一种60GHz毫米波全双工光纤无线通信系统

为了实现有线信号和无线信号的同时传输,采用将有线信号和无线信号分别在两个正交的偏振态中构造混合网络的方法,用非对称输入的双臂马赫-曾德尔调制器来产生无线信号中的毫米波;利用相位调制器实现差分相位键控调制格式,以便在上行链路中实现载波重用有线信号,分别将调制后两个正交偏振态信号耦合到同一光波长上经过光纤传输至基站。在基站处将两个正交偏振态的信号分离,携带无线信号光载波经光电检测放大后由天线传输出去,而携带有线信号光载波分为两路,一路经过平衡检测器检测得到有线信号,另外一路应用到上行链路中实现载波重用。通过OPTICSYSTEM软件进行了理论分析和实验验证,得到了10Gbit/s有线信号和60GHz无线信号通过光纤传输50km后的眼图。结果表明,该方案传输效果很好。     

基于四倍频矢量信号和波长重用的双向光载无线系统

为提高光载无线(RoF)系统传输容量,提出了一种基于四倍频矢量信号生成及波长重用技术的双向RoF传输系统。该系统中,下行链路由基于受激布里渊散射效应的窄带光带阻滤波器和Sagnac环在光域实现四倍频矢量信号调制;在基站端,未调制的边带由检偏器滤出作为上行链路光载波实现波长重用。传输实验验证了24 GHz的四倍频正交相移键控(QPSK)信号的拍频产生,并测试了码率为400 Mbit/s的8 GHz下行频带QPSK和400 Mbit/s的上行基带开关键控(OOK)信号的6.15 km光纤传输。实验结果验证了该系统的可行性。     

基于光学倍频技术的WDM-ROF-PON系统设计

设计了一种将光载无线技术融合于波分复用无源光网络结构的系统。在发射端,系统采用光学倍频技术生成40GHz光毫米波载波,加载2.5Gbit/s的基带数据信号,下行链路传输性能良好且受色散影响小;在接收端,利用光波重用技术从下行信号中提取上行光载波,加载2.5Gbit/s上行基带数据信号。采用光学倍频技术降低了毫米波生成成本,提高了系统的实用性。     

一种多波段信号输出的全双工光载无线系统

为了提升通信系统的灵活性,扩大应用范围,同时降低建设成本,提出一种多波段信号输出的全双工光载无线系统。在单光源条件下,通过灵活控制偏振控制器、线性偏振器的角度,实现3路不同频段的下行矢量信号传输;利用载波重用和相干检测技术,实现上行基带信号输出。仿真结果表明：6 Gb/s四进制正交幅度调制（16QAM）信号经30 km光纤传输后,下行链路中5 GHz、45 GHz和25 GHz频段输出信号的最小误差矢量幅度（EVM）分别为5.66%、4.03%和2.67%,上行链路输出信号的最小EVM为4.01%。     

全双工光载无线通信链路模型研究

提出了一个新的全双工光载无线通信链路模型。方案的下行链路采用两个马赫曾德尔调制器级联以产生六倍频毫米波;采用单边带调制,有效防止了码元走离现象,提高了传输距离;上行链路复用了下行链路中的一阶光边带以作为上行基带信号的载波,从而无需在基站中额外配置激光源;采用延时零拍法解调,减少了对毫米波本地振荡器的需求,降低了系统的成本。仿真结果表明,所提出的全双工模型中,仅用10 GHz频率的调制信号就能产生60 GHz的毫米波,大大降低了调制信号频率,且下行链路传输距离可达250 km,而上行链路传输距离大于300 km。     

基于相位调制器产生光毫米波的全双工光纤无线通信系统

提出并实验研究了一种基于相位调制器产生光毫米波信号的全双工光纤无线通信(RoF)系统。在中心站采用相位调制器结合滤波的方法产生重复频率为40GHz的载波抑制双边带毫米波信号,利用交叉复用器分离开毫米波信号的上下边带,其中的一个边带强度调制数据速率为2.5Gbit/s的下行基带信号,另一个边带被发送到基站调制上行传输的基带数据。该系统抗色散效果好,在经过40km标准单模光纤上/下行传输数据速率2.5Gbit/s的基带信号后,双向的传输功率代价都小于0.5dBm。在光纤无线通信系统中采用相位调制器结合滤波的方法产生光毫米波,同时基于波长重用技术再生上行光载波信号,可以简化中心站和基站配置,节约系统成本。     

