基于级联马赫-曾德电光调制器的60GHz光载毫米波传输系统的研究

提出并实现了一种新的产生毫米波的六倍频技术。采用两个相同的串联马赫一曾德电光调制器（MZM）,调节第1个MZM调制器的偏置电压使其工作在最小传输模式,只输出奇次光谐波分量;调节第2个MZM调制器的偏置电压使其工作在最大传输模式,抑制所有的奇次光谐波分量。实验显示,采用10GHz的射频（RF）信号驱动这两台MZM调制器后...     

基于调制边带法的高次倍频光毫米波产生

提出了利用外调制技术的调制边带法的六倍频和八倍频光毫米波产生方案。方案仅采用一个马赫曾德尔调制器,并利用其非线性传输特性,通过调节MZM 的偏置电压和调制电压,控制边带的强度,仅保留三阶边带或四阶边带,从而实现六倍频及八倍频光毫米波的产生。采用将基带数据信号仅调制在一个三阶边带或四阶边带分量的方式,有效防止走离。数值分析结果表明,提出的方案仅需10 GHz 及7.5 GHz 的调制信号频率就能得到60 GHz 毫米波,大大减小了调制信号频率,增加了上变频系数,传输距离可达160 km,而功率代价变化不大。与提出的其他高倍频技术相比,由于系统仅采用一个马赫曾德尔调制器,提出的方案系统结构更为简单,且此方案色散影响较小,传输距离更长。     

双级联调制六倍微波光子传输链路设计

提出了一种新的可用于RoF(Radio over Fiber)系统的六倍频毫米波信号的产生方法,通过设置两级联MZM调制器各自的偏置状态,并联合控制它们之间的光载波时延以及驱动信号间的相位差,来产生六倍频毫米波信号.在毫米波信号模块产生的基础上,针对两种不同的数据加载方式,构建相应的下行传输链路,对光毫米波传输特性进行了理论分析和仿真验证.     

基于级联调制器和四波混频效应的24倍频微波信号的光学生成

提出了一种基于级联马赫-曾德尔调制器 (MZM)和半导体光放大器(SOA)的24倍频微波信号 光学生成方案,具有覆盖频段高、杂波抑制效果好等优点。在本方案中,低频微波信号分别 通过两个级联 MZM对连续光源进行调制,调节直流偏置使两个MZM均工作在最大偏置点,以抑制奇数阶光分 量;进一 步调节两个MZM的调制深度,并结合可调谐电相移器(TEPS)和可调谐光相移器(TOPS)引入相 移,完全抑 制第2个MZM输出的±2阶光分量和光载波,得到±4阶光分量;再经过SOA发生四波混频(FWM )效应,形成±12 阶光分量;滤波后拍频可以获得24倍频微波信号。最后,搭建了实验和仿真系统,分别以11．0GHz,11.5GHz和12.0GHz的微波信号为驱动,得到间隔为264、276GH z和288GHz的±12阶光边带,有效验证了方案的可行性。     

基于双平行PM调制的60GHz光毫米波RoF系统研究

提出了一种采用相位调制器产生六倍频光载毫米波的RoF系统。该系统使用一个双平行相位调制器实现六倍频的调制,通过调节相位调制器的相位偏移量,产生出抑制一阶边带的光谱,耦合相减后得到三阶边带信号,在光电检测器中拍频,产生六倍于射频信号的光载毫米波。仿真结果表明,10GHz射频信号可以产生60GHz光载毫米波信号,5Gb/s的数据信号可在单模光纤中传输10km以上。     

基于强度调制和布里渊效应的六倍频可调毫米波信号产生

提出了一种新型的基于马赫-曾德尔调制器(MZM)和布里渊效应实现六倍频可调毫米波信号输出的方法。在本方案中,先调节MZM的直流偏置,抑制偶数边带,留下奇数边带;经过大功率掺Er3+光纤放大器(EDFA)放大之后,使两个一阶边带的功率达到布里渊阈值之上,然后采用了25km的单模光纤(SMF)作为布里渊介质,滤除一阶边带,留下三阶边带;最后经过EDFA放大和光电探测器(PD)光电转换得到六倍频的毫米波信号。因为布里渊边带滤波是窄带滤波,与波长无关,故本系统可以实现波长无关的微波信号产生。     

