光纤放大器放大自发辐射特性与高温易损点位置

在高功率光纤放大器实验中,时常发现增益光纤抽运注入熔接点后10—50 cm处容易发生光纤烧毁现象.为了对该现象进行理论预测,基于光纤激光器速率方程模型和增益光纤的热传导模型,从种子功率、抽运功率和抽运吸收三个方面对掺镱双包层光纤放大器中的放大自发辐射(ASE)和温度特性进行研究.结果表明,在放大倍率较高、ASE较为严重等情况下,光纤放大器中的最高温度点一般不在抽运注入的熔接点处,而在距离熔接点10—50 cm处,与实验中发现光纤烧毁的位置基本符合.从光纤放大器的ASE抑制、最高温度点温度控制角度出发,对光纤放大器在种子功率、抽运功率、抽运吸收、放大倍率和抽运波长等方面的设计给出了指导性的建议.     

1410 nm波段分布式光纤拉曼增益放大器的研究

讨论了分布式光纤拉曼增益放大器的工作原理,采用1320nm固体激光器作为抽运源,获得了1410nm波段附近的光放大,在单模GI光纤长度为23km时,初步研究了拉曼放大器增益与光纤作用长度的关系,抽运脉冲峰值功率分别为50W、30W时,光纤的有效作用长度分别为15．5km和10.5km;研究了在不同的光纤有效作用长度时,拉曼放大器增益与抽运功率的关系;从光纤拉曼光谱图估算了光纤拉曼放大器的光谱宽度为50nm或250cm^-1。     

抽运方式对混合拉曼光纤放大器性能的影响

通过实验比较了前向抽运拉曼光纤放大器与掺铒光纤放大器组成的混合放大器、后向抽运拉曼光纤放大器与掺铒光纤放大器组成的混合放大器的性能。实验采用75km标准单模光纤作为增益介质。采用20信道(符合ITU-T建议的波分复用信号)，波长为1537．377～1560．605nm，作为混合放大器的测试信号。20信道总功率-2．86dBm，每一信道用2．5Gb／s、码长2^7-1的非归零码通过电吸收调制器(EA)进行外调制。实验结果表明，前向抽运方式混合放大器的性能优于后向抽运方式的混合放大器，其中噪声系数的改善值为2．28～6．55dB。采用前向抽运时，各信道的增益同后向抽运相比，增加值均大于5dB。但不论采取那种抽运方式，采用混合放大的形式，各信道的光信噪比均大于26．9dB。     

高功率光子晶体光纤放大器实验研究

利用掺Yb³⁺的光子晶体光纤作为光纤放大器的增益介质,采用反向抽运方式,分别从理论和实验方面研究了不同信号的增益特性,在信号光功率为6W,抽运光功率为160W时,获得了104W的输出功率.实验发现,当抽运功率大于一定值时,放大器输出会有一定的不稳定性,并影响输出功率的进一步提高. 关键词： 光子晶体光纤 光纤放大器 反向抽运 高功率     

同带抽运高效率光纤放大器

以光纤光栅为谐振腔搭建了波长为1020 nm的光纤激光器,并通过两级级联放大获得了590 mW的最大输出功率. 利用获得的波长为1020 nm的激光进行了波长为1064 nm种子光同带抽运放大,实验研究了不同增益光纤长度时放大器的输出功率和转换效率. 当增益光纤长度为8.5 m时,放大器最大输出功率为385 mW,斜率效率为81%. 进行了波长为976 nm的半导体激光器直接抽运波长为1064 nm种子光的实验. 在增益光纤长度最优时,其斜率效率为56.4%. 实验结果表明,同带抽运方式比传统抽运方式具有更高的转换效率. 研究结果可为波长为1020 nm的激光高功率放大和波长为1064 nm的光纤激光高功率同带抽运放大提供一定的参考. 关键词： 同带抽运 光纤放大器 斜率效率     

分布式光纤拉曼放大器在长距离光传输系统中的优化设计

同时考虑接收光信噪比(OSNR)及非线性失真影响，对分布式光纤拉曼放大器在长距离光传输系统中的最优抽运方式进行了研究.利用变分法原理获得了在不记双瑞利背散射(DRB)影响时的最优信号功率分布函数——均匀分布，但考虑双瑞利散射影响时则不存在解析的最优分布函数.在分别考虑长、短光纤跨距的情况下，比较了三种具有代表性的分布式光纤拉曼放大方式，即双向二阶拉曼抽运、双向一阶拉曼抽运和拉曼+掺铒光纤放大器混合放大方式的性能.指出通过优化一阶抽运波长以及一阶到二阶抽运功率比，对称结构的双向二阶抽运在绝大部分情况下可以在 关键词： 光纤拉曼放大器 双瑞利背散射 变分法 光纤非线性     

