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。     

基于改进粒子群算法的后向泵浦RFA设计北大核心CSCD

为了满足第六代移动通信(6G)系统对光通信网络的高速率及大容量的要求,进一步提高光传输网络中光纤放大器的带宽、响应速率及放大倍数等成为目前的研究重点。在使用碲酸盐光纤作为光纤增益介质的同时,提出一种改进粒子群优化算法,通过在迭代过程中动态的调整速度、位置及惯性权重值,获得更高收敛速度,增强全局搜索的能力。应用该算法对拉曼光纤放大器的各个泵浦光参数配置进行优化、分析及仿真验证,最终设计出平均开关增益为23.738 8 dB,增益平坦度为0.209 8 dB的后向泵浦拉曼光纤放大器。结果表明,改进的粒子群优化算法对拉曼放大器泵浦光的参数配置有很强的适应性,能够获得较低的增益平坦度,对未来拉曼光纤放大器的设计具有一定的参考意义。     

多波长光纤喇曼放大器及其泵浦优化

密集波分复用(DWDM)的发展对放大器的要求越来越高,多波长光纤喇曼放大器(MW-FRA)解决了放大带宽的问题,但由于多泵浦喇曼放大过程的复杂性,很难控制增益谱线的平坦度。文章分析了MW-FRA的泵浦和信号功率耦合方程,推导出增益表达式。比较了两种优化算法的优劣,并使用遗传算法对泵浦进行了优化。获得了较平坦的增益谱。     

双向泵浦受激拉曼散射增益谱平坦光纤放大器

研究现有的拉曼光纤放大器(Raman Fiber Amplifier,RFA)增益谱平坦化技术的不足,提出一种新型的拉曼光纤放大器的设计,即双向泵浦受激拉曼散射增益谱平坦光纤放大器。利用受激拉曼散射增益谱几乎在450cm-1波数处形成的对称结构,利用前向泵浦与信号光产生的频移对信号光进行放大作用,同时利用后向泵浦与信号光产生的频移对信号光进行补偿性的放大作用,从而实现双向泵浦受激拉曼散射增益谱平坦光纤放大器的设计。通过MATLAB的仿真验证,所设计的放大器增益平坦度高,信号光功率增益大,可实现双向泵浦受激拉曼散射光纤放大器的平坦化。     

多泵浦拉曼光纤放大器增益均衡的研究

基于受激拉曼散射原理,根据传输方程,用数值解法计算了单泵浦输入时的拉曼光纤放大器的增益;在此基础上,计算了多信道信号输入时,多泵浦拉曼光纤放大器的增益,并和文献的实验结果做了比较;用遗传算法优化泵浦参数以实现多泵浦拉曼光纤放大器的增益均衡。 1     

基于掺TiO2光纤的拉曼放大器特性研究

为探索能够应用于集总式拉曼放大的新型光纤材料,采用掺TiO₂光纤作为增益介质分别设计了一阶、二阶拉曼放大器。给出了高功率转换效率且增益平坦的泵浦参数配置方案,在总泵浦光功率不变的情况下对比了掺TiO₂光纤的一阶、二阶拉曼放大器与掺GeO₂光纤的二阶拉曼放大器的增益特性。仿真结果表明,在L波段60nm的谱宽范围内,32dBm的泵浦光前向注入长达6 km的掺TiO₂光纤对3 dBm的信号光进行二阶拉曼放大,其功率转换效率可达41.57%,增益平坦度仅为1.14 dB,对比掺GeO₂光纤的二阶拉曼放大器具有更平稳的输出增益。     

利用免疫算法优化设计的宽带大增益拉曼光纤放大器

为提高拉曼光纤放大器(RFA)的增益带宽和输出增益、改善增益平坦度,本文以掺铒碲基光纤作为放大介质,使用6个泵浦光设计了一款能够实现对C+L波段共100 nm带宽信号光平坦放大的拉曼光纤放大器.在设计过程中,针对拉曼光纤放大器模型中的非线性优化和组合优化问题,采用免疫算法配置泵浦光波长和功率的方法来解决,同时保证拉曼光...     

