频率失谐对掺镱光纤放大器中光脉冲传输特性的影响

为了研究光脉冲在掺镱光纤放大器中的放大传输特性,建立了光脉冲在分布式光纤放大器中的传输方程,采用分步傅里叶变换法数值模拟了光脉冲的传输状态,并着重讨论了频率失谐对光脉冲特性的影响。结果表明：对于掺镱光纤放大器,在介质的色散长度远远小于非线性长度时,随着在放大器中的传输,光脉冲在放大的同时被展宽,脉冲中心出现峰值,其频谱加宽;当出现频率失谐时,光脉冲放大能力减弱,脉冲失去对称性,并且窄化。若光脉冲中心频率沿不同的方向偏离介质增益峰值频率,脉冲变形规律不同。因此在设计放大系统时应该考虑光纤放大器的色散以及频率失谐对其传输特性的影响。     

The Quantum Theory of Optical Pulses Amplification

The propagation of optical signals in optical fiber amplifier is treated with fully quantum mechanics method in this paper. The micro-Hamiltonian of the system with nonlinear effect is derived by combining spatial mode and temporal mode, and propagation equation of optical pulses in a optical fiber amplifier is derived with dispersion relation. The characteristic parameters such as gain, output power and noise figure of the amplifier are analyzed and their quantum mechanics formulas are obtained.     

超短光脉冲通过分布式光纤放大器的传输特性

为了探讨超短光脉冲在分布式光纤放大器中的传输放大特性及影响因素,建立了光脉冲在光纤放大器中的基本传输方程,以掺镱光纤放大器为例,采用分步傅里叶变换法对放大器中光脉冲的演变进行了模拟,讨论了初始啁啾和增益色散的影响。结果表明,当光脉冲在分布式光纤放大器中传输时,光纤的色散、非线性效应均会影响脉冲的形状和频谱,光脉冲初始啁啾也会对脉冲的传输状态产生影响;对于宽频谱光脉冲,增益色散相当于一种损耗机制,应该考虑其影响。相关结果对光纤放大器的系统设计和优化具有一定的参考价值。     

光孤子在分布式光纤放大器中传输特性的研究

光纤放大器用于补偿光信号在光纤中的传输损耗,是全光通信网中的核心器件。建立了光孤子在分布式光纤放大器中传输的物理模型,采用分步傅里叶变换法数值模拟了光孤子的传输放大特性,讨论了增益色散对光孤子形状和频谱的影响。结果表明：在放大器的反常色散区,随着光孤子的放大,会不断地产生啁啾孤子,孤子频谱会加宽并且产生振荡结构。放大介质的增益色散将会使光孤子幅度下降,宽度展宽,频谱窄化。因此,光纤放大器的色散、非线性效应和增益色散均会对光孤子的传输特性产生影响。     

1064 nm抽运掺铥光纤放大器增益特性的理论研究

从掺铥光纤放大器的速率方程组和光传输方程出发 ,引入光场与掺杂分布的重叠因子 ,利用数值法分别模拟计算了光纤掺杂浓度、长度和抽运功率等参数对放大器增益的影响 ,并计算了一定掺杂浓度和抽运功率下的最佳光纤长度及其对应的增益 ,分析了该类放大器增益随输入信号功率的变化关系 ,并计算了其功率转换效率。     

Effect of Soliton Propagation in Fiber Amplifiers

The propagation of optical solitons in fiber amplifiers is discussed by considering a model that includes linear high order dispersion, two-photon absorption, nonlinear high-order dispersion, self-induced Ramam and five-order nonlinear effects.Based on traveling wave method, the solutions of the nonlinear Schrodinger equations, and the influence on soliton propagation as well as high-order effect in the fiber amplifier are discussed in detail.It is found that because of existing five-order nonlinear effect ,the solution is not of secant hyperbola type, but shows high gain state of the fiber amplifier which is very favourable to the propagation of solitons.     

