An erbium-doped multimode optical fiber amplifier

The authors describe the first experimental study of an erbium-doped multimode fiber amplifier. The focus has been to characterize an intermediate core erbium-doped optical fiber, a fiber that is capable of propagating many guided modes at both the signal and pump wavelengths, and to determine the feasibility of using such an active fiber as a multimode fiber amplifier, by measuring its gain, noise, and pump power requirements. For a 2-m length of a 13-μm-core erbium-doped fiber, the authors measured gain as high as 16 dB at a signal wavelength of 1543 nm, with approximately 100 mW pump power (980 nm). For these same test conditions, the smallest excess noise factor β was 42     

基于电力线信道的自适应均衡设计

电力线除了传送电能外,还可以用作载波通信。但电力线信道中存在严重的码间干扰,信号衰减大,常用LMS算法对其进行均衡处理,这种算法简单易实现。但受步长因子限制,不能很好解决收敛速度与精度之间的矛盾。为适应电力线传送数据的要求,针对电力线信道传输特点,在现有均衡算法基础上,提出了一种基于抛物线函数的变步长算法,计算复杂度小,抗噪性强。仿真结果表明,该算法具有更好的收敛速度和精度,能有效提高电力线通信系统性能。     

Delay equalizer using twin T and one operational amplifier

An adjustable active delay equalizer network is presented, using a single operational amplifier and a twin-T feedback network.     

基于喇曼光纤的可变增益光放大器研究

通过分析WDM系统中全光增益控制EDFA(GC-EDFA)的优缺点,提出了一种新的可用于WDM城域网中的基于分布式喇曼光纤放大器的可变增益光放大器结构,并分析了通过监视前馈增益控制喇曼放大器的ASE信号来改善跨距损耗的扩展结构,使增益动态范围可从17dB变化到28dB以补偿跨损,当跨损变化从 5dB到-5dB时,能使输出光功率保持在0.15dB.     

S波段光纤放大器的研究

文章介绍了掺铥光纤放大器(TDFA)和增益位移掺铥光纤放大器(GS-TDFA)的基本工作原理.分析了不同的泵浦波长选择.随后,作者提出了一种使用半导体激光器泵浦两级高掺杂掺铥光纤的增益位移放大器方案.采用此方案的光纤放大器在30 nm工作带宽上光增益大于20 dB,饱和输出功率大于17 dBm,噪声指数为5.9～6.2 dB.     

Multichannel AM-VSB television signal transmission using anerbium-doped optical fiber power amplifier

The use of an erbium-doped optical fiber power amplifier in a multichannel amplitude-modulated vestigial-sideband CATV transmission system for potential subscriber loop applications is discussed. Using a color-center laser pump at 1.48 μm, a fiber-to-fiber gain of 11.5 dB (at 1.539 μm), which is 10 dB compressed from the small-signal gain, and a total system power margin of 15 dB were achieved. No intermodulation distortion was introduced by the fiber amplifier. The received video SNR of 40-46 dB was limited by the linearity of the distributed-feedback laser diode used     

41-nm 3-dB gain-band optical amplifier using an Er-doped core andSm-doped inner-cladding fiber without external filters

A new fiber structure optical fiber amplifier was reported where the core was doped with erbium (Er) and the inner-cladding was doped with samarium (Sm). Feasibility of gain control by evanescent wave interaction with an absorbing material in the inner-cladding was experimentally demonstrated. The optical amplifier using the proposed fiber resulted in the gain variation between gain peak and valley less than 2.5 dB without using external gain equalizing filters     

Dispersion-compensator incorporated optical fiber amplifier

An optical fiber amplifier incorporating a dispersion compensator such as a dispersion compensating fiber (DCF) is proposed and examined theoretically and experimentally. The new amplifier requires only a single pump laser. In the experiment a 0.98-μm laser diode was used and the pump power was 50 mW. By utilizing remnant pump power, the amplifier can halve the loss effect of the compensator and double the apparent figure of merit of the DCF (ps/nm/dB). The noise figure of the new amplifier is not affected by inserting the DCP. A low-noise figure of 5 dB was obtained over a wide input-power range of -40 to -10 dBm     

Digitally tunable channel dropping filter/equalizer based onwaveguide grating router and optical amplifier integration

We demonstrate a novel and powerful device that permits individual and simultaneous control of all the wavelength channels in a WDM system. The device is based on the monolithic integration of two identical waveguide grating routers with semiconductor optical amplifiers. By biasing appropriately the individual amplifier, each WDM channel can be amplified, detected or modulated. The device exhibits a channel bandwidth of 60 GHz, a channel spacing of 195 GHz and a crosstalk of -19 dB     

单模掺铒光纤激光器极限输出功率的数值研究

通过对掺铒光纤激光器极限输出功率的受限因素分析,在考虑非线性效应、热效应、光损伤等因素的情况下,结合掺铒光纤激光器的单模条件,计算得到单模掺铒光纤激光在1 570 nm 工作波段下的极限功率为6.34kW。同时计算了在少模条件下掺铒光纤激光器的极限输出功率为53.39 kW。还分析了单频情况下掺铒光纤激光器的极限输出功率,结果表明:在绝对单频的条件下,掺铒光纤激光器的极限输出功率为245W。并重点对实际中可行的提升输出极限功率的改善方法进行了分析,结果表明:降低纤芯数值孔径以及提升少模光束运转下的光束质量是提升单模条件下掺铒光纤激光器极限输出功率的重要手段。     

