基于外调制器的全双工无线信号光传输系统

提出了一种基于双平行马赫 增德尔调制器的全双工矢量信号传输系统。传统的光学倍频技术只适用于NRZ (not return to zero) 等强度调制格式,而不适用于无线通信中常用的MPSK、MQAM等矢量信号调制技术,用传统的倍频技术生成光毫米波后,用滤波器将其2个边带分开,在其中一个边带上调制矢量信号,这样幅度和相位信息被正确保留,且使用了8倍频模块,降低了传输过程中对光电器件的带宽要求。理论分析和仿真结果表明:通过此方法产生的携带在60 GHz载波上的625 Msymbol/s的4QPSK信号,经过20 km单模光纤传输后,误差向量幅度损耗可以忽略不计。     

基于级联MZMs倍频系数可调的相位编码信号光产生方法

提出了一种基于级联马赫-曾德尔调制器(MZMs)倍频系数可调的相位编码信号光产生方法。该方法的系统核心器件为级联MZMs,通过合理选择两个MZMs的直流偏置电压和调制指数等参数,可任意选取±k(k=1,2,…,5)阶边带中的一组边带。通过可编程光滤波器滤除5阶以上的高阶边带,再结合相位调制,可产生载波2、4、6、8和10倍频的相位编码信号。该方法是通过改变施加在级联MZMs上的射频驱动信号幅度实现倍频系数调节,方案简洁灵活。通过仿真实验验证了利用4GHz的微波信号源分别产生载频32GHz和40GHz的相位编码信号,从而实现了8和10倍频信号输出,且所生成的相位编码信号具有很好的脉冲压缩性能。     

频率可调的双路相位编码微波信号系统

提出一种在单输入情况下同时产生两路任意相位编码微波信号的方法,不仅可以保证编码信号180°的相移,还可实现编码信号的频率大范围调谐.建立由一个双平行马赫曾德调制器和一个保偏布拉格光栅组成的系统,激光输入双平行马赫曾德调制器调制后,通过保偏布拉格光栅与偏振分束器的共同作用产生两路偏振正交的±2阶边带.其中一对边带经过相位调制器调制后与另一对耦合,最后输出两个光电探测器拍频得到高频率、低噪声的相位编码微波信号.仿真结果表明,通过调节驱动信号的频率,可得到5～100 GHz的一系列四倍频相位编码微波信号.还原的相位信息与脉冲压缩比均和理论值吻合,证明了所提方法具有良好的脉冲压缩性能.     

基于光载波抑制调制的可调谐高倍频毫米波信号发生器

提出了一种基于改进的光载波抑制调制方式的光学生成高倍频可调谐毫米波的方案.该方案利用均匀光纤光栅型声光可调谐滤波器选取光载波抑制信号中的两个边带分量进行拍频,实现高倍频且倍频因子可调的毫米波信号的生成.为避免色散所致的码元时移效应,将基带数据信号仅调制到光载波抑制信号的一个边带分量上.仿真验证了倍频因子分别为2,6,10,14,18和22的毫米波信号的生成.另外,对22倍频下的光载无线电系统的链路性能进行了仿真分析,毫米波信号在调制2Gbit/s的非归零码型数据信号经50km的光纤传输后,系统的眼图仍保持良好的睁开度,链路的功率代价仅为0.4dB.系统具有良好的传输性能,可以满足通信系统的需求.     

基于载波抑制单边带调制的微波光子本振倍频上转换方法

提出了一种基于载波抑制单边带调制的微波光子本振倍频上转换方法.通过将本振信号加载在马赫-曾德尔调制器上产生±1阶本振边带,利用光纤光栅进行边带分离,将–1阶本振边带作为载波输入双平行马赫-曾德尔调制器进行二次调制.中频信号通过90°电桥加载在双平行马赫-曾德尔调制器上,并使其工作在载波抑制单边带调制状态.最后将输出的中频单边带调制信号与光纤光栅反射的+1阶本振单边带信号进行合路拍频,即可获得频率为2w_(LO)+w_(IF)的上变频信号.为了验证该方法的有效性,搭建了上变频链路并进行了性能测试,实验结果表明链路的输出光谱和频谱较为纯净,经过单边带调制后的光谱杂散抑制比达到了22.5 dB,产生的本振倍频上转换信号的杂散抑制比达到了23.6 dB,系统的无杂散动态范围达到了96.1 dB·Hz~(2/3).该本振倍频上转换方法可有效降低对本振信号的频率需求,并且产生的上转换信号纯净度较高,为光载无线通信、光控相控阵雷达等系统中的高频发射提供了有效途径.     

