光端机、中继器的时钟提取和识别判决电路

本文分析了光纤数字系统中定时提取和识别判决电路的组成,给出选择和设计电路的依椐。并例举34Mb/s光端机和中继器中使用的具体电路。     

用1.55μm脊形波导C~3激光器的101公里1Gbit/s单模光纤传输实验

本文报导利用1.55μm单纵模解理耦合腔(C~3)脊形波导激光器,首次以500Mbit/s以上速率进行光波传输实验的结果。我们在101公里长的单模光纤上实现了1Gbit/s、误码率<2×10~(-10)的数字传输,创造了500Mbit/s以上无中继传输的纪录。同时还观察到了误码率最低限的证据,估计是由于残余分配噪声所致。但使用同样的C~3激光器在84公里1Gbit/s的实验中却未观察到上述情况。     

构成正交相移键控系统的超声方法

我们用声表面波(SAW)器件研制成正交相移键控系统。一种有两个或三个叉指换能器(IDT)的SAW延迟器件可以作为通讯系统的调制和解调的键控元件。在发射系统中,应用有不同超声相位延迟的四根延迟线产生对应于一个输入四进制脉冲串的四相相移键控射频(RF)信号。在解调部分,为了同步,配置了一个附加的IDT。在这种情况下,当载频为50MHz时,数字传输速度是0.1Mbit/s。     

274Mbit/s和420Mbit/s通过101km和84km单模光纤的传输实验

为不同的目的用274Mbit/s和420Mbit/s完成了四个1.3μm低损耗单模光纤的传输实验。第一个实验是证明274Mbit/s通过101km单模光纤的传输,其色散代价可以忽略。第二个实验是274Mbit/s和84km,只使用了适合于海下光缆系统的元件。两个附加实验都是420Mbit/s,用84km的光纤时达到35GHz比特速率×距离的乘积,并表明63km无色散代价和色散为2.4ps/km·nm。     

400Mbit/s光发射机模型

一、引言根据国际上光纤通信的发展趋势,我们对400 Mbit/s单模光纤传输系统进行了研究,并全部采用国产器件制造出了系统性能样机,从而在国内首次成功地实现了1.3μm波长、400 Mbit/s、30km无中继单模光纤的传输。本系统采用单模激光器(波长为1.3μm)作为系统光源,Ge-APD作探测器;无中继光纤长度为30 km;接收机灵敏度为-32 dBm(BER<10~(-9))。本文主要介绍光发射机部分的性能、特点和电路结构。     

有关图象数字传输方式的建议

本文根据国内外图象数字传输的研究和开发情况,对我国即将建立的数字通信网路中几种图象信号的数字传输方式提出建议。对彩色电视,建议研究和开发高质量的68Mbit/s码率方式和一般质量的34Mbit/s码率方式;对会议电视,建议和欧洲七国合作的COST计划协调一致;对于凝固图象电话会议,由于可以在现有模拟通信电话信道中以2.4～4.8～9.6kbit/s数传码率传送,建议尽快开发,以满足当前需要;对于可视电话,建议对64kbit/s码率系统进行研究。     

长途传输低速率电路开通方式的改进与传输网的智能化改造

本文通过对长途传输机房在2 Mbit/s、10 Mbit/s、100Mbit/s等低速率电路业务开通中一些问题的分析,结合现代传输网络向ASON(自动交换光网络)演进的发展趋势,提出了一种全面简化电路开通的改进方案,可大大提高电路安全性以及带宽利用率和设备端口利用率,同时有利于实现今后向ASON的平稳演进.     

光电快速以太网转换器AL210

AL210是ALLAYER公司设计的用于在100Mbit/s光纤与双绞线之间进行快速太网转换的芯片，利用它可以实现光纤和双绞线之间信息的相互转换，以提高网络速度。文中介绍了AL210的特点、功能及其引脚，最后给出了它的典型应用电路。     

基于CCITT SDH标准的同步数字传输系统

NTT电信网的数字化是从1965年引入PCM—24 1.5Mb/s数字传输系统开始的,随着数字同轴电缆传输系统如DC—400M系统和数字无线电系统如20L—P1系统的应用,70年代继续进行网络数字化,80年代又引入了光纤传输系统如F—1.6G系统。从70年代中期开始,采用6.3Mb/s同步数字终端系统如M20系统和数字交换系统,实际上已建成了数字网。特别是光纤和数字无线电系统不断使传输成本得到大幅度下降。     

