DRZ和MD-RZ码光纤传输性能分析

介绍了光双二进制归零码DRZ和改进的双二进制归零码MD-RZ的产生原理和特点,通过光通信仿真软件产生了这两种信号,并给出了光谱图.重点设计了一个40Gb/s的单信道光纤传输系统,对两种码型进行了模拟,通过对Q值的结果来分析其非线性容限和传输距离,并与CSRZ码的传输性能进行对比.     

100G OTN大容量传输技术解析

从OSNR性能改善、色散(CD)容限、偏振模色散(PMD)容限、相位调制、偏振复用等方面介绍了100G PM-QPSK关键技术特性,最后给出了烽火通信推出的100G大容量传输系统的解决方案.     

40Gb/s光纤传输系统中四种调制格式的性能比较

使用Opt i s ys t em软件,对40Gb/s单信道传输系统中非归零(NRZ)、归零(RZ)、光双二进制(ODB)、改进的光双二进制归零(MD-RZ)四种调制格式进行仿真。长距离传输后,MD-RZ的眼睛睁开度最大,Q值也很高,具有较好的色散容限和非线性容限,适合长距离传输。     

CS-RZ码在高速系统中传输性能的研究

文章介绍了栽波抑制归零码(CS-RZ)的产生机制及其优良的传输性能,并采用计算机仿真比较了CS-RZ、非归零(NRZ)和归零(RZ),这三种码在40Gbit／s速率下的传输性能．CS-RZ码抗自相位调制(SPM)比较好,而且有高的色散容限．从色散容限和SPM容限的角度来说,CS-RZ码是一种最好的调制格式．     

编码技术对传输系统性能改善研究

在超长距离传输时,信号调制格式是可提高系统传输性能的一项关键技术.先进的信号调制格式将提高系统的色散、非线性容限,延长系统传输距离.文章简要介绍了基于强度调制的NRZ、RZ和CSRZ三种编码的产生原理,并通过仿真分析了它们在不同速率下的抗色散和非线性的能力,最后采用CSRZ码对系统进行优化设计.     

40Gbps调制格式的仿真研究

针对不同调制格式应用于40Gbps系统的传输特性,分别从极限光信噪比、色散容限、PMD容限和非线性效应四方面得到仿真数据,并理论分析其产生原理。     

FSR优化后的DPSK解调的研究

文章仿真验证了在差分相移键控(DPSK)解调时,通过调整延时线干涉仪(DLI)两臂的相对延迟来优化自由光谱范围(FSR),使其大于传输比特率,能够获得比传统1 bit延迟更好的传输性能,并得到了FSR的最优值.优化FSR后的DPSK解调系统时光信噪比(OSNR)灵敏度和色度色散容限范围均有改善,对偏振模色散(PMD)的容忍度没有明显提高.     

架空光缆传输系统漂摆特性的研究与测试

在通信系统中,受天气、温度等变化的影响,传输媒质与设备中会出现传播延迟的变化;由此会引起所传数字信号的有效瞬间长时间地偏离其理想位置.这种现象称漂摆.随着光缆长途干线、尤其是架空光缆干线工程的大规模建设,漂摆作为一个系统特性指标、也应予以考虑并计算.应成为光缆工程设计的内容.本文简单介绍漂摆与滑动的关系,介绍他们的容限标准与指标分配,以及漂摆在光缆传输系统中的容限与分配、计算和测量.     

TLK2521的Refclk抖动分析

阐述了参考时钟存在较严重抖动的特定系统应用中TLK2521的性能,描述数据速率不同时PLL带宽变化情况,并据此得出时钟抖动传输特性.给出了在诸如传输线路长度超过36英寸的背板等特定应用中,TLK2521可以承受的时钟抖动容限.     

