Erbium-doped fiber amplifier cascade for multichannel coherentoptical transmission

The requirements and practicalities of amplifier cascades for multichannel coherent transmission are discussed. A four-amplifier cascade which maintains an overall noise figure of less than 13 dB across a 20-nm optical bandwidth for total input powers up to -10 dBm is described. A potential capacity of 100 wavelength division multiplexing channels is demonstrated in a 300-km 622-Mb/s DPSK (differential phase shift keying) coherent transmission experiment     

基于级联光纤环形镜的增益平坦掺铒光纤放大器

基于光纤环形镜的滤波原理,提出利用级联结构光纤环形镜(FLM)实现掺铒光纤放大器(EDFA)增益平坦滤波的方案,并进行了相关实验研究.实验结果显示,使用级联FLM取得了明显的增益平坦效果,其1535-1557nm波长范围内的增益不平坦度由±5dB减小到±1dB.     

Erbium-doped fiber amplifier with flattened gain spectrum

An optical notch filter was incorporated within the length of all erbium-doped fiber amplifier. Careful choice of the filter characteristics and location made it possible to enhance the amplifier gain at wavelengths around 1550 nm. An amplifier with 27-dB gain and 33-nm bandwidth was demonstrated. The saturation characteristics of the amplifier were uniform across its gain spectrum, making it ideal for wavelength division multiplexed (WDM) application.<>     

HFC系统用掺铒光纤放大器的设计与测试

介绍了光纤同轴电缆混合网（HFC）中应用的掺铒光纤放大器（EDFA）的工作机理和性能特点;论述了在研制HFC系统用掺铒光纤放大器时,为了提高其性能而应该考虑的因素以及相应的措施,并且给出了其主要性能指标的测试方法和结果。     

中间级接入掺铒光纤放大器及其自动增益校准

为了根据外界条件的变化自动进行增益调整,引入了中间级接入掺铒光纤放大器,它具有两级放大功能,增益在一定范围内可调,且能自动根据系统的变化调整自身的增益,使其满足不同条件的应用需求。采用自动增益校准的方法,对其原理进行了理论分析和实验验证,取得了中间级接入掺铒光纤放大器的增益校准及验证数据。结果表明,自动增益校准数据具有较高的准确性。这一结果对掺铒光纤放大器实现快速、准确的自动增益控制是有帮助的。     

Erbium-doped fiber amplifier with 54 dB gain and 3.1 dB noisefigures

It is shown that for practical pump powers (<100 mW) a combination of high gain (>33 dB) and low noise figure (3 dB) cannot simultaneously be achieved with a conventional codirectionally pumped EDFA. However, using a codirectionally pumped composite EDFA incorporating an isolator overcomes the problem, and an amplifier with 51 dB (54 dB) gain and 3.1 dB noise figure (NF) for only 45 mW (93 mW) of pump power is demonstrated     

宽带碲基掺铒光纤放大器上能级粒子数反转比

对宽带碲基掺铒光纤放大器(EDTFA)上能级粒子数反转比进行了理论研究,得到了碲基掺铒光纤放大器上能级粒子数反转比随着光纤激活长度、信号输入功率、泵浦功率和纤芯掺杂浓度的演变关系,分析了上能级粒子数反转比分布与EDTFA信号增益间的关系.研究表明,碲基掺铒光纤内的上能级粒子数反转比分布决定了EDTFA的信号增益.     

Erbium-doped fiber amplifier second-order distortion in analog links and electronic compensation

The authors study the second-order distortion when an erbium-doped fiber amplifier (EDFA) is used to amplify the analog optical AM cable TV (CATV) multiple carrier signal from a directly modulated distributed feedback (DFB) semiconductor laser. Experimentally, it was seen that this second order distortion depends critically on the gain of the EDFA fiber amplifier. The authors attribute this distortion to the interaction between the frequency chirping of the DFB laser and the variable gain with wavelength of the amplifier. The authors describe an electronic predistorter that compensates the nonlinearity produced by the DFB-laser-EDFA combination. As a result, the high power advantage of the EDFA can be fully realized in spite of the potential for second-order distortion in the system.<>     

Erbium-doped fiber amplifier pumped in the 950-1000 nm region

The pump wavelength dependence of the gain of an erbium-doped fiber amplifier pumped in the wavelength region 950-1000 nm is discussed. It is found that efficient gain at 1.557 μm, between 25 and 28 dB for 17 mW of launched pump power, can be obtained for any wavelength pump in the range 965-985 nm. The optimum length of erbium fiber needed is found to vary as a function of pump wavelength. The gain as a function of signal wavelength is also investigated at these pump wavelengths     

Erbium-doped composite glass waveguide amplifier

Optical amplification at 1.523 mu m wavelength is demonstrated in an erbium-doped glass waveguide. More than 10 dB amplification is achieved in a 4.7 mm long waveguide with about 30 mW guided pump power of 0.9734 mu m wavelength.<>     

掺铒光纤的研制

掺铒光纤主要用来制作掺铒光纤放大器(EDFA)和掺铒光纤宽带光源(EDFS),在制作工艺上有液相掺杂、气相掺杂和螯合物掺杂,鉴于国内现有的设备条件和技术,近年来在研制掺铒光纤的过程中,采用了传统的液相掺杂制作工艺,但对其进行了大胆的改进和优化,在掺铒光纤制作工艺上取得了重大进展,光纤参数明显提高,与国外的同类型光纤比较,差距大幅度缩小,主要参数已达到或接近国外同类型掺铒光纤水平,本底损耗达到3.74 dB/km,数值孔径为0.236,980 mm吸收损耗达到6.05 dB/m,在相当程度上已能够满足国内掺铒光纤放大器和掺铒光纤宽带光源研制单位对掺铒光纤的需要.     

