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     

Spectral dependence of gain and noise in erbium-doped fiberamplifiers

A two-level model of the erbium-doped fiber amplifier is used to analyze the dependence of the amplifier gain saturation, saturated output power, and excess noise factor on pump and signal wavelengths. Measured data are presented confirming that the dependence of the gain, output saturation power, and noise of erbium-doped fiber amplifiers on the signal and pump wavelength can be described by simple equations derived from the model     

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     

Gain peak wavelength measurements using a polarization scrambledfiber loop configuration

We present a quick and accurate method to measure the gain peak wavelength (GPW) of concatenated optical amplifiers in a long haul optical fiber communication system. This method utilizes a simple fiber-amplifier loop with polarization scrambling. We verify that the GPW of an amplifier is completely determined by the operating gain per unit erbium doped fiber length and changes linearly with compressed gain near 1.558 μm. The data presented, indicates how the GPW can be controlled for a broad range of operating gains by adjusting the erbium fiber length. The temperature and pump power dependence of GPW were found to be negligible for typical undersea system amplifier conditions. The gain bandwidth for concatenated amplifier systems appears to be a function of compression not operating gain, implying that wavelength division multiplexing systems requiring a flattened gain response should take this into consideration     

Performance of a distributed erbium-doped dispersion-shifted fiberamplifier

Continued improvements in the performance of a multi-kilometer, low-erbium-concentration fiber amplifier made by the modified chemical vapor deposition (MCVD) seed fiber method are discussed. Transparency for a -20-dBm signal at 1.55 μm and fiber length of 11.8 km was achieved with 20 mW of 1.48-μm copropagating pump power. The wavelength dependence of the gain for this signal level is reported, and the distribution in small signal gain along a 22-km length using an optical domain reflectometer (OTDR) was measured. Simulations are presented to show the effect of erbium concentration, input signal level, and pump power required for transparency of a 50-km span     

级联光纤参量放大器的增益特性分析

首先介绍了级联结构光纤参量放大器的工作原理,即通过两种光纤色散补偿来平坦信号输出增益。其次推导出小信号近似下单泵浦级联光纤参量放大器的信号输出增益表达式,并在此基础上利用Matlab软件对影响增益特性的各个参数进行数值分析。结果表明,级联光纤参量放大器的峰值增益与增益带宽,受到分段数、泵浦光功率、泵浦波长、色散补偿光纤(DCF)长度、高非线性光纤(HNLF)的零色散波长、HNLF长度、HNLF非线性系数和HNLF色散斜率的影响。     

Er3+-doped fiber amplifier pumped by 0.98 μm laserdiodes

The performance of an Er³⁺-doped fiber amplifier pumped by 0.98 μm InGaAs laser diodes (LDs) is reported. By using a fiber with low Er³⁺ content and optimizing the fiber length, a maximum signal gain of 37.8 dB at 30-mW pump power was realized at a signal wavelength of 1.536 μm. A maximum gain coefficient of 1.9 dB/mW at 14 mW pump power was achieved. It was found that the fiber amplifier pumped by the 0.98-μm LDs is twice as efficient as that pumped by 1.48-μm LDs, from the viewpoint of both required fiber length and the attained gain     

高功率光纤激光器反向光放大和损伤特性数值分析

利用速率方程模型对主振荡?功率放大器结构的1 μm波段掺镱（Yb）高功率光纤激光器中存在连续波反向信号光时的功率特性进行了理论分析,结果显示反向信号光功率会被高功率激光放大器所明显放大,10 kW级的光纤激光器中,100 W的反向信号经过放大器后功率会被放大至kW量级;与此同时,反向信号放大过程对反转粒子数的消耗会导致激光器的正向输出功率的严重下降。另外,反向信号放大也会导致放大器输出端的激光功率过强,加剧泵浦吸收和受激发射过程,增加该处的热负载、导致温度大幅上升100 ℃以上,对稳定性产生潜在影响。反向信号导致振荡器提供的正向种子光功率波动和下降时,正向信号不能充分饱和有源光纤中的增益,会进一步加强反向信号在主放大级中的放大作用,进而对系统造成更严重的影响。提高正向种子光功率、增强正向信号对激光增益的饱和作用,有助于抑制反向信号的放大过程,但需综合考虑种子源稳定性、热负载、热致模式不稳定和受激拉曼散射等因素合理选择种子光功率。     