565Mb/s光纤数字传输系统工程设计问题的探讨

一、概述 目前,我国光通信事业发展迅速,已经建成或即将建成大量的140Mb/s光纤数字传输系统。但随着我国通信事业的迅猛发展,势必需要建设更高速率的光纤数宇传输系统,可供选择的建设方案有很多,本文仅就565Mb/s光纤数字传输系统设计的有关问题作一些探讨。     

Optical Fiber System Applications Aspects in Future NTT Networks

This paper describes some aspects of optical fiber cable system applications in future NTT transmission networks, considering voice transmission as predominant even in future transmission networks in accordance with demand forecasts. The desirable optical fiber cable transmission system which should be developed and introduced is discussed taking into account optical fiber costs, demand estimates, pertinent technological developments, etc. It was concluded that the following process of introducing optical fiber cable transmission systems should be feasible. In the first step, approximately 32 Mbit/s and 100 Mbit/s digital transmission systems should be employed for short and medium haul trunks with heavy traffic using graded index optical fibers. A large capacity, long haul digital transmission system, such as a 400 Mbit/s system using graded index or, if possible, single mode optical fiber should be introduced next. The optical fiber cable costs at which fiber systems become economical, depend upon the application area. For short and medium haul systems, 40¢ per meter per core is required, but $2 per meter per core is sufficient for large capacity, long haul systems. For a short haul system operating at approximately 1.5 Mbits/s or 6 Mbits/s, the advantages of its introduction greatly depend on optical fiber costs which should be less than 20¢per meter per core.     

Optical Pulse Formats for Fiber Optic Digital Communications

Some new optical pulse formats are investigated for solving practical problems in fiber optic communication systems. These pulse formats provide many advantageous features such as error monitoring capability, abundant timing information, uniform optical power utilization, stable detection of optical input, and so forth. It is shown that a modification of Personick's receiver design theory can be used for comparison of various optical pulse formats. The comparison suggests that for state-of-the-art fiber systems with moderate fiber loss and moderate repeater spacing, where no pulse equalization is required, some new classes of 1 binary digit converted to 2 binary digits (1B2B) or 2B3B formats will permit the realization of very simple and reliable repeaters for fiber optic digital transmission. A future low-loss fiber system may permit a very long repeater spacing with the help of equalization. In this case, application of the correlative signal-processing technique is shown to be very promising. Experimental 6.3 Mbit/s and 100 Mbit/s transmissions demonstrate some advantageous features of these optical pulse formats.     

Discrete Multitone Modulation for Maximizing Transmission Rate in Step-Index Plastic Optical Fibers

The use of standard 1-mm core-diameter step-index plastic optical fiber (SI-POF) has so far been mainly limited to distances of up to 100 m and bit-rates in the order of 100 Mbit/s. By use of digital signal processing, transmission performance of such optical links can be improved. Among the different technical solutions proposed, a promising one is based on the use of discrete multitone (DMT) modulation, directly applied to intensity-modulated, direct detection (IM/DD) SI-POF links. This paper presents an overview of DMT over SI-POF and demonstrates how DMT can be used to improve transmission rate in such IM/DD systems. The achievable capacity of an SI-POF channel is first analyzed theoretically and then validated by experimental results. Additionally, first experimental demonstrations of a real-time DMT over SI-POF system are presented and discussed.      

A Simulation Study on Clock Recovery of a Minimum Bandwidth Signal

Jitter and BER performance of non-linear clock recovery circuits are evaluated for a minimum bandwidth signal. To investigate the effect of bandwidth in optical transmission, BER performance of MB810 and NRZ signals with various types of timing recovery circuits are compared for a 40 Gbit/s optical link. Among the systems adopting non-linear timing recovery circuits, the MB810 signal employing an absolute value rectifier shows superior performance. We show that timing recovery without a non-linear circuit is also possible, and compare its BER performance with that of the others. Jitter performance of the fourth-law rectifier and that of the absolute-value rectifier is made for a minimum bandwidth signal. The mathematical derivation of the timing wave is also carried out for the clock recovery of the fourth-law rectifier. The result shows that the derived timing wave is expressed as a function of a pulse shape entering the timing path and the band-pass filter tuned to the pulse repetition rate.     