导频自适应的电光调制器激光脉冲调制技术

为解决脉冲信号对导频产生干扰进而导致马赫-曾德尔电光调制器(MZM)工作点无法稳定的问题,提出了一种导频自适应的偏压控制技术。采用数字控制系统生成频率可变的导频,由快速傅里叶变换分析反馈信号的谐波分量,可以将MZM锁定于传输曲线的最低偏置点。通过实时监测偏置电压输出,自主改变导频频率,避免脉冲信号对导频的影响,实现了高消光比的激光脉冲调制。结果表明,激光脉冲的重复频率与导频一次谐波频率接近时,脉冲信号会影响调制器工作点的稳定,该系统可以实现导频频率在0.45～2 kHz范围内的自适应变化,满足不同重复频率的激光脉冲调制需求。脉冲峰值为10 V、占空比为10%时,调制光脉冲的消光比可达26 dB,相较于脉冲信号对导频产生干扰时,输出脉冲消光比提高了约24 dB。     

基于双平行MZM调制器和四波混频效应的高倍频微波信号的光学生成

提出了一种基于双平行Mach-Zehnder调制器(DPMZM ) 和半导体光放大器(SOA ) 的四波混频(FWM ) 效应的 24 倍频微波信号光学生成方案,具有覆盖频段高、系统结构简单 和 频谱纯度较高等优点。在本方案中,低频率的微波信号 通过 DPMZM 对光源进行调制,调节直流偏置点使 DPMZM 的两个子 MZM 和主 MZM 均偏置在最大传输点,抑制 所有 奇数边带,进一步调节两个子 MZM 的调制深度和移相器的相移,完全抑制光载波和二阶边带,得到±4阶光边带;再经 过 SOA 发生FWM效应 , 产生±12 光边带,经过光电探测器拍频后可获得 24 倍频的微波信号。最后,通过仿真实验, 以 10GHz 的微波信号为驱动信号,得到了 240GHz 的微波信号,验证了方案的可行性。     

基于偏置马赫-曾德调制器的微波光子信号倍频

高速光信号源在现代光通信中不可或缺,目前倍受研究者关注。提出了利用一种具有偏置控制的马赫-曾德尔调制器(MZM),采用倍频方案产生高速微波光子信号,并进行了实验研究。通过在MZM 上施加一定的直流偏置引起两臂光脉冲的相位差,使光脉冲发生分裂实现倍频。实验中,利用5 GHz 的射频信号源,成功获得了频率增加一倍的10 GHz 高质量高速光信号。同时,也可以观察到在不同偏置电压下会产生不同的脉冲序列,发现优化偏压是实现高质量倍频的必要条件。该方案可用于产生40 GHz 以上的高频率光脉冲,可广泛应用于高速光通信。     

一种基于并联DPMZM结构的无滤波器16倍频光生毫米波方案

提出了一种新的基于并联的双平行马赫曾德尔调制器(Dual parallel Mach Zehnder modulator,DPMZM)结构的光生毫米波方案,该方案无需滤波器即可产生高质量的16倍频毫米波。通过适当调节DPMZM下臂上的马赫曾德尔调制器(Mach Zehnder modulator,MZM)的偏置电压,可以灵活控制光的零阶边带的幅度;通过调节DPMZM上臂上MZM的调制系数和直流偏压,可以抑制奇次谐波;然后通过适当调节两DPMZM之间的相移,可以得到仅有±8阶边带的光谐波,后经光电探测器(Photo detector,PD)拍频得到高质量的16倍频毫米波信号。对16倍频毫米波产生的原理进行了详细分析,并通过仿真对方案的可行性进行了验证,光载波抑制比(Optical sideband suppression ratio,OSSR)为30.3 dB,RF杂散抑制比(Radio frequency spurious sideband suppression ratio,RFSSR)为23.5 dB。     

Polarization state rotation filter for optical generation of continuously tunable millimeter-wave signal employing an external intensity modulator

A method to generate a continuously tunable millimeter-wave signal employing an optical external intensity modulator and polarization state rotation filter (PSRF) is proposed. The technique is based on the optical heterodyne, the Mach–Zehnder modulator (MZM) is biased to suppress odd-order sidebands, and the polarization-dependent PSRF is used to filter the optical carrier. A concept-proof experiment system is built to demonstrate the generation of microwave signal by beating the generated two second-order optical components. The results show that a high purity tunable microwave signal with very narrow linewidth at four times the frequency of microwave drive signal can be obtained. Moreover, the generated signal does not suffer obvious phase-noise degradation after transmission through a 25-km SSMF link. The operation principle of PSRF and the effect of its performance on the generated electrical signal are also analyzed. The proposed technique based on PSRF is very easy to implement, flexible and cost-effective to generate continuously tunable millimeter-wave signals.     