基于高阶受激布里渊散射的高频微波信号产生技术

对受激布里渊散射(SBS)信号产生的过程及原理进行了分析,提出了一种利用环腔多次放大产生多级布里渊散射信号的方法,并通过实验产生了较为稳定的1～6阶散射信号。在此基础上,提出了一种利用环腔所产生的四阶布里渊散射信号对经马赫-曾德尔调制器(MZM)调制产生的四阶边带信号进行选择放大,而后将被放大了的高阶边带信号与载波信号进行拍频,从而获得高频微波信号的简单方法。该方法仅需要一个掺铒光纤放大器(EDFA)就可以产生高达n(1≤n≤6)倍于11GHz的微波信号,具有器件成本低、倍频效率高的优点。仿真和实验结果证实该方法是可行的。     

基于布里渊载波相移的宽带可调谐二倍频微波信号生成

本文提出并实验验证了一种基于光纤中受激布里渊散射效应的光子二倍频微波信号生成技术.利用布里渊增益谱内的强色散特性,对光强度调制器产生的双边带调制信号的载波进行π/2相移,可实现载波与±1阶边带拍频仅生成二倍频微波信号.由于光纤中受激布里渊散射的窄带特性以及仅对双边带调制信号的载波进行相移,不影响调制信号两个边带的幅值和相位,因而生成的二倍频微波信号可实现宽带调谐,调谐范围仅受其他光器件的工作带宽限制.此外,信号光和产生受激布里渊散射的抽运光均来自同一光源,因而不受波长漂移的影响,系统具良好的稳定性.     

利用法布里-珀罗腔抑制电光相位调制中的剩余幅度调制

激光经电光相位调制后,由于剩余幅度调制的存在造成调制边带幅度不相等。利用法布里-珀罗腔的透射特性和Pound-Drever-Hall技术对通过法布里-珀罗腔的调制光正、负一级边带的幅度产生不同的衰减,使得调制边带的幅度相等,从而实现对电光相位调制中剩余幅度调制的抑制。采用该方法,理论上计算了调制光经法布里-珀罗腔后的光外差光谱信号,获得锁定法布里-珀罗腔后调制边带幅度的不对称度较腔锁定前减小四个数量级。实验研究了调制光经法布里-珀罗腔透射的光外差光谱,结果表明将法布里-珀罗腔锁定于该透射光外差光谱中心零位时,对剩余幅度调制的抑制程度可达45 dB。     

一种改进的生成四倍频光毫米波的传输方案

针对光载无线通信系统中并联双驱动马赫-曾德尔调制器(MZM)的四倍频方案产生功率周期性衰落效应,以及传输距离短的不足,提出了一种改进的抑制双边带调制产生光毫米波方案。首先在并联MZM后用波分复用(WDM)分离抑制双边带信号的两个边带,将基带信号调制到下边带,再与未调信号耦合后产生光毫米波,最后传输至加入前置补偿的光纤链路中。用optisystem7.0软件对改进方案进行了仿真,结果表明用此类结构不仅能得到高纯度的四倍频光毫米波,还可以消除上述的效应,实现了更长距离、更佳性能的传输。     