60GHz全双工OFDM-ROF系统的实验研究

研究了基于光外部调制的方式产生60GHz光毫米波的全双工光纤无线(ROF)通信系统。实验利用29GHzRF源产生58GHz的光载毫米波,2.5Gbit/s OFDM信号作为下行数据信号调制到光载毫米波上并传输光纤20km,在基站与用户单元实现3.3m的无线传输。同时实现了下行信号中心载波重利用作为上行信号的光载波,2.5Gbit/s的OOK信号作为上行数据信号调制到光载波上经20km上行链路光纤传输至中心站。     

利用低速数据口对卫星链路传输进行监测

1卫星传输 从播控中心传来的节目信号，经站外地面微波中继或光缆传输设备，送至上行站的基带终端设备对电视信号进行基带处理、信源编码、节目复用、信道编码等，成为符合卫星传输要求的基带信号。然后将基带信号送入发送系统，对70MHz中频载波进行调制，变频为6GHz上行信号，送HPA放大，最后馈送到天线系统向卫星发射。接收天线将卫星传送的电磁波接收下来，送至高频头，经低噪声放大和下变频后，送到接收机解调、解码、编码后得到节目信号，供监测使用或加入有线前端供用户使用。     

基于两个平行马赫-增德尔调制器的光载无线传输系统

为提高光载无线(radio over fiber,RoF) 传输系统中的光波信号的利用率,本文提出了一种基于两个平行马赫-增德尔调制器 (Mach-Zehnder modulator,MZM) 的RoF传输系统。两个平行MZM经射频(radio frequency,RF) 信号调制后,产生5个光边带信号,分别是正负一阶光边带、正负二阶光边带和光载波。其中正负二阶光边带使用基带数据进行调制,经光电检测器(photodiode,PD) 拍频后产生已调数据的毫米波信号,再由天线发射出去。正二阶边带和光载波经PD拍频后产生未调制数据的毫米波,该毫米波用于接收端解调的本振信号(local oscillator,LO) 。负二阶边带信号用于上行链路的光载波。在本系统中,5个光边带信号都被充分利用,提高了光信号的利用效率。此外,还分析了该系统通过色散介质的传输特性,为RoF通信系统提供了一种实用化的解决方案。     

改进的基于多倍频的单边带调制ROF全双工系统

利用单边带调制技术,设计了一种改进的毫米波光纤传输系统,进行了系统色散分析及仿真实验.该系统在中心站通过设置相位调制器的偏置电压,使调制器产生的奇数边带被抑制,采用滤波器滤出其中的一个二阶边带.基带信号经过中频调制形成副载波,再将此副载波通过单边带调制到二阶边带上;在基站,通过带通滤波器滤出上行链路所需的光载波.用该单...     

A Novel Scheme for Seamless Integration of ROF With Centralized Lightwave OFDM-WDM-PON System

We have experimentally demonstrated a novel transmission system for seamless integration of ROF with centralized lightwave OFDM-WDM-PON based on an integrated external modulator. At the one of two arms of the integrated external modulator, the optical carrier suppression (OCS) is realized to generate 40–GHz optical millimeter-wave (mm-wave) and up-converted baseband data signal as wireless signal. In another arm of the integrated external modulator, 16 quadrature amplitude modulation intensity-modulated OFDM signals at 10 Gbit/s are used for downstream transmission as wired signal based on double sideband modulation. By using one intensity modulator (IM), the downstream RF OFDM signal is remodulated for upstream on–off keying (OOK) data at 2.5 Gbit/s because of its downstream RZ shape waveform. The 10-Gbit/s wired signal, 2.5-Gbit/s wireless signal, and 2.5-Gbit/s upstream signal have been transmitted over 20-km single mode fiber (SMF) successfully.      

