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．     

三种载波抑制归零码光调制格式性能

首先分析了基于载波抑制归零码的光载波抑制归零-开关键控(CSRZ-OOK)、载波抑制归零-差分相移键控(CSRZ-DPSK)和载波抑制归零-差分正交相移键控(CSRZ-DQPSK) 三种光调制格式的时域和频域特性,并数字仿真了其在40 Gbit/s单信道光纤系统中的传输性能.以Q值、眼图和误码率(BER)作为性能评价指标,研究了这三种调制格式对色散(CD)、偏振模色散(PMD)和非线性效应的抑制作用.结果表明:CSRZ-DQPSK相对于CSRZ-OOK、CSRZ-DPSK对色散、偏振模色散和非线性效应有非常好的容忍能力.     

40Gb/s光通信系统不同码型传输性能分析

使用Optisystem仿真工具,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)四种码型在40Gb/s单信道传输系统中的灵敏度、非线性效应和色散容忍度进行比较,并对标准单模光纤(G.652)中四种码型的单信道40Gb/s长距离传输进行了仿真,结果表明:CS-RZ具有更优的灵敏度和抗噪声能力,RZ-DPSK码具有更优的非线性容忍度.在较低入纤功率条件下,G.652光纤作为传输介质,CS-RZ系统的传输性能最优.     

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。     

高速光传输系统中八进制差分相位幅度键控性能分析

高级光调制格式能够有效抑制随信道速率的增加而给系统带来的色散、非线性等传输损伤,是高速光传输系统的关键技术之一.研究了基于马赫-曾德尔凋制器(MZM)产生的八进制差分相位幅度键控非归零码(NRZ-ODPASK)、八进制差分相位幅度键控归零码(RZ ODPASK)以及八进制差分相位幅度键控载波抑制归零码(CSRZ-0DPAsK)在40 Gbit/s速率下的传输性能.结果表明,RZ-ODPASK调制格式抗色散能力较强,且相位支路的色散容限均大于幅度支路;在波分复用(WDM)系统中,CSRZ-ODPASK信道间串扰代价比NRZ-ODPASK和RZ-ODPASK分别小0.81 dB和0.19 dB,更加适合高速光纤传输系统.     

16×40Gbit/s DWDM系统色散补偿和调制方式研究

对传输容量为16×40Gbit/s、传输距离为500～2 000km的DWDM(密集波分复用)系统进行了研究。分析了不同调制方式(CSRZ(载波抑制归零)码、DRZ(双二进制归零)码和MDRZ(改进的双二进制归零)码)、不同色散补偿方案(前置、后置和中间色散补偿)对系统传输性能的影响。仿真结果表明,当传输距离超过1 500km后,MDRZ码能够很好地抑制FWM(四波混频)效应,提高系统性能;中间色散补偿方案比前置色散补偿和后置色散补偿有更好的补偿效果。     

高速密集波分复用系统中的二级调制格式研究

论述了强度调制直接检测(IM-DD)高速密集波分复用(DWDM)系统的二级调制原理，并从马赫-曾德尔调制器的传递特性出发推导了四种调制格式[全频率调制归零码(FFMRZ)、半频率调制归零码(HFMRZ)、单边带调制归零码(SSBRZ)、载波抑制归零码(CSRZ)]。根据信号光眼图及归一化频谱描述了各种码型的时频特征。在此基础上分别对各种码型的色散容限、非线性容限进行了数值仿真，通过比较眼图张开度损伤(EOP)发现对于单波长系统载波抑制归零码传输性能最优。最后利用全面的密集波分复用系统模型计算了各种码型的Q因子，发现载波抑制归零码的性能仍然保持最优，这种优势在考虑偏振模色散(PMD)的情况下更为突出。因此载波抑制归零码是强度调制直接检测系统较好的选择。     

NRZ码和CSRZ码在40 Gbit/s单通道系统中传输性能分析

文章仿真了非归零码(NRZ)和载波抑制归零码(CSRZ)在40 Gbit/s单通道系统中G.652光纤上传输6×80 km的性能.比较了两种码型对接收端光滤波器和电滤波器带宽的要求、不同的入纤功率下功率代价以及残余色散对比.结果表明,在高速传输系统中,CSRZ码的传输性能明显优于NRZ码.     

