A theoretical analysis of the effects of erbium ion pair on the dynamics of an optical gain stabilized fiber amplifier

In this paper, the effects of ion-pair formation on the gain dynamics of multi cavity optical automatic gain control erbium doped fiber amplifier is modelled. The inhomogeneous Cabezas simple model is used to write the rate and propagation equations for the active medium. The solution of the governing equations shows that in high concentration of the erbium ions, depending on the pumping rate, the relaxation oscillations are converted to nT-Periodic or even to chaotic behavior. Although the high concentration erbium ion in the optical amplifiers decreases the conversion efficiency and increases the threshold pump power, amplitude of the transient effects is reduced in the multi feedback-loop WDM amplifiers relative to the low concentration erbium ions multi feedback-loop optical amplifiers and ion-pairs, which act as a saturable absorber to compensate the gain tilt caused by the OAGC laser spectral hole burning. The theoretical results are in complete agreement with the previous published experimental results.     

半导体纳米晶体PbSe量子点光纤放大器

提出了一种新的光纤放大器——量子点光纤放大器(QDFA). 利用人工纳米晶体PbSe作为掺杂剂，通过解二能级系统速率方程和光传播方程，应用遗传算法和“逆方法"，计算得到了PbSe-QDFA的最佳掺杂浓度、抽运波长和光纤长度，并得到了增益、带宽和噪声系数. 与常规的掺铒光纤放大器相比较，PbSe-QDFA的带宽和噪声系数等关键指标均有明显提高，并可在长波长(约1630nm)区工作. 反演出极限QDFA所需的理想辐射和吸收截面. 理论模拟结果表明，在理想辐射和吸收截面下，QDFA的带宽极宽，噪声系数可接近量子 关键词： 量子点 光纤放大器 带宽 噪声     

Experimental and theoretical studies on a double-pass C-band bismuth-based erbium-doped fiber amplifier

Performance of a Bismuth-based Erbium-doped fiber amplifier is experimentally and theoretically investigated using 1480 nm pumping with double-pass scheme. In the theoretical analysis, the rate and power propagation equations are solved to examine the optimum length for the C-band operation as well as the gain and noise figure characteristics. The calculated small signal gain is 38 dB with gain variation of less than 3 dB. The measured gain is 4 dB lower due to spurious reflections which were ignored in the theoretical analysis. At input signal power of 0 dBm, a gain of 14.5 dB is obtained experimentally with gain variation of less than 1 dB within the wavelength region from 1530 to 1565 nm. The noise figure is less than 12 dB within this region.     

高峰值功率大模场全光纤脉冲放大器

报道了一种由纤芯直径分别为15 μm和25 μm的大模场光纤组成的全光纤脉冲放大器模块。当注入脉冲宽度为10 ns,重复频率为1 Hz,光谱宽度为0.3 nm,脉冲能量为80 nJ的激光脉冲时,经过两级放大输出的激光脉冲峰值功率为30 kW,单脉冲能量为300 μJ。此外,实验研究了该放大器模块输出的时间特性。研究发现：由于受激布里渊散射（SBS）效应,限制了单纵模光纤激光在光纤中的高能量放大,采用宽带激光脉冲可以有效地抑制SBS效应,提高光纤放大器的SBS阈值。     

Experimental and theoretical studies on ytterbium sensitized erbium-doped fiber amplifier

The performance of a high power erbium-ytterbium doped fiber amplifier (EYDFA) is investigated experimentally and theoretically. The EYDFA provides a flat gain with an output power higher than 23 dBm in the wavelength region from 1541 to 1565 nm using a multimode pumping at 927 nm. In the theoretical analysis, the rate and power propagation equations are solved to examine the effect of fiber length on the bandwidth of the gain spectra. In the C-band region, the small signal gain of the EYDFA varies from 30 to 34 dB with 10 m long erbium-ytterbium doped fiber (EYDF) while the 927 nm pump power is fixed at 3.5 W. It is shown that the calculated output power is in good agreement with the experimental results, verifying the feasibility of our theoretical model. However, the experimental result shows a relatively lower gain compared to the theoretical result due to the spurious reflection in the cavity and the insertion loss of the EYDF which were neglected in our theoretical model.     

高峰值功率大模场全光纤脉冲放大器

报道了一种由纤芯直径分别为15μm和25μm的大模场光纤组成的全光纤脉冲放大器模块.当注入脉冲宽度为10 ns,重复频率为1 Hz.光谱宽度为0.3 nm,脉冲能量为80 nJ的激光脉冲时,经过两级放大输出的激光脉冲峰值功率为30 kW,单脉冲能量为300μJ.此外,实验研究了该放大器模块输出的时间特性.研究发现:由于受激布里渊散射(SBS)效应,限制了单纵模光纤激光在光纤中的高能量放大,采用宽带激光脉冲可以有效地抑制SBS效应,提高光纤放大器的SBS阈值.     

