光通信技术新动向

有消息报道 ,最近有关科研人员将光通信技术向前推进了一步。系统方面Nortel Technologies公司将推出 DWDM通信系统的主要内容。据称 ,每个波长的数据传输速度达到80 Gb/ s。在 SONET/ SDH系统中 ,将传输速度依次提高为 6 2 2 Mb/ s、2 .5Gb/ s、10 Gb/ s、4 0 Gb/ s,也即传输速度依次提高了 4倍。NEC开发出了 DWDM传输装置“Spectral Wave16 0”并将于 2 0 0 0年第四季度出厂。该装置能将传输速度为 10 Gb/ s(OC- 192 )的光信号重叠为 16 0波束 ,通过一根单模光纤进行传输 ,通信容量达到了 1.6 Tb/ s。NEC此次开发的 DWDM…     

光纤链路色散对光纤传输网络设计的影响讨论

光纤链路色使得DWDM系统从10Gb/s升级到40Gb/s后变得更加困难。特别是在DWDM系统或UDWDM系统中,光纤链路的色散对于传输系统的调制技术和色散补偿技术等的选择尤为重要。文章通过对光纤链路积累的残余色散大小进行对比,并结合现运行的40Gb/s DWDM系统技术要求,分析了不同调制技术下光纤链路色散对工程设计的技术要求,得出静态和动态相结合的色散补偿方案。     

基于集中式OFC的DWDM光纤无线接入系统

提出了一个千兆容量的光纤无线系统,该系统通过使用一个集中式光学频率梳(optical frequency comb,OFC),能够应用于高速无线网和密集波分复用(DWDM)接入网之间,每个DWDM用户可以同时获得有线和无线服务,通过该系统传输速率为2.5Gb/s的信号,成功实现了在有线25km单模光纤和6m无线60GHz频段的信号传输,系统传输误码率低于2×10-3。     

长距离DWDM系统中EDFA的研制

采用光纤光栅和增益平衡器等光无源器件 ,在常规掺铒光纤放大器 ( EDFA)内部引起光反馈和滤波整形机制 ,研制成功多信道动态增益均衡 EDFA,锁定工作波长带宽 17nm( 1544～1561nm) ,在输入功率 - 2 0～ - 5d Bm内增益恒定为 2 3d B,噪声系数小于 5d B,输出功率 18d Bm,并进行了 80 0 km× 8× 2 .5Gb/ s长距离 DWDM信号高速传输的实验研究 ,在信道数改变的动态运行情况下 ,系统误码率达 10 -10 。     

电吸收调制器特性研究

针对电吸收调制器在光纤无线通信系统中的重要作用,分析了电吸收调制器的插入损耗和由电吸收调制器组成的光纤无线通信系统的误码率和噪声系数。发现在波长从1530~1570nm范围内插入损耗都比较小;在工作波长为1550nm的通信系统内实现了速率为2.5Gb/s信号在200km长度的标准光纤内传输。系统功率衰减很小,在选择合适的匹配阻抗下,通信系统噪声系数能够达到12dB左右。     

色散补偿及EDFA增益均衡的一体化

提出一种新的色散补偿及EDFA增益均衡的一体化方法。在10Gb／s的光通信系统和600km G652光纤中首次实现了基于16个碉啾光纤布拉格光栅(FBG)的色散补偿及掺饵光纤放大器(EDFA)的增益均衡。16个FBG的波长间隔为1．6nm，波长覆盖C波段1529～1556nm约27nm的范围。经600km G652光纤传输后，10Gb／s的NRZ码传输功率代价小于2dB。     

国内光通信技术的最新展望

超高速率、超大容量、超长距离技术研究进展较快 目前,核心网中的主流设备是基于10Gb/s的DWDM,基于40Gb/s的DWDM(Dense Wavelength Division Multiplexing,密集波分复用)设备和系统已经在国内外开始小规模商用,基于100Gb/s的DWDM系统在国外已建设了试验工程,国内主要处于测试验证阶段.为了适应基于超级通道( Supper Channel)在DWDM中的应用,相关的灵括栅格技术正在开展研究.为适应分组传送的PTN技术已经在网上大规模应用;分组OTN技术正在开发中.     

高速光传输中双二进制调制解调系统

提出一种利用逻辑器件搭建的高速双二进制调制(Duo-Binary Modulation,DBM)系统,简述了双二进制调制理论并介绍了新的平台设计方案,实现了在25km标准单模光纤上实时传输速率为10.3125Gb/s的光信号.实验中采用高速误码仪进行检测,实验结果表明,该系统在离线时能实现零误码,在接收光功率为-10dBm时误码率小于10-7.     