分布式反向抽运光纤拉曼放大器的功率转换效率分析

为了对反向抽运光纤拉曼放大器的功率转换效率进行研究,由耦合方程出发,采用龙格库塔算法和打靶法相结合的数值模拟方法,详细分析所有物理因素对反向抽运光纤拉曼放大器功率转换效率的影响。结果表明:功率转换效率先随着光纤长度增加而增加,当增加到最大值时保持数值不变;功率转换效率随着初始信号光功率、光纤拉曼增益系数、信号光损耗系数增加而增加,随着光纤有效面积、抽运光损耗系数、抽运光与信号光的频率比增加而减小;功率转换效率和初始抽运光功率呈抛物线曲线关系。所得结论对反向抽运光纤拉曼放大器功率转换效率的进一步研究以及光纤拉曼放大器的其他相关研究有重要参考意义。     

双向抽运光纤拉曼放大器的优化设计算法

基于双向抽运拉曼放大器的功率耦合方程 ,采用遗传算法和级链的全局收敛的Broyden方法 ,提出一种优化设计不同形式双向抽运宽带光纤拉曼放大器的自动配置算法。该算法的特点是计算速度快、收敛性好、适应面广。通过对单光纤的分布式、具有不同增益要求的分立式以及不同周期的色散管理结构的分布式双向抽运拉曼放大器的设计表明 :在 10THz的增益带宽内 ,放大器的增益平坦度均优于± 0 .6dB ,表明了该算法的可行性。此方法为采用双向抽运技术的拉曼放大器及其相应的全拉曼光纤传输系统的设计提供了一个公共平台     

大功率单频多芯光纤放大器中抑制受激布里渊散射的分析

针对多芯光纤完善了描述抽运光、信号光和Stokes信号的速率方程组.考虑了温差对受激布里渊散射的影响,利用有限元法求解温度分布方程组,分析了前向和后向抽运方式、对流系数、Stokes初始功率、光纤掺杂粒子密度和光纤长度对受激布里渊散射增益的影响.研究表明：后向抽运方式在抑制受激布里渊散射方面具有明显优势;减小对流系数有助于抑制受激布里渊散射;提高光纤掺杂密度能够加强抑制受激布里渊散射,同时也有助于提高光纤放大器的斜率效率.比较了在相同最佳光纤长度条件下,单芯和19芯光纤放大器的最高工作温度和受激布里渊散射 关键词： 光纤放大器 受激布里渊散射 大功率 有限元法     

高功率、低量子亏损同带抽运掺镱光纤放大器

开展了基于同带抽运的高功率、低量子亏损的掺镱光纤放大器实验研究. 搭建了一台输出功率为21 W的1018 nm短波 长掺镱光纤激光器, 并利用其对双包层掺镱光纤进行同带抽运, 获得18.6 W的1080 nm波段激光输出, 光-光转换效率高达90.86%. 关键词： 光纤放大器 同带抽运 双包层光纤 转换效率     

Intensity based erbium distribution for erbium doped fiber amplifiers

A method to calculate an optimum Erbium distribution to enhance the gain efficiency in EDFA is proposed. This method calculates Erbium distribution based on optical pump envelop, pump power and optical properties of Erbium ion. The intensity-based Erbium distribution is obtained for single-mode fiber and dispersion-shifted fiber types EDFA for pump power from 10 to 40 mW. All of the profiles have a Gaussian-like shape. For single-mode fiber type EDFA, high gain enhancement is obtained in a relatively short optimal length of fiber. Optimal length of EDFA, using intensity-based Erbium distribution, is increased by a factor of 1.5–3 with respect to the one using stepwise. This optimal length increasing factor is considerably smaller than that of the EDFA, using the one-fourth confinement Erbium profile.     

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.     

Bidirectional-pumped L-band erbium-doped fiber amplifier with pump distribution technique

A dual-stage erbium doped fiber amplifier (EDFA) having a flat gain wavelength response throughout L-band transmission window is presented. By applying pump power distribution technique, the pump power is distributed to two different stages with different length of EDF depending on the coupling ratio. By controlling these two parameters, gain of 19.1 dB with small gain variation of less than 0.5 dB and a noise figure of less than 10.5 dB are achieved in this architecture using bidirectional pumping. However, when another 3 dB power coupler is added to split the pump power equally at the second stage in bidirectional, a better noise figure of less than 7.5 dB was obtained. Comparison with a conventional single-stage optical amplifier was made in order to validate the performances of this dual-stage EDFA.     