多泵浦拉曼放大器增益特性的仿真与分析

合理简化了多泵浦光纤拉曼放大器功率传输方程,利用多步平均功率法进行数值计算得到了密集波分复用系统信号的合成拉曼增益。借助该简化模型研究了多泵浦光源的个数、输入功率和波长分布对信号拉曼增益的影响,简单分析了实现超宽带平坦拉曼增益的多泵浦波配置原则,为多泵浦光纤拉曼放大器在密集波分复用系统中的应用提供了有价值的参考。     

反向多波长泵浦宽带FRA泵浦配置的一种优化方法

提出了一种基于粒子群算法(PSO)优化设计反向多波长泵浦光纤拉曼放大器(FRA)的方法.具体实施中应用PSO对6波长反向泵浦FRA的泵浦波长和泵浦功率共12个变量同时进行优化,然后依据泵浦光功率演变规律改进PSO算法,较好地克服了PSO优化精度低的缺点,最后得到了增益带宽100 nm,增益波动小于0.6 dB的优化结果,这为优化设计超宽带光纤拉曼放大器提供了一种可行的方法.     

Raman+EDFA混合宽带放大器增益谱优化的高效算法

采用遗传算法对Raman +EDFA混合放大器的增益谱进行了优化 ,根据二能级近似的EDFA模型及Raman功率耦合方程获得了简洁的适应度函数形式 ,可以在短时间内获得最优的放大器参数。计算表明 ,通过选择合适的拉曼抽运波长和抽运功率以及EDFA的平均反转度 ,仅用三个抽运源反向抽运的分布拉曼放大器加C波段EDFA就可以获得在 15 4 2～ 16 0 2nm共 6 0nm带宽上最大增益波动小于 1dB的平坦增益谱而无需额外的平坦滤波器。并对混合放大器的设计进行了讨论     

Extending transmission distance of high-density WDM systems usingpost transmitter fiber Raman amplifiers

The authors investigate the behavior of multichannel signals in a high-density wavelength division multiplexing (WDM) system with the consideration of stimulated Raman scattering. A parameter to evaluate the depth of Raman crosstalk is provided, and the transmission distance limitation imposed by Raman crosstalk is analyzed. To extend the system transmission distance, a post-transmitter fiber Raman amplifier is used. The allocation of signal channels on the pump gain profile is discussed. It is found that there exists an optimum pump power which results in a maximum amplifier gain. The example shows that the transmission distance limitation imposed by Raman crosstalk can be extended by 20 km for a 30-channel system with 0.25-dB/km fiber loss     

Efficient Pump Depolarizer Analysis for Distributed Raman Amplifier With Low Polarization Dependence of Gain

This paper discusses a method of reducing the polarization dependence of gain (PDG) of a distributed Raman amplifier. Reducing its PDG is important for a Raman amplifier because it is higher than that of an erbium-doped fiber amplifier and can degrade transmission performance. Raman PDG is determined primarily by two factors, namely 1) polarization-mode dispersion (PMD) of the transmission fiber and 2) degree of polarization (DOP) of the pump source. The authors propose a simple analytical model to show the required pump light DOP for a given transmission fiber's PMD and the allowable PDG. For instance, a low pump DOP of 5% produces a low PDG of 0.2 dB under typical fiber PMD conditions, in which the analytical model agrees well with experiment. Subsequently, to achieve the required DOP, the pump source configuration is investigated in detail. The authors used one length of polarization-maintaining fiber (PMF) as an efficient pump depolarizer and evaluated its performance for various pump light spectra. It has been shown that the DOP following the depolarizer is determined simply by Fourier transformation of the pump light spectrum. The analysis in this paper has led to the important result that a Fabry-Perot laser diode pump with a short piece of PMF is effective in achieving a low pump DOP due to its multimode spectrum when the length of the PMF is properly adjusted for the longitudinal-mode spacing frequency. It has been verified that a Raman amplifier's PDG can be reduced by the proposed efficient depolarizer sufficiently for a PDG-reduced Raman amplifier repeater to be applicable to long-haul transmission systems     