100 Gbit/s级联交错相位调制码型信号的传输性能

介绍了一种应用于100 Gbit/s传输系统的新型光信号调制码型--交错差分相位调制码(SDPSK).该码型的解调仅通过一个1 bit延时的马赫曾德尔延时干涉仪和一个平衡接收机即可实现.与传统的4种级联相位调制码型进行长距离传输特性比较后证明:基于NRZ码和50%占空比RZ码的SDPSK码与相同包络的DPSK码具有几乎相同的色散容限和一阶偏振模色散容限;与有相同包络的DPSK信号和差分四相相移键控码(DQPSK)信号相比,基于NRZ码和RZ码的SDPSK信号具有更高的抵抗非线性负面效应的能力:经过90 km普通单模光纤传输并采用16 km色散补偿光纤进行后置色散补偿后,通过带宽值大于125 GHz的三阶高斯滤波器检测光信号,RZ-SDPSK信号的接收性能最佳.     

高速光通信系统调制格式的仿真研究

使用光通信系统仿真软件,对非归零（NRZ）、归零（RZ）、载波抑制归零（CS-RZ）和归零差分移相键控（RZ-DPSK）四种调制格式信号在40Gb/s单信道传输系统中的非线性效应和色散容忍度进行比较,并对四种格式信号在G.652光纤中的长距离传输进行了仿真,结果表明：CS-RZ具有更优的抗噪声能力,RZ-DPSK格式具有更优的非线性容忍度。在噪声受限系统中,G.652光纤作为传输介质,CS-RZ格式的传输性能最优。     

Amplitude Regeneration of RZ-DPSK Signals in Single-Pump Fiber-Optic Parametric Amplifiers

The input power tolerance of a single-pump fiber-optic parametric amplifier (FOPA) is experimentally shown to be enhanced for return-to-zero differential phase-shift keying (RZ-DPSK) modulation compared to RZ on–off keying modulation at 40 Gb/s. The improved nonlinear tolerance is exploited to demonstrate amplitude regeneration of a distorted RZ-DPSK signal in a gain-saturated FOPA. An optical signal-to-noise ratio penalty of 3.5 dB after amplitude distortion is shown to be reduced to 0.2 dB after the FOPA, thus clearly demonstrating the regenerative nature of saturated FOPAs for RZ-DPSK modulation.      

10Gb/s和40Gb/s RZ-DPSK电预失真系统中非线性效应的研究

通过仿真研究了10和40Gb/s RZ-DPSK电预失真(EPD)系统中的自相位调制(SPM)和交叉相位调制(XPM)等非线性效应。EPD系统中的非线性效应比光色散补偿(ODC)中的大,但在不同比特率下非线性效应不同。对800km标准单模光纤(SSMF)传输的仿真的结果表明:单信道传输时受到SPM影响,比特率为10Gb/s的EPD系统的非线性阈值比ODC系统的小6dBm以上,而当比特率为40Gb/s时的EPD系统非线性阈值只比ODC系统小2dBm。波分复用(WDM)系统中受到SPM和XPM的影响,比特率为10Gb/s的EPD系统的非线性阈值比ODC系统的小6dBm,而比特率为40Gb/s时的EPD系统非线性阈值比ODC系统的小2dBm。研究结果表明,当比特率升高时,EPD系统的非线性效应减弱。     

A comparative study of DPSK and OOK WDM transmission over transoceanic distances and their performance degradations due to nonlinear phase noise

We have compared experimentally the transmission performance of return-to-zero differential phase-shift keying (RZ-DPSK) with RZ-ON-OFF keying (OOK), nonreturn-to-zero differential phase-shift keying (NRZ-DPSK), and NRZ-OOK for 100/spl times/10-Gb/s transmission with a spectral efficiency of 0.22 b/s/Hz over transoceanic distances. The Q degradation of the RZ-DPSK after transmission over 9180 km was 3 dB greater than that of RZ-OOK. The experimental results clearly showed the major cause of degradation for DPSK is not cross-phase modulation but self-phase modulation. The calculated nonlinear phase noise, i.e., the Gordon-Mollenauer effect, agreed with the experimental results. A distributed-Raman-amplifier assisted erbium-doped-fiber-amplified transmission line acted well in reducing the nonlinear phase noise.     