基于马赫-曾德尔调制器的先进调制格式的产生

提出了一种基于差分马赫-曾德尔调制器(MZM)产生80 Gbit/s高速率差分相移键控归零码(RZ-DPSK)、差分相移键控载波抑制归零码(CSRZ-DPSK)、差分正交相移键控归零码(RZ-DQPSK)、差分正交相移键控载波抑制归零码(CSRZ-DQPSK)的新方法.在采用两个差分MZM级联产生数据速率为80 Gbit/s的RZ/CSRZ-DPSK光信号的基础上,仅需增加一个双驱动MZM,就可以产生RZ/CSRZ-DQPSK信号,说明提出的方法有一定的扩展性,并简化了高速RZ/CSRZ-DQPSK光信号的产生过程.对产生的80 Gbit/s RZ/CSRZ-DPSK和RZ/CSRZ-DQPSK信号进行的仿真结果表明,CSRZ-DPSK信号比RZ-DPSK信号的频谱结构更加紧凑,差分正交相移键控(DQPSK)光谱形状与差分相移键控(DPSK)相同,只是由于RZ/CSRZ-DQPSK在码元速率下传输数据,得到的光谱在频域被压缩.     

新型调制格式在PMD补偿技术中的应用

文章通过仿真得到了非归零(NRZ)码、载波归零(CSRZ)码、NRZ-差分相移键控(DPSK)和CSRZ-DPSK信号在偏振模色散(PMD)补偿前后的偏振度(DOP)值和剩余差分群时延(DGD)值.结果表明,与二进制强度调制(OOK)格式相比,DPSK补偿后的DOP值更多地分布在接近1的范围,剩余DGD值也较小,其中CSRZ-DPSK补偿效果最好,是实现PMD缓解与补偿动态结合的首选调制格式.     

Novel modulation and detection for bandwidth-reduced RZ formats using duobinary-mode splitting in wideband PSK/ASK conversion

This paper proposes a novel duobinary-mode-splitting scheme that uses wideband phase-shift-keying (PSK)/amplitude-shift-keying (ASK) conversion for modulation and detection of bandwidth-reduced return-to-zero (RZ) modulation formats. We have first demonstrated that the proposed scheme greatly simplifies the modulation process of the duobinary carrier-suppressed RZ format (DCS-RZ) based on baseband binary nonreturn-to-zero (NRZ) modulation. We also proposed carrier-suppressed RZ differential-phase-shift-keying format (CS-RZ DPSK) as a novel bandwidth-reduced RZ format by applying the proposed scheme in the detection process. These novel RZ formats are shown to be very useful for dense wavelength-division multiplexed (DWDM) transport systems using high-speed channels, over 40 Gb/s, with spectrum efficiencies higher than 0.4 b/s/Hz. We demonstrate that the proposed modulation and detection scheme greatly simplifies the DWDM transmitter and receiver configuration if the periodicity of the optical PSK/ASK conversion filter equals the WDM channel spacing. The large tolerance of the formats against several fiber nonlinearities and their wide dispersion tolerance characteristics are tested at the channel rate of 43 Gb/s with 100-GHz spacing. The novel CS-RZ DPSK format offers higher nonlinearity tolerance against cross-phase modulation than does the DCS-RZ format.     

WDM field trials of 43-Gb/s/channel transport system for optical transport network

This paper describes recent technical challenges and the progress toward the realization of the optical transport network (OTN) based on 43 Gb/s channel. We describe the new digital frame format "OTU3: Optical Channel Transport Unit 3," which is standardized in ITU-T for OTN, for the enhancement of the network management capability in the OTN based on 43-Gb/s channels. We first proposed 43-Gb/s/ch dense wavelength-division multiplexing (DWDM) dispersion-managed transmission system using carrier-suppressed return-to-zero (CS-RZ) format that has several attractive features; it advances the evolution of OTN into 100 GHz-spaced long-haul DWDM transport networks. The first wavelength-division multiplexing (WDM) field trials confirmed the superiority of CS-RZ format in the DWDM transmission performance for the first time. The first 1 Tb/s (25 /spl times/ 43 Gb/s) WDM field trial confirmed the excellent network management capability of OTU3 in future data-centric OTN using the newly developed 43-Gb/s OTN line-terminal prototype.     

40Gb/s光纤通信系统中不同码型传输特性的实验研究

在高速光纤通信系统中码型的选择是决定系统传输质量和光谱效率的主要因素。码型的选择和信道速率、信道波长间隔、光放大器的选择、光放大器放置间隔、光纤的类型、色散管理策略等各种因素密切相关。分析了非归零码（NRZ）、归零码（RZ）和载波抑制归零码（CSRZ）码型的产生方式及特点。采用单信道和掺铒光纤放大器（EDFA）放大方式对三种码型进行了40Gb/s的100kmG.652光纤通信传输实验。比较了三种码型的系统传输持性、最佳入纤功率和不同入纤功率下的功率代价：载波抑制归零码最佳入纤功率为9dBm，功率代价小于非归零码和归零码。结果表明，在相同的色散补偿条件下，载波抑制归零码比归零码和非归零码有更优的非线性容忍度。     

A novel mode-splitting detection scheme in 43-Gb/s CS- and DCS-RZ signal transmission

