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.     

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     

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     

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     

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     

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     

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     

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     

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.<>     

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.<>     

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.     

光纤放大器的泵浦问题

文章结合光纤放大器的工作原理和应用，对其泵浦光源的技术要求与泵浦光输入方式作了较为全面的阐述。由此可以看出，对于不同用途的光纤放大器，其泵浦光源本身和应用中的泵浦方式也是一个广阔的研究开发领域。     

Raman amplifier model in single-mode optical fiber

Equations to describe the process of Raman amplification in single-mode optical fiber and Stokes and anti-Stokes spontaneous emission generation with conservation of photon number are derived from first principles. The numerical simulation of Stokes and anti-Stokes spontaneous emission is in good agreement with experimental results. The importance of the sometimes-omitted anti-Stokes spontaneous emission terms in wavelength-division-multiplexed situations for optical signal-to-noise ratio is demonstrated by the simulation of light propagation through transmission fiber with and without Raman amplification.     

光纤参量放大器技术及其最新进展

介绍和论述了一种非常有实用前景的基于光纤非线性效应的光参量放大器(OPA)及其最新技术进展．最新发展揭示了它的很多技术特性优于传统的掺铒光纤放大器(EDFA)、半导体光放大器(SOA)和近年来很热门的光纤拉曼放大器(FRA),如对信号的调制形式、比特率的完全透明性、相位共轭、超宽的增益带宽、很低的噪声指数和具备优异的全光波长转换功能．     

基于F-P的光纤气体检测系统

简单介绍了利用F-P的可调谐性提出的一种新型的基于1550nm宽带光源的光纤气体检测系统的工作原理、实验装置软硬件设计以及利用该实验装置进行实验数据处理的思想--FFT一次谐波算法和计算光谱面积的算法.利用一次谐波的方法进行了实验,得出实验结果和结论.