Amplified spontaneous emission in pulse-pumped Raman amplifiers

We discuss amplified spontaneous emission (ASE) generated in Raman amplifiers that are counter-pumped with trains of pulses. Our experimental and theoretical results show that if the peak power of the pump pulses is too high, the ASE output from the amplifier can be significantly higher than that from a continuous-wave pumped amplifier providing the same gain. This effect places a lower limit on the duty cycle of pump pulses one can use for a given level of Raman gain. Furthermore, we report an additional ASE enhancement if there is insufficient walkoff between the pump pulses and copropagating ASE to average the effects of higher frequency pump intensity noise. As a result, less pump intensity noise can be tolerated when pulse-pumping a fiber having a zero-dispersion wavelength located midway between the pump and signal wavelengths.     

Raman pulse compression of excimer lasers for application to laser fusion

Application of efficient ultraviolet excimer lasers such as the 248 nm KrF laser to laser fusion requires that long laser pulses be efficiently converted to short pulses at high intensity. The backward Raman amplifier is shown to be a promising candidate for this application. Gain, saturation, and limits to amplifier performance are described. It is shown that pump beams of poor spatial quality may be converted to output beams of high spatial quality. Several common gaseous vibrational Raman scatterers are discussed, and it is shown that a simple KrF-pumped backward Raman amplifier using methane at atmospheric pressure will have a saturation fluence near 1 J/cm²and can produce an output five times as intense as the pump in a ten times shorter pulse with an efficiency of about 50 percent. Design tradeoffs and possible techniques for further improving the performance of such amplifiers are discussed.     

光纤Raman放大器

本文介绍了Raman放大的机理、泵浦源及泵浦方式,分析了FRA的设计原则、增益均衡的各种方法、噪声及Raman串扰等问题,提出了可行的方案。     

DCF光纤拉曼放大器的实验研究

DCF(dispersion compensating fibre)光纤具有较高的拉曼增益系数,利用这一点可以用较短长度的DCF光纤制成分立式的光纤拉曼放大器,作为传输线路上的损耗补偿.本文在测量并计算了DCF光纤的拉曼增益系数的基础上,对分立式的DCF放大器的开关增益和噪声指数进行了测量和分析,并将分立式FRA和分布式FRA在开关增益和噪声指数方面做了比较。介绍了用不同的测量方法所造成的实验结果的差异.实验结果表明,放大介质为5 km的DCF光纤所构成的放大器,在抽运功率为800 mW的条件下,最大增益可达14.77dB,3 dB带宽为35 nm,满足作为损耗补偿的要求.     

Intensity averaging and four-wave mixing in Raman amplifiers

Intensity averaging of pump beams in a Raman amplifier can be treated using a four-wave mixing model. The model shows explicitly the consequences of finite pump beam correlation length in four-wave mixing processes. Phase conjugate effects in a Raman amplitier are observed and described. Measurements of four-wave mixing effects in a KrF laser-pumped methane Raman amplifier agree with the model.     

Extinction ratio degradation in Raman amplified optical communication system

The extinction ratio of a Raman amplified optical fibre system is investigated. The results show that serious extinction ratio degradation occurs at high pump level. Because the Raman gain increases with pump power, there exists a trade-off between the extinction ratio and the achievable amplifier gain. A design rule to estimate the suitable pump power is presented.<>     

A novel method for Raman amplifier propagation equations

A novel numerical method for the standard propagation equations of Raman amplifiers with multiple pumps is presented and derived based on the four-step Adams-Bashforth method. Our proposed multistep method can increase the accuracy and stability in designing Raman amplifiers compared with the one-step method. Output signal, pump, and backscattering pump powers have been numerically simulated and compared by utilizing our multistep method and one-step method. The results show that our method can reduce the computing time over three orders of magnitude with excellent accuracy by comparison with the direct integration method for the Raman amplifier propagation equations.