基于混合光纤放大器的波分复用光纤传输系统研究

在研究了入纤功率、光器件的插入损耗以及非归零码中1码出现的概率对系统误码率影响的基础上,提出了一种基于混合光纤放大器的波分复用(WDM)光纤传输系统设计方案,并对该系统的噪声特性进行了详细地研究。提出了一种抑制前向噪声的有效方法,实现了20路WDM信号320km无误码传输。试验结果对基于混合光纤放大器的波分复用光纤传输系统的设计具有一定的指导意义。     

国产纺锤形增益光纤主振荡功率放大器实现5 kW输出

设计了纤芯直径小—大—小变化的“纺锤形”增益光纤,利用该光纤可均衡模式不稳定和受激拉曼散射抑制的矛盾,提升光纤激光器的输出功率。基于自研的纺锤形增益光纤搭建了主振荡功率放大器（MOPA）,实现了5 kW的功率输出,放大器光光效率为66.6%,拉曼散射抑制比大于45 dB,M²因子约2.0。通过优化光纤的设计,可以提升激光器的光束质量和效率。

     

Double-pass erbium-doped zirconia fiber amplifier for wide-band and flat-gain operations

The double-pass erbium-doped zirconia fiber amplifier (EDZFA) is proposed and demonstrated to provide a wide-band amplification as well as flat-gain operation in both the C- and L-band regions using only a single-gain medium. The proposed amplifier utilizes an erbium-doped zirconia fiber (EDZF) with erbium ion concentration of 2800 ppm as a gain medium. The medium is fabricated in a ternary glass host, zirconia-yttria-aluminum codoped silica fiber through solution doping technique along with modified chemical vapor deposition (MCVD). Compared to a single-pass operation, the double-pass EDZFA shows a better gain performance. At input signal power of 0 dBm and the optimum EDZF length of 2 m, a flat gain of around 16 dB is achieved by the proposed double-pass amplifier with gain variation of approximately 2.5 dB throughout the wavelength range from 1530 to 1590 nm. However, the noise figure of the double-pass amplifier is slightly higher than that of the single-pass due to inefficient population inversion at the input part of the amplifier.     

掺镱双包层光纤放大器分布泵浦方式下的优化算法

利用平均反转率迭代算法计算掺镱双包层光纤放大器分布泵浦方式下的稳态速率方程组,并采用遗传算法对分布泵浦功率的大小和每段光纤长度同时进行优化。评估函数中引入了每段光纤中最高温度的标准方差,以确保每段光纤中的最高工作温度是相同的。通过优化,7段泵浦的最高温度和标准方差分别为126.34 ℃和1.95 ℃ ,8段泵浦条件下的最高温度和标准方差分别为119.76 ℃和2.12 ℃。而未经优化的7段泵浦的最高温度和标准方差分别为147.12 ℃和21.37 ℃,8段泵浦条件下的最高温度和标准方差分别为139.95 ℃和20.83 ℃。计算结果表明：泵浦方式的优化降低了最高温度和标准方差,实现了光纤中温度分布的均匀性,并且通过增加泵浦段数可以进一步降低最高温度和平坦温度分布。     

掺镱双包层光纤放大器分布泵浦方式下的优化算法

 利用平均反转率迭代算法计算掺镱双包层光纤放大器分布泵浦方式下的稳态速率方程组,并采用遗传算法对分布泵浦功率的大小和每段光纤长度同时进行优化。评估函数中引入了每段光纤中最高温度的标准方差,以确保每段光纤中的最高工作温度是相同的。通过优化,7段泵浦的最高温度和标准方差分别为126.34 ℃和1.95 ℃ ,8段泵浦条件下的最高温度和标准方差分别为119.76 ℃和2.12 ℃。而未经优化的7段泵浦的最高温度和标准方差分别为147.12 ℃和21.37 ℃,8段泵浦条件下的最高温度和标准方差分别为139.95 ℃和20.83 ℃。计算结果表明：泵浦方式的优化降低了最高温度和标准方差,实现了光纤中温度分布的均匀性,并且通过增加泵浦段数可以进一步降低最高温度和平坦温度分布。     

Evolution of modes in double-clad Raman fiber amplifier

Stimulated Raman scattering in a double cladding optical fiber is studied with a continuous wave laser used as a pump source. Under various launch conditions, pump modes are differently excited. Considering the mode coupling effect among the pump modes, the evolution of the power in the Stokes modes is studied. The results show that the scattered waves （the Stokes waves） in the fiber core with 9%tm diameter and 0.14 NA could propagate predominantly in the fundamental mode of the fiber by carefully adjusting the pump light launching conditions.     

包层泵浦fs光纤放大器的实验研究

在实验上对双包层光纤放大器进行了研究。采用新型内包层为六边形的铒镱共掺双包层光纤作为放大介质,用带尾纤的半导体激光器进行泵浦,对fs光脉冲进行放大。当用2.5 W的入纤功率泵浦50 cm长的双包层铒镱光纤时,把平均功率为10.8 mW、重复频率20.84 MHz的激光放大到176 mW,增益为12.2 dB,相应的单脉冲能量为8.1 nJ,放大后脉冲宽度为480 fs,峰值功率为16 kW。     

A theoretical study of double-pass thulium-doped fiber amplifiers

An efficient fluoride-based thulium-doped fiber amplifier (TDFA) is theoretically demonstrated using a double-pass scheme. A reflector is incorporated in the double-pass TDFA to allow double propagation of the test signal in the gain medium and thus improve the gain of the TDFA. The small signal gain improvement of more than 15 dB is obtained in the 1465 nm region. A gain as high as 42 dB is obtained in this region with 300 mW of 1050 nm pump using 20 m of thulium-doped fiber. However, a noise figure penalty of approximately 1 dB is also obtained in this wavelength region. Differential equations are solved using the Runge-Kutta method in the theoretical analysis. The theoretical result is in agreement with the experimental result.     

