Signal linewidth broadening due to nonlinear Kerr effect inlong-haul coherent systems using cascaded optical amplifiers

Signal spectral linewidth broadening due to the interaction between nonlinear Kerr effect and spontaneous emission from optical amplifiers in long-haul coherent optical fiber communication systems using optical amplifiers is examined theoretically and experimentally. By theoretical consideration and recirculating-loop experiments, it is shown that this effect becomes an essential limitation on maximum transmission length in transoceanic coherent optical fiber submarine cable systems     

Optical amplifiers transform long-distance lightwavetelecommunications

Optical amplifiers and wavelength-multiplexing technology are transforming lightwave communications by providing cost-effective upgrades that will increase immensely the transmission capacity of long-distance telecommunications networks. A new generation of undersea cable systems using fiber optical amplifiers as repeaters has been developed for transoceanic applications, yielding a capacity almost ten times larger than conventional systems using opto-electronic regenerators. Terrestrial long-haul networks will benefit significantly from amplified wavelength-multiplexed transmission systems designed to access the large inherent bandwidth in the installed fiber. Successful deployment of these advanced systems requires a thorough understanding of optical amplifiers and the optical fiber medium, as their requirements interrelate through optical bandwidth, noise, dispersion, optical nonlinearities, and their impact on signal transmission. While the first commercial WDM amplified lightwave systems are deployed for point-to-point applications, optical transparency and wavelength multiplexing will be exploited for networking leading to the higher functionality and improved cost-effectiveness expected of photonic networks     

海底光通信市场近况

跨洋海底光通信是海底光通信市场的主体,目前的跨洋海底光缆都是使用光放大器的系统,并已发展到了第3代。跨大西洋和跨太平洋的海底光通信仍为此类市场的主导,但原来海底光通信并不发达的地区如亚太、非洲和拉丁美洲近来也呈现出蓬勃发展的迹象。     

Optical undersea cable systems trends

This paper reviews the evolution of undersea cable technology from the telegraph cables of the mid-nineteenth century to the optical undersea cables of today. Future systems will use optical fiber amplifiers which offer significant technical and economic advantages. Consequently, emphasis is placed on problems associated with the accumulation of small, second-order effects in long lengths of optical fiber and, specifically, their impact on the 5-Gb/s optically amplified transoceanic undersea systems scheduled to be deployed in 1995. Technology options for achieving further capacity increases, among them the use of optical solitons, and trends toward networked undersea cable systems with automatic restoration features are described     

Broadband: the last mile

The regulatory and service drivers that are prerequisites for local access evolution to the broadband integrated services digital networks are discussed. A tutorial on the state of the art in relevant technologies is presented, and it is shown that many of the technologies are not yet mature. The broadband technologies discussed are analog cable television systems, optical fiber, optical amplifiers, optical receivers, transceivers, and image compression systems. Regulatory considerations include bandwidth on demand and competition     

Polarization dependent distortion in AM-SCM video transmissionsystems

The second-order intermodulation distortion product, namely composite second-order (CSO) distortion, of an AM-SCM video transmission system can be caused by the optical isolators, cascaded fiber amplifiers, or the fiber transmission cable employed. Moreover, the absolute distortion value depends on the polarization angle of light input to the optical isolators, cascaded fiber amplifiers, and fiber transmission line. The degraded distortion values are measured and their mechanisms are clarified     

Performance monitoring of long chains of optical amplifiers

The monitoring and fault location of long chains of optical amplifiers such as will be deployed in undersea cable systems is an important design consideration. The Letter describes two methods which have been proposed and one which has been evaluated on the authors' test bed simulator of 3100 km with OAs spaced at 45 km and operating at 5 Gbit/s.<>     

Nonlinear Liqued Crystal Optical Signal Amplifiers

The principle,structure and system of nonlinear liquid crystal optical sig-nal amplifiers are described.Experimental results are theoretically analysed for optical signal amplifers.It shows that this type of the optical signal amplifiers are comprised of liquid crystal light sensitive medium which can receive a modulated signal optic wave and a pump wave,and can be applied to optical transmission systems.     

Nonlinear Liquid Crystal Optical Signal Amplifiers

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Optical fibers and amplifiers for WDM systems

The development of optical-fiber amplifiers allowed a dramatic increase in the capacity of optical transmission systems while reducing system costs. Capacity increases are possible because the high output powers afforded by optical-fiber amplifiers support higher bit rates, while their broad bandwidth and slow gain dynamics allow multichannel operation. This benefit comes at the expense of having to manage signal-to-noise ratio degradations due to the accumulation of amplifier noise and dispersion distortions accumulated over the total system link. Furthermore, nonlinear optical effects become significant with the use of high power signals over long lengths of fiber, causing cross talk among the different channels and increasing signal distortions. To fully exploit the potential capacity of wavelength division multiplexing systems, the optical characteristics of the fibers and optical-fiber amplifiers must be optimized. The optical amplifiers should have low noise and flat gain, which can be achieved by using 980-nm pump lasers, optimized fiber glass composition, and gain-flattening filters. The optical fibers should have a small nonzero dispersion and large effective area. Both features can be achieved by optimizing the fiber index profile. This paper summarizes the state of the art in these components and points to directions for future exploration     

Power penalties due to multiple Rayleigh backscattering in coherenttransmission systems using in-line optical amplifiers

The power penalties due to double Rayleigh backscattering are calculated for coherent lightwave systems with optical in-line amplifiers. It is shown that coherent systems are less sensitive to Rayleigh noise than high-speed direct-detection systems. For PSK heterodyne systems, the maximum gain of in-line amplifiers that can be achieved without optical isolation is limited to about 25 dB     

Intermodulation Noise and Products Due to Frequency-Dependent Nonlinearities in CATV Systems

The noise power spectral density and sinusoidal response at the output of analog coaxial cable lines having amplifiers with frequency-dependent nonlinear characteristics are derived. Their use for the design and optimization of coaxial cable systems for TV transmission is demonstrated. Tables are given from which the levels of the intermodulation products for conventional 12- and 30-channel video systems can be readily obtained.     