承载正交频分复用信号的58GHz光载毫米波波分复用光纤无线通信系统

实验研究了一种采用马赫-曾德尔强度调制器和光交叉复用器(IL)产生58 GHz光载毫米波传输正交频分复用(OFDM)信号的波分复用光纤无线通信(WDM-ROF)系统。中心站的4路连续光波耦合后输入射频(RF)信号频率为29 GHz的强度调制器进行双边带(DSB)调制,再用另一个强度调制器将2.5 Gb/s的OFDM信号调制到DSB信号上。经20 km单模光纤(SMF)传输至基站,通过IL将中心载波和一阶边带分离。经可调谐光滤波器(TOF)滤取所需信道的一阶边带,由高速光电检测器产生58 GHz的电毫米波,利用相干解调恢复下行OFDM基带数据信号。实验结果表明,在无色散补偿和误码率为10-3的条件下,下行OFDM信号经光纤传输20 km后的功率代价小于0.5 dB,而且星座图依然清晰。     

Photon Generation Scheme of 32-Fold Millimeter-Wave Signal Based on Mach-Zehnder Modulator

This paper proposes a 32-tupling frequency millimeter-wave (MMW) filter-free system based on four Mach-Zehnder Modulators (MZM) connected in parallel and cascaded with a simple radio-fiber (RoF) link structure. The four MZMs are all at the maximum transmission point (MATP), and the radio frequency (RF) driving voltage phase difference between MZMs is π /2. The center carrier is suppressed by using an optical attenuator (OATT) and an optical phase shifter (OPS). Two parallel MZMs can generate ±8th order and ±12th order optical sidebands, and the ±4th order optical sidebands can be suppressed by adjusting the modulation index m of the MZM, using cascaded two dual-parallel MZMS(DPMZM) and the phase difference of the RF signal source is π/4 to generate ±16th order optical sidebands. The theoretical analysis and simulation experiments are performed for the scheme proposed in this paper. The results show that the simulated and theoretical values of the optical sideband suppression ratio (OSSR) for ±16th order optical sideband signals are 60.02 and 59.96 dB, respectively, and the simulated and theoretical values of the RF sideband suppression ratio (RFSSR) for the 32-tupling MMW signal are 56.34 and 53.94 dB, respectively.     

一种改进的双边带调制产生光毫米波的方案

提出了应用于光纤无线通信系统中一种改进的双边带调制产生光毫米波方案。在中心站采用强度调制将射频信号调制到光载波上产生一个双边带信号,滤掉中心载波后,利用光交叉复用器把双边带信号的上下边带模分开,将数据速率为2.5Gbit/s的基带信号调制到下边带模后,再与未调信号耦合后产生光毫米波,然后通过单模光纤传输至基站,在基站经过光电转换后产生电毫米波信号。从理论上对该毫米波的色散特性进行了分析,发现毫米波的接收功率不会周期的衰减。同时通过实验研究表明,下行链路信号通过光纤能传输50km而不需要色散补偿,功率代价小于1dBm。因此,该方法产生的光毫米波能有效克服光纤色散引起的信号时延而导致的基带信号退化,适合于远距离传输。     

Generation of radio signals using a novel Mach-Zehnder modulator with four arms

We have proposed and demonstrated a novel Mach-Zehnder modulation technique which employs a 1 × 4 multimode interference MMI coupler and four optical phase-modulator waveguides to generate optical single sideband (SSB) signals in radio-over-fiber (ROF) transmission link. It is shown that when the RF (radio frequency) modulation index is large, the optical SSB signal generated by conventional modulation scheme contains a significant part of undesired higher order harmonics, accordingly, much distortion in the RF signal was detected at the base station (BS). However, the main undesired higher order harmonics can be suppressed using our proposed modulation scheme and the performance of the transmission links were largely improved in single-channel and dense wavelength-division multiplexing (DWDM) cases.     

采用正交光功率比值的光子型微波频率测量方案设计

通过构建两个正交的光功率比值,以光子技术实施微波频率测量.首先,待测微波信号经外调制器加载到连续光源上,在单边带载波抑制调制下仅得到单个光边带;以光学梳状滤波器对其进行滤波处理,在输出端检测得到随微波频率增大而呈现余弦函数和正弦函数变化趋势的两个光功率;将这两个光功率与参考光功率进行比较后,进而得到余弦函数型和正弦函数...     