基于铒镱共掺光纤放大器的仿真研究

基于铒镱掺杂光纤放大器具有光纤短增益特性好的优点,对在混合光纤放大器中用铒镱掺杂光纤放大器来代替掺铒光纤放大器的方法进行了研究,并对铒镱光纤的长度和掺杂浓度进行了精心的选择,而后利用仿真软件对在2.5Gb/s和10Gb/s速率下的混合光纤放大的DWDM系统进行了仿真分析.     

高带宽单模光纤

一项可提高标准单模光纤波分复用(WDM)系统传输容量的技术可能会影响大多数现已使用的光纤网络.来自意大利米兰的Pirelli Cables and Systems公司和纽约Red bank的AT＆T Labs的研究者们在75km长的单模光纤上演示的4个信道均以40Gb/s的速率进行WDM传输的实验.他们还把320Gb/s速率信号通过32个10Gb/S的速率通道传输375km.这些实验更为重要的是,有可能使用光纤光栅使一个波长的信号以40Gb/s的速率传输.(NO.38)     

Effects of nonlinear dispersion in EDFA's on optical communicationsystems

The signal-induced change of the refractive index in an erbium-doped fiber amplifier (EDFA) causes a phase modulation imposed on a signal when passing the EDFA. In this paper, we apply our extended EDFA model on an optical communication system. The model includes this phase modulation, by including the nonlinear dispersion in an EDFA, and the spontaneous emission noise. The influence of these effects on an optical communication system is examined by means of Q-factor and eye diagram. We assume an intensity modulated-direct detection (IM-DD) system operating at 193 THz (1552.5 nm) with a bit rate of 10 Gb/s in the anomalous dispersion regime and a total fiber length of 500 km. The fibers are assumed to be dispersion shifted ones, EDFAs are used to compensate for the fiber loss. By numerical simulation we obtain results for the influence of the phase modulation (nonlinear dispersion) due to the signal induced change of the refractive index in an EDFA and the spontaneous emission noise at different input peak powers. Neglecting the signal-induced change of the refractive index strongly underestimates the Q-factor in the anomalous dispersion regime. Therefore it should be included for reliable system simulations. This can be done with the numerical model presented here     

外调制光发射模块

介绍2.5Gb/s外调制DWDM光发射模块设计及性能测试情况.文中LiNbO3外调制光发射模块用于32波长(100GHz间隔)的DWDM传输,可传输640km.该外调制模块包括控制模块和调制模块,它同其他SDH、DWDM光模块相比,在具有光功率监测、光功率告警和温度告警功能的同时,增加了激光器驱动电流监测、制冷电流监测、激光器管芯温度监测、波长控制功能等.外调制模块比其它方式的光发射模块具有色散性能好、传送距离远(与EDFA配合)等优点.外调制模块进行了温度实验,模块波长控制能力和光功率控制能力均达到传输系统要求,并且通过使用EDFA进行了400km、680km传输,获得了满意的结果.     

Performance comparison of an 80-km-per-span EDFA system and a 160-km hut-skipped all-Raman system over standard single-mode fiber

In this paper, we present a comprehensive comparison of the performance of an 80-km-per-span erbium-doped fiber amplifier (EDFA) system and a hut-skipped (160-km-per-span) all-Raman system over standard single-mode fiber (SSMF) for the first time, using semianalytic models. The numerical results reveal that a hut-skipped all-Raman system (using one-order Raman pumping) can achieve comparable performance as the conventional 80-km-per-span EDFA system for a common 50-GHz-spaced 80 /spl times/ 10 Gb/s nonreturn-to-zero (NRZ) wavelength division multiplexing (WDM) system at typical fiber loss of 0.22 dB/km. For 100-GHz-spaced 40 /spl times/ 40 Gb/s carrier-suppressed return-to-zero (CS-RZ) WDM transmission, it was found that a hut-skipped all-Raman system can achieve even better performance than the current 80-km-per-span EDFA system. It was also found that the impact of pattern-dependent Raman crosstalk is more severe than interchannel cross-phase modulation (XPM) in a hut-skipped all-Raman system with 80 /spl times/ 10 Gb/s capacity.     

High performance selectively oxidized VCSELs and arrays forparallel high-speed optical interconnects