Calculation of the noise figure of erbium-doped fiber amplifiersusing small signal attenuations and saturation powers

A theory allowing the noise figure of an erbium-doped fiber amplifier to be computed with a reduced set of fiber parameters is evaluated. The approach is accurate when the amplified spontaneous emission has no significant influence on the gain. Then four parameters, saturation power and absorption coefficient for pump and signal wavelength, are sufficient for 980-nm pumped fiber amplifier. This theory is used to investigate the noise characteristics of a 980-nm pumped booster amplifier within the whole gain spectrum     

掺镱双包层光纤放大器的放大特性

从掺镱(Yb)光纤放大器的功率传输方程出发,利用有限差分法对小模场面积(SMA)和大模场面积(LMA)掺镱双包层光纤放大器的放大特性进行了分析比较.采用模场直径(MFD)6.5μm和20μm的双包层掺镱光纤作为放大器增益介质进行窄线宽连续信号的放大,在915 nm激光抽运下模拟计算了大、小模场面积输出功率随输入信号功率、抽运光功率和光纤长度的变化特性,特别是对于大模场面积光纤放大器,最优光纤长度的选择至关重要;讨论了模场直径不同时的最优抽运功率和光纤长度的选择,得出4 m光纤放大时的临界抽运功率为4 W,理论与实验结果基本一致.为实际应用中根据信号光、抽运光、增益和模式等要求而选择光纤长度和类型等优化设计提供了理论依据.     

Suppression of stimulated Brillouin scattering in high-power single-frequency multicore fiber amplifiers

To describe the interplay between the first-order Stokes, pump, and signal in the multicore fiber amplifier, a set of differential equations is presented. The model takes into account the dependence of the stimulated Brillouin scattering (SBS) on the pump-induced temperature distribution along the fiber. The influence of pump schemes, pump powers, convective coefficient, density of the rare earth dopant (N) and fiber length on suppression of the SBS is studied. The backward pump scheme has advantage over forward pump scheme in suppression of SBS. For the SBS gain spectrum, reducing convective coefficient can decrease the maximum SBS gain and increase the frequency detuning corresponding to the maximum SBS gain. Increasing N can lead to higher slope efficiency and shorter optimal fiber length, which can further suppress SBS. The SBS gain (G) and maximum operating temperature are compared between the single core fiber amplifier and multicore fiber amplifier with the same optimal fiber length. Compared to the single core fiber amplifier, the multicore fiber amplifier has lower maximum operating temperatures, which provide more space for further increasing output power.     

Broad-band erbium-doped fiber amplifier with double-passconfiguration

We demonstrate a broad-band silica-based erbium-doped fiber amplifier (EDFA) with double-pass configuration. The signal gain and noise figure are obtained more than 24 dB and less than 6 dB, respectively, for 1526-1562 nm and 1569-1605 nm. The same signal gain can be achieved with 53% less pump power and 45% shorter erbium-doped fiber length, compared to a conventional parallel type EDFA. Furthermore, the noise figure and power conversion efficiency are improved for the wavelength range     

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     

光纤长度优化的高功率铒镱共掺光纤放大器

为了研究不同增益光纤长度下1555nm高功率光纤放大器的输出功率,采用两级混合结构的方法,用掺铒光纤放大器和双包层铒镱共掺光纤放大器分别作为1级预放大器和2级主放大器。掺铒光纤放大器对信号光进行预放大,并提高放大器的信噪比;双包层铒镱共掺光纤放大器为主放大器,其双包层结构可以把更多的多模抽运光耦合进系统。对铒镱共掺光纤的最佳长度做了理论分析和实验验证,在信号光功率为10mW、掺铒光纤放大器的抽运功率为318.58mW、双包层铒镱共掺光纤放大器的抽运功率为11.71W、增益光纤长度为14m时,输出功率取得了2.11W的实验数据。在分析输出信号光谱时发现,L波段附近有放大自发辐射谱出现,这是选择的增益光纤过长导致的。结果表明,在光功率和信号光功率一定时,光纤放大器有一个最佳的光纤长度。这一结果对研究光纤放大器的高功率输出是有帮助的。     

