Mode-dependent dynamic gain of all-fiber FM-EDFA under various pump manipulation

The dynamic gain of a few-mode erbium-doped fiber amplifier(FM-EDFA)is vital for the long-haul mode division multiplexing(MDM)transmission.Here,we investigate the mode-dependent dynamic gain of an FM-EDFA under various manipulations of the pump mode.First,we numerically calculate the gain variation with respect to the input signal power,where a modedependent saturation input power occurs under different pump modes.Even under the fixed intensity profile of the pump laser,the saturation input power of each spatial mode is different.Moreover,high-order mode pumping leads to a compression of the linear amplification region,even though it is beneficial for the mitigation of the differential modal gain(DMG)arising in all guided modes.Then,we develop an all-fiber 3-mode EDFA,where the fundamental mode of the pump laser can be efficiently converted to the LP_(11)mode using the all-fiber mode-selective coupler(MSC).In comparison with the traditional LP_(01)pumping scheme,the DMG at 1550 nm can be mitigated from 1.61 dB to 0.97 dB under the LP_(11)mode pumping,while both an average gain of 19.93 dB and a DMG of less than 1 dB can be achieved from 1530 nm to 1560 nm.However,the corresponding signal input saturation powers are reduced by 0.3 dB for the LP_(01)mode and 1.6 dB for the LP_(11)mode,respectively.Both theoretical and experimental results indicate that a trade-off occurs between the DMG mitigation and the extension of the linear amplification range when the intensity profile of pump laser is manipulated.

Gain performances of 980 nm-pumped erbium-doped fiber amplifiers

Through the introduction of the overlapping factors between the light (pump and signal) intensities and the erbium doping distributions inside the fiber core, analytical solutions of homogeneously broadened two-level systems for erbium-doped fiber amplifiers pumped in the 980 nm absorption band have been derived from EDFA rate equations and light propagation equations in steady-state case. By using these deduced expressions and numerical simulated methods, important features characterizing the amplifiers such as gain, pump threshold power, optimum fiber length have been analyzed and discussed.

Gain and Emission Spectrum Characteristics of 465 nm Laser Diode Pumped Tm3+-Doped Telluride Glass Fibers

Gain and emission spectrum characteristics of Tm3+-doped telluride glass fibers pumped with 465 nm lasers are analyzed. The rate and power propagation equation groups of the fibers are solved numerically and the effects of the fiber parameters including active ion concentration, length and pump power on the gain spectra and amplified spontaneous emission (ASE) spectra are analyzed. The results show that with a pump parameter of 465 nm/200mW, a doping concentration of 2.5×1025ion/m3and a fiber length of 16m, the gain and ASE spectra can cover from 1.100 to 1.900 μm, and the gain and ASE power peaks can reach 52 dB and 8mW, respectively. © 2017, Shanghai Jiaotong University and Springer-Verlag GmbH Germany.

Novelty Design in Gain Flattening Filter of ASE Source Based on Fat Ultra-Long Period Fiber Grating

A new type of gain flattening filter for amplified spontaneous emission （ASE） source based on erbium doped fiber （EDF） is proposed and demonstrated by fabricating and writing two series ultra-long period fiber grating （ULPFG） on single mode fiber （SMF-28）. The novelty method in this research is based on writing the two ULPFGs as fat gratings. The LPG is written by a simple and available arc-discharge method. The pump power based on single-pass backward pump configuration is around 100mW, and the average wavelength is near to 974nm. The gain flattening profile is obtained by 3.4 （±1.7）dB ripple in the wavelength range between 1524nm and 1565nm with 41-nm band width.

Differential mode-gain equalization via femtosecond laser micromachining-induced refractive index tailoring

The mode-division multiplexing technique combined with a few-mode erbium-doped fiber amplifier(FM-EDFA)demonstrates significant potential for solving the capacity limitation of standard single-mode fiber(SSMF)transmission systems.However,the differential mode gain(DMG)arising in the FM-EDFA fundamentally limits its transmission capacity and length.Herein,an innovative DMG equalization strategy using femtosecond laser micromachining to adjust the refractive index(RI)is presented.Variable mode-dependent attenuations can be achieved according to the DMG profile of the FM-EDFA,enabling DMG equalization.To validate the proposed strategy,DMG equalization of the commonly used FM-EDFA configuration was investigated.Simulation results revealed that by optimizing both the length and RI modulation depth of the femtosecond laser-tailoring area,the maximum DMG(DMGmax)among the 3 linear-polarized(LP)mode-group was mitigated from 10 dB to 1.52 dB,whereas the average DMG(DMGave)over the C-band was reduced from 8.95 dB to 0.78 dB.Finally,a 2-LP mode-group DMG equalizer was experimentally demonstrated,resulting in a reduction of the DMGmax from 2.09 dB to 0.46 dB,and a reduction of DMGave over the C band from 1.64 dB to 0.26 dB,with only a 1.8 dB insertion loss.Moreover,a maximum range of variable DMG equalization was achieved with 5.4 dB,satisfying the requirements of the most commonly used 2-LP mode-group amplification scenarios.