Amplification enhancement of L-band erbium-doped fiber amplifiers by reflection scheme

A reflection L-band erbium-doped fiber amplifier (EDFA), which can effectively suppress and completely exploit the backward C-band amplified spontaneous emission (ASE) with a feedback reflection loop, is presented in this paper. The mechanism of the backward ASE secondary pumping effect is experimentally investigated in detail. Our experimental results have shown that, for a given input pump power, compared to the end-pumped EDFA, the gain and output power of the reflection EDFA can be improved considerably without paying much noise penalty. When the EDFA operates with flattened gain spectra, the gain is improved by about 7 dB with an extra noise penalty of about 1.2 dB, where the saturation output power is increased by 2.5–3.2 dB and which may also be made independent of the input signal power.     

Remotely Pumped Hybrid Amplifiers for Extended Bidirectional Passive Optical Networks

In this contribution, we optimize design parameters of hybrid optical amplifiers utilizing distributed Raman amplification in transmission fiber and gain of discrete, remotely pumped erbium-doped fiber amplifier (EDFA) for wideband, bidirectional operation in metropolitan area networks (MAN). The design is based on an application of a numerical model, which takes into account pump-to-pump and signal-to-signal interactions and generation of amplified spontaneous emission in the Raman amplifier and solves the standard rate-propagation equations in an erbium-doped fiber (EDF). We predict 12 dB gain across 72 nm of optical bandwidth with gain ripple better than 10%. The recently proposed serial topology of EDFA is considered; this enables the wideband, bidirectional operation of a hybrid amplifier with only two pump laser diodes emitting in the 1430 and 1480 nm bands.     

An experimental investigation of the gain spectrum of erbium-doped fiber amplifiers under various system configurations

The paper presents an experimental investigation of the gain spectrum of an erbium-doped fiber amplifier (EDFA) considering different system configurations, which include single-pass, double-pass, and double-pass with tunable band-pass filter (TBF). The role of TBF is to suppress the undesired amplified spontaneous emission (ASE). Both co- and counter-pumping schemes are considered with a 1480 nm laser diode as the pump and a suitable tunable laser source as the signal source. The results indicate that the signal achieves an average of 14 dB higher gain in the case of double-pass amplification with the implementation of a TBF. However, the pumping scheme hardly becomes of much importance in influencing the gain characteristics.     

LD泵浦掺铥(Tm3+)光纤激光器的数值分析

首先从掺铥光纤激光器的速率方程和光传输方程出发,建立数学模型,通过Matlab软件进行数值计算,分析了泵浦光和激光沿光纤的分布以及各能级离子数的变化.在不同掺杂浓度下,研究了小信号增益与入纤泵浦功率的关系以及泵浦光和激光功率与增益介质长度的关系.在不同泵浦功率下,研究了输出功率与输出耦合镜反射率的关系.进一步对不同泵浦吸收系数,研究了斜率效率和泵浦阈值与光纤长度的关系.分析结果表明存在最佳光纤长度和最佳耦合输出透过率,使得激光输出功率达到最佳值.     

双包层掺染料聚合物光纤放大器的增益性能分析

双包层聚合物光纤放大器可以减小染料的热漂白,使用速率方程的方法,给出了一个能够全面描述双包层掺染料聚合物光纤放大器增益性能的模型,模型既考虑了染料三重态能级对速率方程的影响,又考虑了双包层结构对泵浦光的影响,可以在稳态的情况下计算放大器的各种增益性能指标.     

General and effective dynamic gain spectrum control of broadband raman amplifiers with multi-wavelength pumping

An effective feedback algorithm is proposed to dynamically control the gain spectra of multi-wavelength pumped broadband Raman amplifiers. Based on Raman coupling power equations, a simple saturation factor is introduced to achieve the adjusting matrix. By using this method, efficient pump adjustment can be carried out to accomplish wide-range dynamic gain spectrum control (larger than 22 dB dynamic range) as well as automatic gain clamping even for 90 nm bandwidth, highly-saturated RAs. Moreover, this algorithm can be well applied to different fiber types as well as pumping schemes. Some useful guidelines are also demonstrated.     

The amplified model of erbium-doped fiber amplifier (EDFA) with cross-phase modulation (XPM)

Based on the rate equations and the power propagation equations, the amplified model is obtained which considers the cross-phase modulation (XPM)-induced intensity fluctuation between pump power and signal power in erbium-doped fiber amplifier (EDFA). Simulation results show: a higher nonlinear coefficient and a stronger pump power cause a stronger XPM in EDFA. Before the optimal length of EDF, the intensity caused by XPM increases with the increasing length, but after the optimal length, the XPM presents saturation. A bigger nonlinear coefficient γ corresponds to a smaller optimal length and gain, and makes gain saturation more easy. XPM effect will decrease EDFA’s amplified efficiency.