Effect of span loss increase on the optically amplifiedcommunication system

In optical fiber communication systems using Er³⁺ doped fiber amplifiers operating in their compression region, the optical signal power is known to be restored by the self-healing effect in the case of the span loss increase. In this paper, the influence of such excess loss on the system transmission performance is experimentally and numerically investigated from the point of view of the system signal-to-noise ratio and Q-factor. The results show that the system SNR is not completely recovered although the signal power is restored after several stages of amplifiers and that there exists the residual degradation of the system SNR. Through a 5.3 Gb/s data transmission experiment over 3000 km, the transmission penalty due to the excess span loss is confirmed to be decided by this residual degradation of the system SNR. The obtained results can be used for system design and a plan of maintenance for the optical amplifier communication system     

Semiconductor laser optical amplifiers for multichannel coherentoptical transmission

The application of semiconductor laser optical amplifiers in multichannel coherent optical transmission systems is investigated. The amplifiers considered (λ=1.3 μm) exhibit a gain of 24 dB at a grain ripple <2 dB and a 3-dB bandwidth of about 4000 GHz. The characteristics of these amplifiers and transmission experiments with these amplifiers are described. The investigations concern noise accumulation in an amplifier chain, generation of echoes due to backward gain in cascaded amplifiers, crosstalk in multichannel transmission, and the effect of gain saturation due to spontaneous emission. A good fit is shown between the advantages of multichannel coherent optical transmission systems and the properties of semiconductor laser optical amplifiers, which are very promising for future long-haul optical transmission systems     

Optical-transmission characteristics of optical-fiber cables and installed optical-fiber cable networks for WDM systems

Many cables containing 1.3-/spl mu/m zero-dispersion single-mode (SM) optical fibers are installed in trunk and access networks. Recently, there have been a number of studies on wavelength-division-multiplexing (WDM) systems designed to increase transmission capacity and flexibility. If we can construct WDM systems using SM optical-fiber cable networks designed to transmit using wavelengths in the 1.3-/spl mu/m window (O-band), this will prove very effective in reducing construction costs. It is therefore important to examine the wavelength dependence of the transmission characteristics of SM optical-fiber cables and networks that have already been installed and in which several optical fibers are joined. In this paper, we describe the measured optical characteristics of SM optical-fiber cables and installed optical-fiber cable networks at various wavelengths. The optical characteristics were stable in the 1.46 to 1.625-/spl mu/m wavelength range and we confirmed that the installed SM optical-fiber cable networks could be used for WDM system applications.     

宽带增益平坦光纤Raman放大器的研究进展

宽带增益平坦光放大器是密集波分复用光通信系统提高信息容量的基本需求。在总结宽带掺铒光纤放大器的基础上 ,介绍了展宽光纤Raman放大器平坦增益带宽的基本方法和研究现状。     

On AGC transient-response behavior in cascaded amplifiers

Automatic gain control (AGC) in systems of cascaded amplifiers is examined by transient-analysis methods. When many identical amplifiers with AGC are cascaded as in cable TV and other communications systems, transient response computations show progressive deterioration of AGC performance with increasing cascade length.     

Optical time domain reflectometry on optical amplifier systems

The use of optical time-domain reflectometry (OTDR) on long-span fiber transmission systems containing in-line optical amplifiers is discussed. Having identified the specific requirements for OTDR equipment, measurements were carried out on systems of up to 300 km in length, containing three semiconductor laser amplifiers. The results demonstrate that OTDR can be used not only for fault location on fiber links several hundred kilometers in length but also as an alternative to standard system supervisory techniques, thus providing the potential for minimizing the hardware in the optical amplifier stages of future long-span fiber optic transmission systems     

Limitations to and solutions for optical loss in optical backplanes

In this paper, recent literature on the discussion on high-speed backplanes with optical, electrical, and mixed solutions, as well as on polymer-waveguide systems suitable for implementation on printed circuit boards (PCBs), is reviewed from the point of view of their optical losses. The reevaluation of the optical power budget for realistic high-speed optical polymer-waveguide links on backplanes showed that signal amplification is necessary to boost the signal, which resulted in an additional literature review on advances in optical amplifiers based on silicon bench technology available. Finally, a concept study of an active optical waveguide amplifier device, based on planar optical waveguide amplifiers and semiconductor optical amplifiers, was performed. The amplification device can be flip-chip mounted on the backplane to compensate for optical losses due to signal routing, which increases the overall degree of freedom in waveguide routing on high-density interconnects for backplanes. The hybrid concept design guarantees compatibility with the processes of the PCB industry.     

1550nm光纤放大器在广电网络中的应用与维护

为了解决有线电视信号的超长距离光纤传输,1 550 nm掺铒光纤放大器是1 550 nm光纤通信系统中重要的光中继传输设备,主要用于电视图像信号、数字电视信号、电话语音信号和数据(或压缩数据)的传输,实现一省一网、以地市州为中心的网络传输体系,1 550 nm光纤放大器的光路结构在功能上包括光放大单元、隔离单元以及监控单元,其中光放大单元采用980 nm或1 480 nm泵浦激光器,用1 550 nm光探测器进行输入输出光的监控,在光放大单元的前后加入光隔离单元以抑制振荡提高性能。