Design of integrated services digital broadcasting systems usingmultirate optical fiber code-division multiplexing

This paper presents the design of a new type of integrated services digital broadcasting (ISDB) systems which use a multirate optical fiber code-division multiplexing (OF-CDM) technique. The proposed system can efficiently multiplex various kinds of digital signals with multiple bit rates. This is feasibly achieved by using strict optical orthogonal codes of both auto- and cross-correlation constraints being “1” in multirate OF-CDM systems. Moreover, the low-cost design of OF-CDM transmitters is presented, and experimental demonstrations are also carried out. The measured results show that a transmission distance up to 13 km can be feasibly accomplished by using the proposed transmitter design and the external optical injection-locking scheme. It is expected that the proposed ISDB systems can be employed to cost-effectively transmit fast ethernet (125 Mbit/s), FDDI (125 Mbit/s), ATM (155 Mbit/s), and ESCON (200 Mbit/s) protocol data. Their potential applications include Internet services and multimedia broadcasting, such as videoconferencing, video on demand, HDTV, distance learning, and World Wide Web     

Trends in long-wavelength single-mode transmission systems and demonstrations in japan

Long-wavelength single-mode optical fiber transmission technology has recently made rapid progress and is now moving into the commercial operation stage. This paper describes the present state of this technology focusing on the research and development work in the Electrical Communication Laboratories. Based on the results of experiments on optical devices and on preliminary system feasibility analysis, it is shown that, at the present time, an optical wavelength in the 1.3 μm band is desirable for large capacity transmission from the viewpoint of attainable repeater spacings. A field trial plan of a 400 Mbit/s optical transmission system for a long-haul trunk which can compete economically with existing digital transmission systems is outlined.     

A High-Reliability 565 Mbit/s Trunk Transmission System

A high-reliability 565 Mbit/s trunk transmission system capable of operating over a 25.5 dB fiber section loss at 1.3 μm is described. Details of the line terminal and repeater design are presented, together with an outline of the integrated circuit design and process. Aspects of the line code and interface choice are also discussed in relation to the optical receiver, transmitter, and supervisory circuits. Finally, systems design aspects are considered and field experience resulting from a system installation spanning 77 km between Birmingham and Derby is reported.     

Optical Fiber System Trials at 8 Mbits/s and 140 Mbits/s

This paper describes an optical fiber system developed at the British Post Office (BPO) Research Centre, Martlesham Heath, which provides telephone circuits in an 8 Mbit/s junction between the Centre and Ipswich Telephone Exchange via 13 km of BICC cable incorporating Corning fibers. In parallel, a 140 Mbit/s system operating over 8 km of cable has been demonstrated. The systems were constructed in accordance with standard BPO equipment practice and the cables were installed by local area staff in existing ducts.     

Long-span single-mode fiber transmission characteristics in long wavelength regions

Experimental and analytical results on high-speed optical pulse transmission characteristics for long-span single-mode fibers by using InGaAsP lasers, emitting at 1.1, 1.3, and 1.5 μm, as well as a Ge-APD are reported. At 1.1 μm, 400 Mbit/s transmission experiments were successfully carried out with 20 km repeater spacing. At 1.3 μm, where single-mode fiber dispersions approach zero, error rate characteristics showed that optical power penalties at 100 Mbits/s and 1.2 Gbits/s are negligible even after 30 and 23 km fiber transmission, respectively. It was confirmed that a 1.6 Gbit/s transmission system has 15 km repeater spacing. At 1.5 μm, where silica fibers have ultimately minimum loss, single-mode fiber transmission experiments were carried out at 100 Mbits/s with about 30 km repeater spacing. 400 Mbit/s transmission characteristics using 20 km fibers were also studied. Fiber bandwidths, measured by optical pulse broadenings after 20 km transmission, were 24, 140, and 37 GHz . km . nm at 1.1, 1.3, and 1.5 μm, respectively. Progress in lasers, fibers, and optical delay equalizers at 1.5μm will bring about large-capacity transmission systems having about 150 km repeater spacing. These results reveal fiber dispersion characteristics in the long wavelength region essential to high data rate single-mode fiber transmission system design.