High-bandwidth single-mode selectively oxidized vertical-cavity surface-emitting laser (VCSEL) arrays operate at 980 nm or 850 nm emission wavelength for substrate or epitaxial side emission. Coplanar feeding lines and polyimide passivation are used to reduce electrical parasitics in top-emitting GaAs and bottom-emitting InGaAs VCSELs. To enhance fundamental single-mode emission for larger devices of reduced series resistance a surface relief transverse mode filter is employed. Fabricated VCSELs are applied in various interconnect schemes. InGaAs quantum-well based VCSELs at 935 nm emission wavelength are investigated for use in perfluorinated graded-index plastic-optical fiber (GI-POF) links. We obtain a 7 Gb/s pseudo random bit sequence (PRBS) nonreturn-to-zero (NRZ) data transmission over 80 m long 155 μm diameter GI-POF. We investigate data transmission over standard 1300 nm, 9 μm core diameter single-mode fiber with selectively oxidized single-mode GaAs and InGaAs VCSELs. We achieve biased 3 Gb/s and bias-free 1 Gb/s pseudo-random data transmission over 4.3 km at 830 nm emission wavelength where a simple fiber mode filter is used to suppress intermodal dispersion caused by the second order fiber mode. For the first time, we demonstrate 12.5 Gb/s data rate transmission of PRBS signals over 100 m graded-index multimode fiber or 1 km single-mode fiber using high performance single-mode GaAs VCSELs of 12.3 GHz modulation bandwidth emitting at λ=850 nm     

Transmission of 160-Gb/s Modified Manchester modulation over WDM system

The paper examines the performance of Modified Manchester (MM) modulation scheme over wavelength division multiplexing (WDM) in high-speed optical communication links. The MM as a new modulation technique has a narrow spectral width compared to conventional Manchester coding, which allows its implementation in WDM systems beneficial. In this study, the performance characteristics of MM and conventional Manchester modulation formats are assessed in WDM system at 10 Gb/s bitrate for each channel, for the least allowable channel spacing as well as tolerance to chromatic dispersion (CD). It is revealed from the results of simulation that MM performs meaningfully well in comparison with conventional Manchester in terms of tolerance against narrow optical filtering, spectral efficiency, which is improved by 32% and CD tolerance, which is improved by +100 ps/nm. Sixteen wavelength channels (16 × 10 Gb/s) are modulated to provide 160 Gb/s data capacity, which was transmitted successfully over 224 km standard single mode fibre (SSMF) using MM while the conventional Manchester only covered about 157 km.     

超高速光通信的新技术及应用

文章介绍了40 Gbit/s、100 Gbit/s及以上速率超高速光通信中将会用到的新技术,包括相位调制、正交幅度调制、多电平调制等新型调制技术;偏振复用和正交频分复用这两种新型复用技术;相干接收技术原理、优点和应用必要性;光子集成技术的应用和技术发展。最后介绍了这些新技术在400 Gbit/和1 Tbit/s等超高速光通信上的应用。     

8 × 10 Gb/s transmission system over 2 015 km with dispersion compensation by fiber Bragg Grating

The cascaded chirp fiber Bragg gratings（CFBGs） with ITU-T standard wavelengths and wavelength grid are applied to compensate the dispersion of 8×10 Gb/s WDM system. The ASE of the EDFA could be reduced, the OSNR of the transmitted signal can be increased and the fluctuation of the EDFA gain can be restrained in a certain scope by the CFBG employed in the system. Experiment of error-free 8×10 Gb/s 2015 km transmission without FEC and electric regeneration is demonstrated in this paper. In this system, only EDFA is used as amplifier,and no other form of dispersion compensator is adopted except CFBG. The experimental result showed that after 2 015 km transmission,the consistency of the dispersion compensating for each channel is perfect.     

Communications performance of a multimode EDFA

We report an investigation of a multimode EDFA used as an optically preamplified receiver. A two-stage amplifier pumped at 982 nm shows gain of up to 40 dB at 1553 nm. We study the communications performance of the receiver at 10 Gb/s and compare it with theory. The measured sensitivity is 220 photons per bit at a bit error rate of 10/sup -9/ and data rate of 10 Gb/s. This is 4.5 dB from the quantum limit of 75 photons per bit for a 56 mode amplifier.     

量子密钥分发和经典光通信波分复用共纤传输研究

研究了量子密钥分发和经典光通信波分复用共纤传输的技术难点和可行性。基于系统重复频率 40 MHz的诱骗态相位编码BB84协议量子密钥分发设备,提出了3种量子信号与经典光信号的波分复用共纤传输方案：单纤双向CWDM共纤传输方案,复用1 550.12 nm波长量子信号、1 310 nm波长时钟信号以及正向1 590 nm波长100 Mbit/s速率光信号和反向1 610 nm波长100 Mbit/s速率光信号,光纤传输距离70 km下密钥成码率达到1.2 kbit/s;双纤双向CWDM共纤传输方案,复用1 550.12 nm波长量子信号、1 610 nm波长时钟信号以及1个波长的同向光信号在1 310 nm波长OOK光信号速率10 Gbit/s,光纤传输距离55 km下,密钥成码率达到1.58 kbit/s;双纤双向DWDM共纤传输方案,复用1 550.12 nm波长量子信号、1 610 nm波长时钟信号以及2个同向波长各自为1 551.72 nm和1 552.52 nm,并模拟100 Gbit/s相干光通信DP-QPSK信号接收功率,光纤传输距离70 km下,密钥成码率达到1.16 kbit/s。