High-Power 1.06-$mu{hbox {m}}$ Near-Diffraction-Limited Planar Tapered Amplifier Injected With Seed Light Through a Fiber Biconical Microlens

We designed a 1.06-mum single-quantum-well (SQW) InGaAs/AlGaAs planar tapered amplifier that was injected with seed light of a fiber Bragg grating stabilized laser diode through a fiber biconical microlens. To increase the amplifier output, the microlens with approximately 3- and 11-mum radii on vertical and horizontal axes, respectively, provides high coupling efficiency between the laser diode and the amplifier. The microlens also controls propagation in the tapered gain area to suppress the filament formation. In addition, the small radii of the microlens reduce near-end reflection at the amplifier input to prevent parasitic laser oscillation of the amplifier. We demonstrated near-diffraction-limited output of 5.5 W with the beam quality factor M² of 1.5 by using a 3-mm-long amplifier having an optical confinement factor of 1.2%.     

Adiabatic soliton compression of gain-switched DFB-LD pulse bydistributed fiber Raman amplification

Using a dispersion-shifted single-mode fiber pumped by laser diodes as a distributed fiber Raman amplifier, the authors adiabatically compressed transform-limited (TL) pulses generated by a gain-switched distributed-feedback laser diode followed by linear compression and a spectral window. The initial TL pulses were successfully compressed asymptotically to almost pure solitons as short as 3.6 ps at the 2.4 dB total gain of a distributed fiber Raman amplifier, even without using solitons as the initial pulses. The experimental results are well supported by numerical calculations made with the beam propagation method     

Nd-doped double-clad fiber amplifier at 1.06 μm

We propose and demonstrate a double-clad neodymium (Nd)-doped fiber amplifier (IVDFA) at 1.06 μm for a compact configuration of a high-power optical amplifier. The proposed 125 μm first cladding diameter in the double-clad fiber, provides the single-mode propagation of the signal lightwave into its doped core without misguiding the signal lightwave into the outer core (first cladding), by simply splicing with a standard single-mode fiber. Furthermore a fiber grating in a single-mode core of the double-clad fiber allows the double-pass configuration for the signal lightwave at 1.06 μm and also allows the pump lightwave coupling at 0.81 μm into the first cladding without employing a bulk dichroic mirror. We demonstrate the signal output power of 110 mW for a 550-mW pump input from a multimode fiber coupled pump source. Theoretical results predict an efficient high-power operation of the amplifier by improving the signal scattering loss in the double-clad fiber     

Improved transmission of chirped signals from semiconductor opticaldevices by pulse reshaping using a fiber Bragg grating filter

Spectral filtering of chirped signals with an edge of a fiber grating filter improves propagation in nondispersion-shifted fiber. The improvement is due to a temporal shift of the frequency modulation with respect to the amplitude modulation. By filtering the chirped output of a semiconductor optical amplifier (SOA) wavelength converter with a fiber grating edge we obtain error-free transmission of converted data through 100 km of nondispersion-shifted fiber at 5 Gb/s     

超宽带Er,Tm共掺石英光纤放大器稳态研究

分析了波长为980nm激光抽运下的Er3+,Tm3+共掺石英光纤放大器的工作原理,并根据此工作原理,建立了Er3+与Tm3+之间能量转移过程的数学模型。基于速率方程和功率传输方程,数值模拟了此种光纤放大器稳态工作特性,给出了不同光纤长度、不同输入抽运功率以及不同掺Tm3+浓度下多路光信号放大时输出信号功率谱的变化规律。仿真结果表明,当输入抽运功率为400mW时,Er,Tm共掺石英光纤放大器的3dB带宽可达90nm(比传统掺Er3+光纤放大器的增益带宽大两倍以上),平均增益可达10dB,可用于未来密集复用系统(DWDM)中的宽带放大器件。     

光纤放大器中有限增益带宽对自相似脉冲放大演化的数值研究

通过求解包含超高斯增益系数滤波项的分布增益非线性薛定谔方程,模拟研究了短脉冲在有限增益带宽指数增益光纤放大器中的自相似演化行为及其差异。结果表明脉冲在不同指数增益分布放大器中传输时都会受到增益带宽的限制。相同输入脉冲在相同长度、相同总增益的指数上升、下降和双向分布放大器中放大时,在双向分布放大器中输出能量最高,输出脉冲线性啁啾特性最好,指数下降放大器输出能量最低,输出脉冲线性啁啾特性最差,指数上升放大器居两者之间。另外,总增益相同时,无论是指数上升、下降和双向分布放大器,初始增益系数较小,输出脉冲能量较高,脉冲线性啁啾特性较好。     

Comparison of optical back propagation schemes for fiber-optic communications

Optical back propagation techniques that utilize two highly nonlinear fibers to compensate for transmission fiber nonlinear effects are analyzed. When the step-size is equal to the amplifier spacing, inline compensation of fiber nonlinearity without inline dispersion compensation provides the best performance.     