分布拉曼光纤放大的实验研究

采用符合ITU-T标准的G波段40信道波分复用(WDM)光源对分布式拉曼放大器(DRA)的特性进行了实验研究。对不同抽运方式及不同光纤长度的分布式拉曼放大器性能作了较为详细的报道。在抽运功率相同的条件下，选用50km单模光纤对比研究了不同抽运方式的拉曼放大器增益和噪声。通过对不同光纤长度的分布式拉曼放大器的实验研究发现，在较低抽运功率且输入信号功率较低的情况下，随着光纤长度增加，拉曼增益也增加，有效噪声系数减小。研究了分布式拉曼放大器对波分复用通信系统信噪比的改善，实验发现不同抽运功率下，拉曼放大器对系统信噪比的改善随抽运功率增加而增加，但是不成线性关系，而且最终会出现饱和。     

宽带平坦增益光纤喇曼放大器泵浦配置的快速搜索算法

本文提出了一种用于宽带平坦增益喇曼光纤放大器的泵浦配置的快速搜索算法,该算法只需要指定放大器采用的介质光纤参数、信号功率水平、放大器的目标增益和允许采用的泵浦数,就能够搜索到最小均方误差意义下泵浦的配置结果.算法利用最小均方差意义下的最佳逼近,把搜索波长的遗传算法和确定功率积分的具有线性约束条件的二次型凸规划问题结合起来,从而加快了搜索速度.     

多泵浦增益平坦光子晶体拉曼光纤放大器

针对密集波分复用光纤通信系统中拉曼光纤放大器增益及增益谱平坦问题,提出一种采用4个泵浦光的多泵浦方式在光子晶体光纤不同位置处注入两种不同波长泵浦光的组合方式来获得拉曼光纤放大器增益更大、增益谱更加平坦的方法。这种组合方式在拉曼光纤放大器中使得光信号实现了前段放大、后段补偿,从而在拉曼光纤放大器输出端获得高增益和较平坦增益谱。模拟的结果表明:平均增益可达:26.5 dB,增益平坦度为0.046 dB。     

掺铒光纤放大器的最佳光纤长度和增益特性

本文用三能级系统的速率方程建立了掺铒光纤放大器近似理论模型。在有激发态吸收时，各种泵浦波长下均获得了掺铒光纤的最佳长度。就增益随信号光及泵浦光光强的变化作了分析。通过对增益谱分析发现改变掺铒光纤长度可改变增益带宽，为掺铒光纤放大器在波分复用光纤通信系统中的应用提供了依据。     

Noise figure of erbium doped fiber amplifiers in the saturatedregime

We have made an experimental and theoretical study of the noise figure of an erbium doped fiber amplifier in the saturated regime. The saturated amplified spontaneous emission at the signal wavelength was measured using a very accurate pulsed source technique. We have quantified the noise figure dependence on compression, in excellent agreement with theory, to be less than 1.5 dB for a gain compression as high as 15 dB when the small signal gain was 26 dB, and the 1.48 μm pump power was 27 mW     

Tunable coherent optical transversal EDFA gain equalization

In this paper, we propose a fiber amplifier gain equalizer using a coherent optical transversal filter. The gain equalizer is tunable and has a bandwidth in the order of 30 nm. We also study the effects of different parameters such as input signal power pattern and the input pump power on the gain profile of the amplifier. The results show that, when the input signal power pattern changes, the amplifier does not maintain its gain profile. The gain profile has to be maintained in order to make the gain equalization effective. We show that, the pump input power can be adjusted so that the changes in the gain profile are compensated for. The gain profile varies quite slowly, hence compensation is feasible. As an example, we discuss the design of a gain equalizer for a system consisting of seven wavelength channels