Full-duplex hybrid PON/RoF link with the 10 Gbit/s 16-QAM signal for alternative wired and 60 GHz millimeter-wave wireless accesses

A novel full-duplex hybrid access link with 10 Gbit/s 16-ary quadrature amplitude modulation (16-QAM) wired and wireless converged signal is proposed, which can provide PON access or RoF-based wireless access alternately with centralized lightwave source. The converged signal, consisting of the 10 Gbit/s 16-QAM baseband optical signal and two optical local oscillators (OLOs), is generated by central station and can be decomposed in different patterns at remote base station. For the wired PON access, the identical frequency OLO is used to coherently demodulate the 16-QAM signal; while for the RoF-based wireless access, the 16-QAM signal and its parallel polarized OLO are abstracted as optical millimeter wave by a polarization beam splitter; the other OLO is used as the uplink optical carrier to carry wired or wireless uplink signal. Since the three tones come from the same source, they maintain high coherency even after transmitted over fiber link. The proposed hybrid wired/wireless full-duplex fiber link suffers little from fiber chromatic dispersion. These are verified by simulations for both wired and wireless access applications.     

Full-duplex fiber-wireless link with 40 Gbit/s 16-QAM signals for alternative wired and wireless accesses based on homodyne/heterodyne coherent detection

A novel full-duplex fiber-wireless link with 40 Gbit/s 16-ary quadrature amplitude modulation (QAM) signals is proposed to provide alternative wired and wireless accesses for the user terminals. In the central station (CS), the downstream signal for wired and wireless accesses is beared onto the CW laser source via an optical I/Q modulator to realize the QAM modulation. At the hybrid optical network unit (HONU), a tunable laser is used to provide coherent optical local oscillator for homo-/heterodyne beating to coherently down-convert the baseband optical signal to the baseband electrical one for wired access or to the mm-wave one for wireless access according to the requirement of the user terminals. Simultaneously, the lightwave from the tunable laser is also used as the uplink optical carrier for either wired or wireless access, and is modulated colorlessly by the baseband or mm-wave signal of the uplink alternatively. After filtering, only one tone carrying the uplink signal is transmitted back to the CS even for the wireless access. The theoretical analysis and simulation results show that our proposed full-duplex link for the alternative wired and wireless accesses maintains good performance even when the transmission link with standard single mode fiber (SSMF) is extended to 30 km.     

Hybrid Access Network Integrated With Wireless Multilevel Vector and Wired Baseband Signals Using Frequency Doubling and No Optical Filtering

This letter experimentally demonstrated a hybrid access network which supports both radio-over-fiber and fiber-to-the-x systems. A 20-GHz radio-frequency (RF) 312.5-MSymbol/s M-ary phase-shift keying (PSK) signal and a baseband (BB) 1.25-Gb/s on–off keying signal are simultaneously generated and transmitted over an identical distributed infrastructure. The wired BB signal is compatible with the existing passive optical network (PON) system, and the wireless RF PSK signal can also share the same distributed infrastructure. The proposed system has no RF fading issue, no narrowband optical filter at remote node to separate the RF and BB signals, and can carry vector signals. Moreover, a frequency doubling for optical RF signal generation is achieved to reduce the bandwidth requirement of the transmitter. After transmission over 25-km standard signal-mode fiber, the receiver sensitivity penalties are less than 0.5 dB for both the RF and BB channels.      

TUNABLE FIBER FABRY-PEROT FILTER FOR OPTICAL CARRIER-SUPPRESSION AND SINGLE-SIDEBAND MODULATION IN RADIO OVER FIBER LINKS

A novel method of simultaneous realization of optical carrier-suppression and single-sideband modulation using fiber Fabry-Perot tunable filter is presented. In order to enhance transmission performance of radio over fiber links, we use a fiber Fabry-Perot tunable filter to filter out one sideband as well as suppress the optical carrier power. The results demonstrate 20.5dB and 14.2dB improvement in the signal noise ratios when 18GHz and 10GHz microwave signals carrying 5Mbit/s quadrature-phase-shift-keyed (QPSK) format data is transmitted over 35 km single mode fiber, respectively.     