Modified split-step Fourier method for the numerical simulation ofsoliton amplification in erbium-doped fibers with forward-propagatingnoise

Using a modified version of the split-step Fourier method, we analyze the effect of noise on soliton propagation inside erbium-doped fiber amplifiers. In fact, noise from forward-propagating amplified spontaneous emission, associated with a Markov immigration process, is included in the analysis of soliton amplification. Moreover, this algorithm accounts for the real spectral gain profile of the fiber amplifier. The frequency jitter, induced during soliton amplification, is compared with the Gordon-Haus effect where optical amplifiers are considered as noisy point-like devices     

Double Clad Er-doped Fiber Amplifier

Presented is a theoretical study of double-clad Er-doped fiber power amplifier（EDFA）. Two kinds of double clad fibers（DCF） with rectangular and ＂flower＂ inner clad shapes are studied, and these fibers have different coupling constants and propagation losses. We calculate the effective pump power absorption ratio along the fiber with different coupling constants from the first cladding to the doped core and with different propagation losses for the power in the inner cladding. Then the gains of the double clad Er-doped fiber amplifiers versus fiber lengths are calculated using the EDFA model based on propagation and rate equations of a homogeneous, two-level medium.     

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。     

10Gbit／s级联光纤放大器通信系统的传输距离

本文数值模拟了强度调制光信号在级联光纤放大器常规ＳＭＦ通信系统中的传输,在模拟中主要考虑了自相位调制、群带色散和ＡＳＥ噪声。我们使用负色散补偿光纤去补偿群速色散和自相位调制。结果表明如果色散得到很好的补偿,当放大器的间距减少到５０ｋＭ时,无误码２０５０ｋｍ传输是可能的。     

Impact of dispersion fluctuations on the noise properties of fiber optic parametric amplifiers

The effects of zero-dispersion wavelength (ZDWL) fluctuations on the noise characteristics of fiber optical parametric amplifiers (FOPAs) are investigated. The numerical derivation of the noise figure (NF) in terms of the amplifier operating conditions and the magnitude of ZDWL fluctuations is achieved by utilizing a simulation method based on the three-coupled propagation equations. The numerical analysis shows that the average NF of FOPAs is increased compared with the case of uniform dispersion, especially at high-gain operation. Apart from the NF, the gain-to-NF ratio is also evaluated to assess the amplifier performance for a variety of amplifier operating conditions and dispersion profiles.     

Surviving-Channel-Power Transients in Second-Order Pumped Lumped Raman Fiber Amplifier: Experimentation and Modeling

In this paper, the effect of addition and/or dropping of wavelength-division-multiplexed channels in an all- optical gain-clamped (AOGC) second-order (SO) pumped lumped Raman fiber amplifier (LRFA) has been investigated experimentally and analyzed by numerical simulation. Channel addition/ removal was simulated by transmitting ten signals through a counter-directionally pumped LRFA consisting of a 16-km-long dispersion-compensating fiber. The light from eight lasers was square-wave modulated at 500 Hz; power transients of the surviving channels caused by cross-gain modulation of the LRFA were monitored at the output of the amplifier. All-optical feedback loop was implemented in the form of a ring laser. Gain-clamping properties of the SO-pumped LRFA are compared with those of the first-order pumped LRFA having the same ON/OFF Raman gain. Theoretical analysis of the AOGC LRFA was based on numerical solution of coupled propagation equations for the backward propagating pump, signals, and both forward and backward propagating spectral components of amplified spontaneous emission powers.     

铒铥共掺碲基质宽带光纤放大器研究

文章作者分析了铒铥共掺碲基质光纤放大器在980 nm泵浦下Er~(3+)-Tm~(3+)离子之间的能量转移过程,建立了速率方程和功率传输方程,并通过仿真得出了其放大增益随光纤长度和泵浦功率的变化规律.仿真结果表明:通过优化光纤长度和泵浦功率,该放大器可以在1 440～1 540 nm波段得到高达50 dB的平坦增益.