Simulation of Third-Order Intermodulation Distortion Suppression Incorporating Dual-Parallel Mach–Zehnder Modulator in a CR-SSB Modulation

A novel scheme is proposed to enlarge the spurious free dynamic range (SFDR) of microwave photonic (MWP) link by using dual-parallel Mach–Zehnder modulator, which modifies the single sideband signal and replaces the optical carrier with an unmodulated one to remove the optical main sources of third-order intermodulation distortion (IMD3). Simulation results show that the IMD3 and fifth-order intermodulation distortion can be suppressed greatly even when the modulation depth increases to a high value, and the link is limited by seventh-order intermodulation distortion and the SFDR is improved by 34.2 dB Hz in a 1-Hz bandwidth. The error vector magnitude of the MWP link with the proposed scheme is improved significantly for the transmitted 1-Gbit/s 16- quadrature amplitude modulation (QAM) signal.     

Frequency-octupled phase-coded signal generation based on carrier-suppressed high-order double sideband modulation

An approach for photonic generation of a frequency-octupled phase-coded signal based on carrier-suppressed high-order double sideband modulation is proposed and experimentally demonstrated. The key component of the scheme is an integrated dual-polarization quadrature phase shift keying modulator, which is used to achieve the carrier-suppressed high-order double sideband modulation. At the output of the modulator, two fourth-order optical sidebands are generated with the optical carrier suppressed. After that, a Sagnac loop incorporating a fiber Bragg grating and a phase modulator is employed to separate the two optical sidebands and phase modulate one sideband with a binary coding signal. The approach features large carrier frequency tuning range for the generated phase-coded signal from several megahertz to beyond the W-band. A proof-of-concept experiment is carried out. The 2 Gbit/s phase-coded signals with frequencies of 16.48, 21.92, and 29.76 GHz are generated.     

应用于ROF系统中的单边带调制微波毫米波生成技术研究

介绍了单边带调制微波毫米波生成技术研究的背景及意义,综述了几种主要的单边带调制微波毫米波生成技术方案,包括移相法、滤波法、非线性效应法,以及在此基础上的改进方法,如应用于ROF系统中基于谐波抑制的新型单边带调制方案、应用超窄双传输峰光纤光栅实现光学单边带调制等。还介绍了两种新型单边带调制生成微波毫米波技术,包括基于极性反转电光调制器的单边带调制技术以及新型光学注入锁定单边带调制实验系统     

Novel 60 GHz RoF system with optical single sideband mm-wave signal generation and wavelength reuse for uplink connection

In order to improve RF frequency to achieve higher bandwidth and larger capacity, we propose a novel scheme to generate optical single sideband (SSB) millimeter-wave, in which frequency doubling of local radio frequency (RF) is obtained by using one integrated Mach–Zehnder modulator (MZM), and we theoretically investigate the generating principle of SSB. The optical SSB modulation scheme is employed to generate 60 GHz optical mm-wave and the 2.5 Gb/s baseband signal is simultaneously up-converted at the central station (CS) for downlink transmission, and the optical carrier is reused for uplink connection at the base station (BS). The full-duplex 2.5 Gb/s data are successfully transmitted over 40 km standard single-mode fiber (SMF-28) for both uplink connection and downlink connection with less than 2-dB power penalty. Results show the novel 60 GHz RoF system with optical SSB mm-wave signal generation using optical frequency doubling is feasible and we can obtain simple cost-efficient configuration and good performance over long-distance transmission.     

A full-duplex radio-over-fiber system based on a novel double-sideband modulation and frequency quadrupling

We propose a novel radio-over-fiber system based on double-sideband (DSB) modulation and frequency quadrupling to reduce the system cost both at central office (CO) and base station (BS). In this system, by properly biasing the intensity modulator, the repetitive frequency of the optical millimeter-wave (mm-wave) is four times frequency of the local oscillator (LO) signal. Additionally, due to the single-sideband of the mm-wave carrying base data signal, our theoretical simulation shows that the generated mm-wave can be immunized the fading effect and the walk-off of signals.