Sophistication of the transmission format for 40-Gb/s/ch WDM networks is indispensable. In long-haul transmission applications, the selection of transmission format should be a principal issue. Recently, we have proposed several transmission formats including carrier-suppressed return-to-zero (CS-RZ) and duo-binary-carrier-suppressed (DCS-RZ), in so doing addressing the issue of superior performance versus fiber nonlinearity and spectral efficiency. The special spectrum structure of these formats enables a novel mode-splitting detection scheme. The scheme realizes a variety of applications in 40-Gb/s/ch transmission; including expansion of dispersion tolerance, automatic dispersion compensation, and BER improvement. We achieved 1.6 times. expansion of dispersion tolerance of 43-Gb/s DCS-RZ signals by introducing mode-splitting in the receiver. By applying the mode-splitting scheme for CS-RZ signals, we also demonstrated precise chromatic dispersion measurement with its sign detection without the need for any dithering operation and its application to automatic dispersion compensation at 43-Gb/s CS-RZ transmission.     

40Gb/s光DQPSK传输系统性能分析

介绍了光差分正交相移键控(DQPSK)的调制和解调方式,对非归零码(NRZ),归零码(RZ)和载波抑制归零码(CSRZ)进行调制,研究40Gb/s高速传输系统中不同类型的光信号.使用色散补偿方式进行200km的模拟仿真,比较不同码型的传输特性.分析表明CS-RZ-DQPSK调制格式,具有更强的抗色散和偏振模色散能力,在较宽的入纤功率范围内取得最小的眼图张开代价.     

1.6 Tbit/s(40×40 Gbit/s)光通信传输系统

在国家自然科学基金网(NSFCNet)上已实现由400 km×10 Gbit/s传输链路直接升级的一路400 km×40 Gbit/s光传输实验的基础上,采用自行研制的40×40 Gbit/s载波抑制归零(CS-RZ)码多波长光发送源,进行了160 km的1.6 Tbit/s(40×40 Gbit/s)波分复用(WDM)光传输实验。实验结果表明,对于常规中短距离10 Gbit/s传输链路可以直接升级至40 Gbit/s。但是由于40 Gbit/s传输系统的色散容限小于60 ps/nm,而且传输光纤与色散补偿模块的色散斜率不匹配,要实现40通道40 Gbit/s的传输,必须对40个信道分别进行精细的色散补偿。这也说明,对于宽带的40 Gbit/s多波长系统,有必要优化设计或更新传输链路。     

40Gb/s DWDM传送技术及实际考虑

给出了40Gb/sDWDM传送系统的进展现状,分析了40Gb/s传输问题和一系列使能技术,讨论了40Gb/sDWDM传送系统基本结构,并从实际应用的角度,对10Gb/s和40Gb/s传输系统的特性及成本进行了比较,最后指出了发展40Gb/s传送系统思路及对策。     

Polarisation-channel-interleaved CS-RZ transmission at 40Gbit/swith 0.8bit/s/Hz spectral efficiency

Experimental results are reported of polarisation-channel-interleaved carrier-suppressed RZ (PCI CS-RZ) ETDM/DWDM transmission of 8 × 40 Gbit/s over 320 km (2 × 160 kin) NDSF, with 0.8 bit/s/Hz spectral efficiency. An average system linear Q of 6.5 at a PRBS pattern length of 2³¹ - 1 and tolerance to at least 50% degradation in orthogonality are demonstrated     

All-Optical Format Conversions Using Periodically Poled Lithium Niobate Waveguides

We investigate all-optical format conversions by using cascaded second-order nonlinearities in periodically poled lithium niobate (PPLN) waveguides. Analytical solutions under non-depletion approximation with clear physical insights are derived, showing operation principles of various PPLN-based format conversions. We propose and theoretically demonstrate all-optical 40 Gb/s nonreturn-to-zero (NRZ) to carrier-suppressed return-to-zero (CSRZ), nonreturn-to-zero differential phase-shift keying (NRZ-DPSK) to return-to-zero differential phase-shift keying (RZ-DPSK), and NRZ-DPSK to carrier-suppressed return-to-zero differential phase-shift keying (CSRZ-DPSK) format conversions based on cascaded sum- and difference-frequency generation (cSFG/DFG). Tunable all-optical 20 Gb/s NRZ to return-to-zero (RZ) format conversion based on cascaded second-harmonic generation and difference-frequency generation (cSHG/DFG) is successfully confirmed in the experiment by setting NRZ signal at SHG quasi-phase matching (QPM) wavelength. Moreover, we experimentally report for the first time, PPLN-based all-optical 40 Gb/s NRZ-to-CSRZ, NRZ-to-RZ, and NRZ-DPSK-to-RZ-DPSK format conversions.