Prediction of gain peak wavelength for Er-doped fiber amplifiersand amplifier chains

We present a simple rule for predicting the gain peak wavelength (GPW) of an Er-doped fiber amplifier. For a given fiber type, the GPW is determined solely by the operating gain per unit length. Using this rule coupled with a simple Er-doped fiber amplifier model and measured modeling parameters, the GPW is predicted for a particular Er-doped fiber. The result is verified by direct measurement in a fiberloop. We demonstrate that the gain peak does not vary with pump power, pump wavelength or signal power as long as the gain per unit fiber length is fixed. Extension of this theory to include the wavelength dependences of other components in an amplifier chain is also discussed and demonstrated     

基于种子光特性优化的光纤放大器理论分析

种子光特性直接影响放大脉冲的特性,为获得高质量放大脉冲输出,文章对基于SESAM被动锁模光纤放大器中种子光的特性进行优化模拟。理论分析了锁模光纤激光器的单模光纤长度、增益光纤长度、滤波器带宽以及输出耦合比的变化对种子光特性的影响,以及种子光携带的啁啾对放大脉冲的影响。综合色散和非线性效应等对种子光的影响,得到各项参数的最优值,并进行两级放大模拟,最终获得脉冲宽度为1353 ps、光谱宽度为115nm、平均功率为61W的高质量放大脉冲。     

High-speed multiple-quantum-well optical power amplifier

A multiple-quantum-well optical amplifier is used at 8 Gb/s with high input power such that the average gain is compressed by 2.6 dB. Under these conditions, the output signal level is 35 mW and there is negligible intersymbol interference (ISI) penalty at the receiver. This is possible because of a rapid (7 ps) gain recovery process in the amplifier. A conventional semiconductor amplifier operating at a similar level of gain compression shows 2 dB ISI penalty     

First field demonstration of optical submarine cable system using LD-pumped Er-doped optical fibre amplifier

The authors report on the first field demonstration of an optical submarine cable system using an in-line Er-doped optical fibre amplifier pumped by a 1.47 mu m laser diode. The experiment was performed at an ocean depth of 3000 m. With a maximum optical repeater gain of 20 dB, 1.2 Gbit/s intensity-modulated optical signals were transmitted stably during and after installation and also during recovery of the system. Furthermore, the effectiveness of an automatic-gain-control (AGC) scheme proposed for optical amplifiers was confirmed in a practical environment.<>     

Raman fiber oscillator as optical amplifier

A Raman fiber oscillator used for optical amplification is demonstrated to have lower double Rayleigh scattering, transient spikes, cross-phase modulation, and higher saturation input threshold compared with a conventional discrete Raman amplifier at similar operating conditions. This could be a promising technology for deployment in practical systems.     

All-optical wavelength converter based on Er-doped laser cavity andintracavity LD amplifier

An optical wavelength converter is proposed based on a laser cavity that has a laser-diode amplifier as an optically driven gain modulator and an Er-doped, slow-response gain medium. The device converts ASK signal wavelengths over ~8.7 nm. Though the converted NRZ data signal is inverted, it is amplified by 18 dB with its extinction ratios improved to nearly unity. Although the data rate converted in the experiment is no more than 0.5 Mb/s, high-gain planar-waveguide technology may reduce the cavity length and increase the data rate     

OTDR in optical transmission systems using Er-doped fiber amplifiers containing optical circulators

Fault location in optical amplifier transmission systems is described. Optical time-domain reflectometry (OTDR) cannot be used for an optical transmission line containing traditional Er-doped fiber amplifiers (EDFAs) because they contain optical isolators. The authors propose an OTDR scheme that uses new EDFAs containing optical circulators and return transmission lines. The new EDFAs support both OTDR and digital signal transmission. A 280.9 km transmission line containing three of the proposed EDFAs was constructed and tested. Experimental results demonstrated the feasibility of OTDR fault location and 1.8-Gb/s digital signal transmission.<>     

基于多模光纤偏振烧孔效应的双波长掺铒光纤激光器

基于多模光纤(MMF)引入的偏振烧孔(PHB)效应,研制了一种环形双波长掺铒光纤(EDF)激光器.单模光纤(SMF)-MMF-SMF组成的结构使MMF不同偏振方向的反射模在波长上分开,利用PHB效应实现双波长的输出,输出波长间隔可通过改变MMF的长度改变.实验对比了1.6 m和3.0 m长的MMF输出波谱特性,结果表明...     

双泵浦两段高非线性光纤级联的光纤参量放大器

提出和设计了一种宽带宽、高增益和增益平坦的光纤参量放大器,它具有双泵浦和两段高非线性光纤级联的结构.选择光纤的四阶色散系数作为优化的指标之一,用普通的数组循环计算法,对双泵浦及两根高非线性光纤组成的系统进行模拟,获得了峰值增益62.46 dB,起伏小于5 dB,带宽高达424nm的光纤参量放大器.