光波调制技术的高级调制码型

Arbitrary waveform can be synthesized by two orthogonal components: in-phase and quadrature components. Thus, if we can manipulate the two components independently, various complicated modulation can be achieved. This technique is called vector modulation, which is commonly used in wireless radio communication systems where the carrier frequency is lower than 100GHz. On the other hand, in lightwave transmission systems, the carrier frequency is higher than 100THz, and the stability of the signal sources would be much poorer than in radio systems, so that the simplest modulation format (on-off-keying) was often used in commercial systems. However, recently, various modulation techniques such as quadrature amplitude modulation, etc., have been demonstrated by using precise and rapid lightwave control. In this report, we review recent progress in optical vector modulation technologies which can generate highspeed and complicated optical signals. Integrated optical modulators can synthesize multi-level signals in photonic circuits.     

Extending optical transmission distance in fiber wireless links using passive filtering in conjunction with optimized modulation

The authors demonstrate a simple passive technique for increasing the transmission distance in fiber wireless links through the application of a narrowband fiber Bragg grating (FBG) with high reflectivity (90-99%). They are applied in a conventional downstream link and also for the upstream in a wavelength-reused scheme. In the conventional nonwavelength-reused system, the grating is used to optimize the optical modulation depth and, hence, the receiver sensitivity in the downstream transmitted signal by reducing the power of the optical carrier before fiber transmission. In the wavelength-reused systems, the highly reflective FBGs can be effectively used at the base stations to recover a major portion of the optical carrier (as high as 99% of the downlink carrier) for uplink transmission from a weakly modulated downstream signal. In the latter case, the penalty in the downstream signal due to the large extraction of carrier power is partially offset by the sensitivity enhancement obtained in the filtering process. The authors present experimental results for the increased transmission performance for both the nonwavelength-reused and wavelength-reused scenarios. The increase in the sensitivity (at biterrorrate=10/sup -9/) in the nonwavelength-reused scheme for a given launch channel power that facilitates the increased transmission distance can be as large as 7 dB. The relative increase in the power margin for the upstream signal can be up to 4 dB in the wavelength-reused scheme. This would more than double the currently demonstrated transmission distances in such wavelength-reused systems without any optical amplification. The scheme is applicable to a wide range of radio frequencies and modulation depths.     

Coherent optical vector modulation for fiber radio using electrooptic microchip lasers

Future communication systems will require high data rates and flexible modulation. Direct optical phase modulation of two microchip lasers by information-bearing signals allows for high-rate delivery via fiber to a basestation. At the basestation, the coherent optical signals are combined with a reference in a photodetector to produce a microwave/millimeter-wave carrier with arbitrary M-ary quadrature amplitude modulation, which can then be transmitted over a wireless channel. Rapid tuning of the microwave/millimeter-wave carrier, the modulation scheme, and the data rate is achievable through this method with no fixed oscillators at the basestation, thus providing for flexible architectures. Results show a high-quality carrier and, for 4- and 16-QAM, with data rates to 200 Mb/s. Extensions to higher data rates are discussed.     

Multi-service small-cell cloud wired/wireless access network based on tunable optical frequency comb

In this paper, we demonstrate a novel multi-service wired/wireless integrated access architecture of cloud radio access network (C-RAN) based on radio-over-fiber passive optical network (RoF-PON) system, which utilizes scalable multiple-frequency millimeter-wave (MF-MMW) generation based on tunable optical frequency comb (TOFC). In the baseband unit (BBU) pool, the generated optical comb lines are modulated into wired, RoF and WiFi/WiMAX signals, respectively. The multi-frequency RoF signals are generated by beating the optical comb line pairs in the small cell. The WiFi/WiMAX signals are demodulated after passing through the band pass filter (BPF) and band stop filter (BSF), respectively, whereas the wired signal can be received directly. The feasibility and scalability of the proposed multi-service wired/wireless integrated C-RAN are confirmed by the simulations.