Erbium-doped glasses for fiber amplifiers at 1500 nm

Material-dependent properties influencing the performance of fiber amplifiers are reviewed together with the available data for Er³⁺ . The major glass types potentially useful in this application are considered and compared to silica. The topics addressed include quenching processes and the solubility of rare-earth ions, transition strengths and bandwidths at the 1500-nm gain transition, and the characteristics at the 800-, 980-, and 1480-nm pump bands. Aluminum is shown to be an extremely useful codopant for silica, improving its ability to dissolve rare-earth ions and providing desirable spectroscopic properties for Er³⁺. For some of the attributes considered, other glasses have advantages over Al silica, but only with respect to gain bandwidth and pumping performance at 800 nm is significantly better than expected from other glass compositions     

Erbium-doped phosphosilicate glass waveguide amplifier fabricated by PECVD

An Er-doped waveguide amplifier fabricated by plasma enhanced chemical vapour deposition is described. A maximum net gain of 5 dB and a gain coefficient of 0.67 dB/cm are obtained in a 0.48 wt.% Er-doped waveguide pumped at 420 mW at a wavelength of 0.98 mu m. The 0 dB gain threshold is 23 mW.<>     

Erbium-doped fiber characterization by fluorescence dynamicsmeasurement

A technique for erbium-doped fiber characterization is presented. Its foundation lies in the study of the transversal and copropagating fluorescence time evolution when pumping is switched on and off. A model that describes these phenomena is developed, and experimental results, in good agreement with the model, are shown. The stimulated emission cross sections and an effective erbium-density distribution are determined from the measurements     

Multi-wavelength all-optical networks with wavelengths outside theerbium-doped fiber amplifier bandwidth

Erbium-doped fiber amplifiers have become the dominating technology for signal amplification in all-optical networks. One constraint of EDFA's is that they have a much narrower bandwidth (≈25 nm) compared to the low-loss region (≈200 mn) of optical fiber. Instead of using only wavelengths within the bandwidth of EDFA's (i.e. the inband channels) for communication, we propose to include wavelengths outside the EDFA bandwidth (i.e. the outband channels) as well in order to increase the number of wavelengths and/or channel spacings that can be accommodated. Using outband wavelengths for sending messages presents a new constraint, namely that only if the power loss for transmitting a message is small enough can this message be transmitted on the outband wavelength. We develop wavelength-routing algorithms on arbitrary network topologies and wavelength assignments in hierarchical networks for sending messages subject to this constraint. We also analyze the SNR for inband/outband WDM signals     

Erbium-doped fiber amplifiers: linear approximations

In this paper, we show that there is a simple linear model for an erbium-doped fiber amplifier. Specifically, we show that the amplifier gain, raised to a wavelength-dependent power, is strongly linear with respect to the amplifier-induced increase in signal power     

一种适用于HDTV的视放电路

详细介绍了高清晰度电视（ＨＤＴＶ）视频信号的特点,分析了视频放大电路的性能指标,结合ＨＤＴＶ信号特点设计了视放电路,并给出了以飞利浦公司生产的芯片（ＴＤＡ６１２０Ｑ）为核心的实用电路。     

Optimization of fiber amplifier SCM lightwave video systems usingdirect and external modulation

An analysis of the design factors involved in optimizing laser transmitters for SCM video distribution networks is presented. This includes optimization of the erbium-doped amplifier, linearized external modulation, and laser overmodulation to increase the optical loss budget. A full nonlinear distortion spectral analysis is employed to determine the dependence of the optimum optical modulation index on the allowable postamplifier loss. A general optimization procedure has been developed for the fiber amplifier and modulator to maximize the postamplifier loss for a specified CNR objective. Results are presented showing a comparison between the distribution capacity of direct and externally modulated SCM-EDFA systems for VSB-AM and FM-SCM transmission systems     

Multi-stream 3D video distribution over peer-to-peer networks

The recent advances in stereoscopic video capture, compression, and display have made 3-dimensional (3D) video a visually appealing and costly affordable technology. There have been a series of pioneer works on streaming 3D video over the Internet. Yet the remarkably increased data volume of 3D videos poses great challenges to the conventional client/server design, which has already suffered from supporting 2D videos.In this paper, we present an initial attempt toward efficient streaming of 3D videos over a peer-to-peer network. We show that the inherent multi-stream nature of 3D video makes playback synchronization more difficult, which is particularly acute with the existence of multiple senders in a peer-to-peer overlay. We address this by a novel 2-stream 2-stage buffer design, together with weighted data scheduling and light-weight synchronization. We further discuss a series of key practical issues toward implementing our peer-to-peer 3D video streaming system, including the weight modeling for data segments, the interactions with the RTP/RTCP protocol stack, and the inter-operability with monoscopic video as well as extension to multi-view video. We have evaluated the performance of our system under different end-system and network configurations with typical 3D video streams. The simulation results demonstrate the superiority of our system in terms of both scalability and streaming quality.     

面向移动内容分发网络环境的移动视频预取技术研究进展

随着移动互联网的发展和视频应用的普及,移动内容分发网络(MCDN)应运而生。预取技术是内容分发的关键技术之一,它通过预测用户未来的请求,提前将预测的内容预取至网络边缘,从而减少数据的获取时延、提升用户体验质量(QoE)。为深入阐述移动视频预取技术的发展现状,从用户移动行为感知、内容属性感知、网络资源感知等角度分析梳理了移动视频预取技术的最新研究成果,同时分析了各类预取方案的性能及其主要优缺点,最后指出未来可以进一步研究的方向。