RZ-DPSK field trial over 13 100 km of installed non-slope-matched submarine fibers

This work presents the first field trial using the return-to-zero differential-phase-shift-keying (RZ-DPSK) modulation format. A 96/spl times/10-Gb/s RZ-DPSK field trial was conducted over a 13 100-km optical undersea path by double passing the installed 6550-km underwater link which was deployed with non-slope-matched submarine fibers. All channels performed with more than a 3-dB forward-error correction margin, including channels that accumulated over /spl plusmn/13 000ps/nm of dispersion. It is also shown that the RZ-DPSK format has similar residual dispersion and channel power tolerance for both slope-matched and non-slope-matched fibers. Furthermore, it is demonstrated that the chirped RZ-DPSK format could further improve system performance by 1-2 dB.     

Duty-ratio control of nonlinear phase noise in dispersion-managed WDM transmissions using RZ-DPSK modulation at 10 Gb/s

The authors compare analytical and numerical estimates, showing that the nonlinear phase noise of short optical pulses associated with the coupling between amplified spontaneous emission noise and fiber nonlinearity may be controlled by adjusting the duty cycle of the return-to-zero (RZ) signal modulation format. The impact of this effect in the optimization of the performance of 10-Gb/s dispersion-managed wavelength division multiplexed (WDM) systems using RZ-differential phase-shift keying (DPSK) modulation is discussed. By extensive numerical simulations, it is shown that the transmission quality of ultradense WDM systems using the RZ-DPSK modulation format may be significantly enhanced by optimizing the duty cycle of the RZ pulses.     

RZ-DPSK传输系统相位噪声的比较分析

建立了单信道40Gbit／s归零-差分相移键控码（RZ-DPSK）传输系统模型，详细地分析并比较了线性相位噪声和非线性相位噪声对系统性能的影响。结果表明，由放大器自发辐射（ASE）噪声带来的线性相位噪声对传输系统的性能影响最大，ASE与自相位调制（SPM）相互作用引起的Gordon-Mollenauer（G-M）相移次之，带内四波混频（IFWM）的影响最小。在最优输入功率的条件下，由ASE带来的线性相位噪声引起的系统差分相位Q值代价大于204dB，由G-M相移引起的系统差分相位Q值代价小于7．5dB。仿真结果表明，对于采用掺铒光纤放大器（EDFA）级联放大的单信道40Gbit／s RZ-DPSK传输系统，ASE噪声是限制系统无中继传输距离的最主要因素。     

Fiber Optic Video Transmission Employing Square Wave Frequency Modulation

Investigations are carried out on the performance of video transmission systems employing square wave frequency modulation (SWFM). A simple formula for the signal-to-noise ratio (SNR) in the SWFM video transmission systems is derived. The SNR performance is compared to that of frequency modulation (FM) and pulse frequency modulation (PFM). SWFM is shown to display the greatest receiver sensitivity when the fiber 6 dB bandwidth is less than 100 MHz. Video transmission experiments demonstrate the advantages of the SWFM, including 1) degree of simplicity in modulation/demodulation circuits as well as in optical transmitter and receiver circuits, 2) tolerance to nonlinearities in the system, and 3) insensitivity to the fiber baseband frequency-phase characteristics. Both the theoretical and experimental results have made clear the superiority of SWFM optical video transmission systems in application to CATV distribution systems and subscriber loop systems.     

光双二进制技术在城域光网络中的应用

对一种新型光部分响应数字传输技术即光双二进制技术的特点与发展趋势进行了深入研究和介绍。在详细阐述光双二进制系统的实现原理及主要实现方式,并介绍该技术的主要性能优越性以及近来研究成果的基础上,认为由于其与非归零等传统调制方式相比所具有的色散容忍度大、频谱窄、频带利用率高等诸多优点,使其在城域光纤网中的广泛应用正在日益成为可能。     

Investigation of Multilevel Phase and Amplitude Modulation Formats in Combination With Polarization Multiplexing up to 240 Gb/s

We present experimental investigations of the receiver sensitivity and dispersion tolerance of multilevel optical communication systems with a symbol rate of 40 Gbaud. Four- and eight-level communication is obtained by combining binary amplitude modulation with either binary or quadrature differential phase modulation. We experimentally compare the dispersion tolerance, and show that multilevel modulation formats offer much better dispersion tolerance compared to binary formats. By combining multilevel modulation with polarization multiplexing, bit rates up to 240 Gb/s were obtained. We demonstrate transmission over 50-km fiber span with no power penalty for a pseudorandom binary sequence length of$2^7-1$bits.