A global design of an erbium-doped fiber and an erbium-doped fiber amplifier

A global design of an erbium-doped fiber and an open-loop erbium-doped fiber amplifier (EDFA) in a steady-state operation is discussed by applying genetic algorithms. Taking a signal gain and a bandwidth as objective functions, 7 parameters of the EDFA (erbium concentration, core radius, erbium-doped radius, refractive index difference, fiber length, pumping wavelength and signal power) are optimized by solving optical propagation equations, assuming a homogenous two-level active medium and a single-mode propagation. There is evidence to show that the 1480 nm pump utilized in usual EDFAs is not an optimal choice, which should be chosen around 1460 nm. The optimal core radius ranges 0.465–0.548 μm on pumping power 50–200 mW. Under different design objects and with different pumping powers, however, there are different optimal Er-doped concentrations, reflective index differences and fiber lengths. As a single fiber EDFA, 35 dB signal gain or 35 nm bandwidth is obtained with the 7 optimal parameters, 100 mW pumping power and 0.001 mW input signal power.     

Theory of pulse propagation and four-wave mixing in a quantum dot semiconductor optical amplifier

A theory, combining the relations of pulse traveling into quantum dot (QD) semiconductor optical amplifier (SOA) with the four-wave mixing (FWM) theory in these SOAs, is developed. Carrier density pulsation (CDP), carrier heating (CH), and spectral hole burning (SHB) contributions on FWM efficiency are discussed. Effect of QD ground state and wetting layer are included. An additional parameter appears in the gain integral relation of QD SOAs. An equation formulating pulses in the QD SOAs is introduced. We have found that FWM in QD SOAs is detuning and is pulse width dependent. For short pulses, CH is dominant at high detunings (10–100 GHz) while at higher detunings (>100 GHz) the SHB is the dominant one. Undesired paunch behavior is shown in QD SOAs then, CDP must be reduced.     

Remote all-optical nanosecond gain switching of an erbium-doped fiber amplifier

All-optical gain switching of an erbium-doped fiber amplifier located up to 50 km away from the signal and control lasers is demonstrated. The amplifier is deactivated by optical control pulses within the amplifier bandwidth that strongly saturate the gain at the signal Wavelength. Fall times are approximately equal to the control pulse duration of 21 ns. From 25 km, a maximum extinction ratio of 16 dB is demonstrated with the signal at 1527 nm and the control pulse at 1554 nm. The dynamic range for remote switching is limited by a stimulated Raman scattering of the control pulses.     

掺镱光纤放大器泵浦脉宽优化

为抑制低重复频率高能脉冲光纤主振荡功率放大(MOPA)系统的放大自发辐射(ASE)效应,达到脉冲泵浦的最佳放大效果,需要对泵浦脉宽进行优化。基于求解速率方程和功率传输方程,理论研究了脉冲泵浦下掺镱光纤放大器上能级粒子数密度、光纤内存储能量、正反向放大自发辐射的瞬态响应。在给定的泵浦功率、光纤长度、纤芯面积和掺杂数密度等参数下,数值计算得到的优化泵浦脉宽为793 s。此外,实验测定了ASE的建立时间; 通过调节泵浦脉宽,测定了脉冲泵浦下掺镱光纤放大器的放大效果,实验中得到的泵浦脉宽的优化值为800 s,证明了数值模拟的正确性。     

宽带碲基掺铒光纤放大器多信道增益竞争的仿真分析

对新型宽带碲基掺铒光纤放大器(EDTFA)多信道间的增益演变关系进行了理论仿真。仿真结果表明:EDTFA多信道间的增益存在着一个竞争过程,竞争的强弱取决于碲基掺铒光纤内的能级粒子数分布;当上能级粒子数处于反转分布态时,具有较大的发射截面与吸收截面差值的波长信道拥有相对较大的竞争优势,可获得相对较高的信号增益;当上能级粒子数处于未反转分布态时,具有较大的发射截面与吸收截面比值的波长信道拥有相对较大的增益竞争优势。     

包层泵浦fs光纤放大器的实验研究

 在实验上对双包层光纤放大器进行了研究。采用新型内包层为六边形的铒镱共掺双包层光纤作为放大介质,用带尾纤的半导体激光器进行泵浦,对fs光脉冲进行放大。当用2.5 W的入纤功率泵浦50 cm长的双包层铒镱光纤时,把平均功率为10.8 mW、重复频率20.84 MHz的激光放大到176 mW,增益为12.2 dB,相应的单脉冲能量为8.1 nJ,放大后脉冲宽度为480 fs,峰值功率为16 kW。