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.

Experimental optimization of an erbium-doped super-fluorescent fiber source for fiber optic gyroscopes

Double-pass forward and double-pass backward erbium-doped super-fluorescent fiber sources（EDSFSs） were combined in one configuration.A 980 nm laser diode pumped the same erbium-doped fiber from both directions using a coupler as a power splitter.The double-pass configuration was achieved by coating the fiber end face.Firstly,an optimal fiber length was found to obtain a high stability of output light wavelength with pump power, and then 1530/1550 nm wavelength division multiplexing was used for spectrum planarization,which expanded the bandwidth to more than 22 nm.The final step was a test of temperature stability.The results show that the rate of the central wavelength change kept to below 3.5 ppm/℃in the range of -40 to 60℃and 1-2 ppm/℃in the range of 20-30℃.Considering all the three factors of the fiber optic gyro applications,we selected 80 mA as the pump current,in which case the central wavelength temperature instability was calculated as 2.70 ppm/℃, 3 dB bandwidth 22.85 nm,spectral flatness 0.2 dB,output power 5.17 mW and power efficiency up to 9.92%.This experimental result has a significant reference value to the selection of devices and proper design of ED-SFSs for the application of high-precision fiber optic gyroscopes.

分布式宽带光纤喇曼放大器的研制

为了研究分布式光纤喇曼放大器研制过程关键技术,采用数值分析与实验相结合的方法,从理论上分析了受激喇曼散射耦合方程组,并对抽运光、信号光之间相互作用过程进行数值模拟,选择了满足增益要求的抽运源数目、波长和功率参量。实验上通过调节抽运功率配置,得到了C+L波段信号净开关增益大于10dB,平坦度小于1.6dB,偏振相关增益小于0.4dB,偏振模色散小于0.16ps。实验结果表明,本系统选择的抽运源参量完全满足喇曼增益设计要求,系统技术指标达到通信使用标准。

多泵浦喇曼放大器简化模型设计及泵浦优化

对多泵浦光纤喇曼放大器 (FRA)功率传输方程进行了合理简化 ,得到密集波分复用系统 (DWDM)信号合成喇曼增益的数学模型 ,分析了受激喇曼散射 (SRS)对信号喇曼增益的影响。并在该简化模型基础上介绍了一种对泵浦波长分布和输入功率进行优化计算的方法 ,实现了超宽带平坦的喇曼增益谱 ,为多泵浦FRA在DWDM系统中的应用提供了有价值的参考。

光纤喇曼增益系数的简捷测量

基于小信号开关增益原理 ,采用抽运光 探测波法 ,利用SLD(超辐射激光二极管 )作为宽带小信号探测光源 ,快速测量出了标准单模光纤 (G .6 5 2 )的频移为 0 .5～ 2 0THz内的喇曼增益系数 ,测量结果和文献中已有的值基本吻合 ,所测得的光纤喇曼增益系数可用于光纤喇曼放大器的理论和实验研究 。

分布式光纤喇曼放大器实验研究

为了对后向抽运分布式宽带光纤喇曼放大器的特性进行实验研究,采用多波长1426nm,1440nm,1460nm,1475nm和1495nm的半导体激光器作为抽运源,实现了C+L波段近80nm带宽的信号光放大,获得了比较好的平坦增益、偏振相关增益,系统平均开关增益为10.7dB,增益平坦度为1.5dB,最大噪声指数为-1.96dB,偏振相关增益小于0.4dB。结果表明,光纤喇曼放大器的抽运源波长、功率选择比较合理,系统所有技术指标均满足光纤通信使用要求。这一结果将对通信产业化发展有着重要的指导作用。

不同抽运方式下掺Yb^(3+)光纤放大器的增益和噪声特性

为了探讨不同抽运方式下掺Yb3+光纤放大器的增益和噪声特性,对910nm掺Yb3+光纤放大器进行数值模拟。结果表明,抽运方式对增益影响较小,但对噪声特性影响较大,光纤达最佳长度时,正向和双向抽运方式的掺Yb3+光纤放大器要优于反向抽运方式。这一结果对掺Yb3+光纤放大器的试验设计具有重要的作用。