基于马赫-曾德尔调制器的多种调制格式微波信号的光学生成研究

提出了一种基于马赫-曾德尔调制器(MZM)的 多种调制格式微波信号的光学一体化生成方案。 在本文方案中,微波信号和编码矩形波信号经合路器同时输入到MZM中,通过合理设置编码 信号的幅值使 MZM能够工作在其传输曲线的不同传输点,分别实现了频移键控(FSK)、二进制相移键控(BPSK)和 二倍频BPSK微波信号一体化生成。本文方案仅需要1个MZM而不需要额外加电的或光的选频器 件, 因此具有结构简单、可大范围调谐的优势。特别的,本文方案还可以产生二倍频的BPSK微波 信号,从 而使能够满足更高频的应用需求。在仿真和实验中,分别得到10/20 GHz的FSK、10GHz的BPSK 微波信号,同时产生了20GHz的二倍频BPSK微波信号,有效验证了本 文方案的可行性。     

Performance evaluation of optical OFDM in direct detected systems based on MZM bias and drive voltages

The impact of DC bias and the RF drive voltage of the dual electrode Mach Zehnder Modulator (DE-MZM) on the transmission performance of optical orthogonal frequency division multiplexing (O-OFDM) direct detected systems is analyzed theoretically and verified by simulation. Selection of optimum bias and drive voltage is necessary to minimize the optical signal to noise ratio (OSNR) requirements and the non-linear distortions in the fiber transmission. In this paper, we compare MZM modulation techniques such as double sideband full carrier and single sideband (SSB) [biased at quadrature and minimum power transmission (MPT) point] with a novel modified SSB OFDM technique. To the best of our knowledge for the first time, a mathematical model for above modified SSB technique is developed to evaluate the OSNR requirement, chromatic dispersion of the fiber, spectral efficiency and the receiver sensitivity against other modulation techniques. Our results show that the modified SSB technique provides high spectral efficiency, receiver sensitivity and low chromatic dispersion against other the modulation techniques, while the one biased at MPT minimizes the OSNR requirements.     

FSK Modulation Scheme for High-Speed Optical Transmission

In this paper,we describe the generation,detection,and performance of frequency-shift keying (FSK) for high-speed optical transmission and label switching.A non-return-to-zero (NRZ) FSK signal is generated by using two continuous-wave (CW) lasers,one Mach-Zehnder modulator (MZM),and one Mach-Zehnder delay interferometer (MZDI).An RZ-FSK signal is generated by cascading a dual-arm MZM,which is driven by a sinusoidal voltage at half the bit rate.Demodulation can be achieved on 1 bit rate through one MZDI or an array waveguide grating (AWG) demultiplexer with balanced detection.We perform numerical simulation on two types of frequency modulation schemes using MZM or PM,and we determine the effect of frequency tone spacing (FTS) on the generated FSK signal.In the proposed scheme,a novel frequency modulation format has transmission advantages compared with traditional modulation formats such as RZ and differential phase-shift keying (DPSK),under varying dispersion management.The performance of an RZ-FSK signal in a 4 × 40 Gb/s WDM transmission system is discussed.We experiment on transparent wavelength conversion based on four-wave mixing (FWM) in a semiconductor optical amplifier (SOA) and in a highly nonlinear dispersion shifted fiber (HNDSF) for a 40 Gb/s RZ-FSK signal.The feasibility of all-optical signal processing of a high-speed RZ-FSK signal is confirmed.We also determine the receiver power penalty for the RZ-FSK signal after a 100 km standard single-mode fiber (SMF) transmission link with matching dispersion compensating fiber (DCF),under the post-compensation management scheme.Because the frequency modulation format is orthogonal to intensity modulation and vector modulation (polarization shift keying),it can be used in the context of the combined modulation format to decrease the data rate or enhance the symbol rate.It can also be used in orthogonal label-switching as the modulation format for the payload or the label.As an example,we propose a simple orthogonal optical label switching technique based on 40 Gb/s FSK payload and 2.5 Gb/s intensity modulated (IM) label.     

Edge-Triggered Bi-Phase Modulation for the Generation and Modulation of UWB Pulses

We propose and demonstrate a novel scheme called edge-triggered bi-phase modulation for the generation and modulation of ultra-wideband (UWB) pulses in the optical domain. The proposed system consists of a laser diode, a Mach–Zehnder modulator (MZM), and a photodetector. An input data sequence with either return-to-zero or nonreturn-to-zero format is sent to the MZM via its radio-frequency port. The MZM is biased at the quadrature point; for an input pulse having a pulse amplitude equal to the two times the half-wave voltage of the MZM, a pair of UWB monocycles is generated with opposite polarities corresponding to the rising and falling edges of the input pulse. A proof-of-concept experiment is performed. A UWB monocycle sequence is generated when a square-wave with a frequency of 680 MHz is applied to the MZM. The generated UWB pulse has a 10-dB bandwidth of 5 GHz with a fractional bandwidth of 165%.