

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.

Green Architecture for Dense Home Area Networks Based on Radio-over-Fiber with Data Aggregation Approach

The high-density population leads to crowded cities. The future city is envisaged to encompass a large-scale network with diverse applications and a massive number of interconnected heterogeneous wireless-enabled devices. Hence, green technology elements are crucial to design sustainable and future-proof network architectures. They are the solutions for spectrum scarcity, high latency, interference, energy efficiency, and scalability that occur in dense and heterogeneous wireless networks especially in the home area network （HAN）. Radio-over-fiber （ROF） is a technology candidate to provide a global view of HAN＇s activities that can be leveraged to allocate orthogonal channel communications for enabling wireless-enabled HAN devices transmission, with considering the clustered-frequency-reuse approach. Our proposed network architecture design is mainly focused on enhancing the network throughput and reducing the average network communications latency by proposing a data aggregation unit （DAU）. The performance shows that with the DAU, the average network communications latency reduces significantly while the network throughput is enhanced, compared with the existing ROF architecture without the DAU.

Development of Millimeter-Wave Radio-over-Fiber Technology

Millimeter-wave radio-over-fiber techno- logy demonstrates the potential for providing wireless broad-band service in the next generation wireless communication system.Optical generation of millimeter-wave signal is one of the most important technologies of millimeter-wave radio-over-fiber system.The virtues and shortcomings of some ways of optical generation of millimeter-wave signal are discussed.Then optical millimeter-wave signal transmission perfor- mance is described.Finally,an overview of the millimeter-wave radio-over-fiber system is given.It is suggested that the millimeter-wave radio-over-fiber technology should be paid more attention,especially for modulators for optical generation of millimeter-wave signal and radio-over-fiber system.

Optical QPSK/16QAM modulation based on serial-parallel MZM scheme in radio-over-fiber system

A novel scheme of optical modulation in 40 GHz radio-over fiber （RoF） system is proposed. It generates optical QPSK/16QAM signals in a serial-parallel structure of Mach-Zehnder modulators （MZMs）. The millimeter-wave is obtained with optical frequency multiplication （OFM）. Furthermore, modulation on optical-wave is transferred onto millimeter-wave. It can be used to increase transmission capacity of millimeter-wave RoF systems.

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.

WiFi over Fiber Link and Wavelength Assignment Protocol for Internet of Things

A novel Wireless Fidelity (WiFi) over fiber link and a wavelength assignment protocol are proposed to provide sufficient bandwidth and extensive coverage range for the various applications in the Internet of Things (IoT).The performance of the WiFi over fiber-based wireless IoT network is evaluated in terms of error vector magnitude (EVM) and data throughput for both the up and down links between the WiFi central control system and remote radio units (RRUs).The experimental results illustrate the reliability of the fiber transmission of 64 Quadrature Amplitude Modulation (64QAM) WiFi signals by direct analog modulation.In order to efficiently utilize the wavelength resources,we also demonstrated the wavelength assignment protocol by employing optical switching configurations in Central Station (CS) to realize the wavelength switching,and the simulation results indicate the queuing size and the corresponding queue delay for different numbers of available wavelengths.