光子晶体光纤放大器增益特性的实验研究

采用掺Yb3+双包层光子晶体光纤作为放大器的增益介质,在双端泵浦方式下,理论并实验研究了不同信号光时放大器的增益特性。在双端泵浦方式下,泵浦总功率为150.2 W、信号光功率为6 W时,获得了72 W的功率输出,斜率效率达到了60%。实验发现当泵浦总功率超过一定值时,由光纤端面反射形成的振荡腔引起放大器寄生振荡,并由于各种非线性效应出现了自脉动现象,影响了输出功率的进一步提高。

多抽运宽带喇曼放大器模拟算法的研究

基于龙格-库塔-芬尔格(Runge-Kutta-Fehlberg)方法,提出了一种求解多抽运宽带喇曼放大器耦合方程的自适应步长算法。该算法根据每步计算中局部截断误差和精度的要求,合理调整步长大小。仿真结果表明,与其它算法相比,自适应步长算法能有效地提高计算精度和效率,适合于光纤喇曼放大器的模拟计算。

正向抽运喇曼光纤放大器开关增益数值计算研究

采用数值计算的方法 ,对影响正向抽运喇曼光纤放大器 (RFA)开关增益的几个因素———喇曼增益系数、抽运光功率、光纤长度、光纤损耗、有效纤芯面积等参数与正向抽运喇曼光纤放大器开关增益的关系进行了分析研究 ,并把数值分析的结果和小信号的解析结果进行了比较 。

前、后向多抽运光纤喇曼放大器的增益特性分析

为了研究前向、后向多抽运光纤喇曼放大器的增益特性,在受激喇曼散射功率耦合方程组的基础上,采用龙格-库塔法结合打靶法分别计算了前、后向抽运功率、信号功率沿光纤的演化过程,并给出了抽运功率和信号功率的计算结果。结果表明,前向抽运系统中信号开始被放大,在最大处开始快速减小。低频抽运光的功率开始被放大的原因是由于抽运光之间的非线性相互作用引起的。后向抽运时信号开始被缓慢减小,然后在距离光纤末端处快速增加。这为以后喇曼光纤放大器的设计提供了重要的参考。

多波长泵浦拉曼光纤放大器增益最大化研究

应用遗传算法,对多波长泵浦的拉曼光纤放大器的增益最大化进行了研究.结果表明,当传输信号的波长、功率和信道数给定时,该算法能够给出增益接近最佳时的泵浦光的波长和泵浦能量的取值.对不同类型光纤的计算显示,单波长泵浦能获得较大增益的光纤,在多波长泵浦时不一定能获得较大增益.这为多波长泵浦的光纤拉曼放大器的设计提供了参考.

反向抽运光纤喇曼放大器增益特性分析

将打靶法和龙格库塔法两种数值计算方法相结合,对反向抽运光纤喇曼放大器中信号光和抽运光相互作用的耦合微分方程进行数值求解.在分别选取不同参量且取不同值的条件下,详细分析了光纤长度、初始信号光功率、初始抽运光功率、光纤有效面积、喇曼增益系数及光纤对信号光与抽运光的损耗等参量对增益的影响,最后提出了有效提高增益的方法.

新型增益平坦光纤喇曼放大器的研究

利用光子转换理论的前向受激喇曼散射(SRS)耦合方程,结合多波长泵浦和光纤级联两种方法,提出了一种新型的具有平坦增益的宽带光纤喇曼放大器(FRA)。采用数值解法对100信道的波分复用(WDM)系统进行了仿真,得到了宽带增益平坦的功率输出,为光纤喇曼放大器(FRA)增益平坦化提供了一种新的实现方法。

多泵浦光纤喇曼放大器的模拟分析(英文)

通过使用综合理论模型对不同配置条件下的多泵浦分布式光纤喇曼放大器的增益谱进行了数值模拟研究 ,该理论模型包含了瑞利散射、放大自发辐射和不同交互效应 ,包括泵浦与泵浦、泵浦与信号和信号与信号之间的交互与能量转移 模拟研究了泵浦源功率、泵浦源波长间隔及光纤损耗对喇曼增益谱的影响 ,结果表明设计多泵浦光纤喇曼放大器需要对泵浦源功率、泵浦源波长间隔光纤损耗谱进行综合考虑 ,需对泵浦源功率、泵浦源波长间隔进行合理配置 在本文的泵浦源波长设定条件下 ,考虑实际光纤的损耗谱特性 ,为了获得大的增益带宽和小的增益不平坦度 ,短波长泵浦源和最长波长的泵浦源需要更高的泵浦功率 。