Requirements for Efficient Raman Amplification and Dispersion Compensation Using Microstructured Optical Fibers

Abstract

The design and performance of microstructured optical fibers (MOFs) for simultaneous dispersion compensation and Raman amplification is numerically investigated. We studied a lumped Raman amplifier designed to compensate the signal loss and dispersion introduced by a 100-km, 16-channel C-band WDM link. The impairments induced by the nonlinearities caused by the small mode area of the designed MOF are investigated and the analysis is extended to include non-ideal factors such as excess background losses, splice loss, and the geometry variations during the fabrication process. The results are discussed and compared to those obtained for conventional dispersion compensating fibers (DCFs).     

色散缓变光纤中飞秒孤子压缩与稳定传输

运用数值方法研究了色散缓变光纤中飞秒基本孤子的传输特性，发现基本孤子脉冲不仅能被压缩，而且压缩光脉冲能保持脉宽不变转输即稳定传。光脉冲压缩过程中，发现三阶色散效应有较大的影响。适当地选取色散缓变光纤结构参数可能获得高质量的超短压缩光脉冲。对压缩光脉冲稳定伟机理探索表明，光纤二阶色散纵向变化率，三阶色散与喇曼自散射效应共同作用导致压缩光脉冲稳定传输。     

光子带隙光纤的可调谐泄漏损耗特性的研究

通过向折射率引导型光子晶体光纤的空气孔中填充可调的高折射率的材料可以获得带隙可调的光子带隙光纤.本文采用矢量平面波展开法与矢量有限元法对可调光子带隙光纤的泄漏损耗特性进行了理论研究.研究表明，这种可调光子带隙光纤的光子带隙效应使其泄漏损耗与填充材料的折射率有很强的依赖关系，同时给出了光子带隙光纤的泄漏损耗和群速度色散与归一化波长的关系.     

Thermal characteristics of erbium doped fiber amplifier pumped by Ti: Al_2O_3 tunable laser at 800nm-band

The temperature gain dependence of an Er~(3 )-doped fiber amplifier, which is pumped by a Ti : Al_2O_3 tunable laser at 800nm band, is investigated. At liquid-nitrogen temperature of 77K, gains higher than those of 300K are obtained, but the optimum pumping wavelength has a blue shift.     

色散缓变光纤中飞秒光脉冲的调制不稳定性研究

研究了色散缓变光纤中飞秒光脉冲的调制不稳定性 ,发现当色散缓变光纤的色散参量满足一定关系式时 ,增益谱的谱宽最宽 ,获得了增益谱的表达式 ;三阶色散对调制不稳定性不起作用 ;自变陡效应使增益谱的谱宽变窄 ,振幅的增长速度减漫 ;拉曼效应改变了调制不稳定性的产生区域。     

分立式色散补偿拉曼放大器增益特性及非线性现象研究

分立式色散补偿拉曼放大器具有兼顾色散补偿和信号放大的特点，在通信系统中展现出广阔的应用前景.对反向抽运的C波段色散补偿分立式拉曼放大器的增益谱形状，增益饱和及受激布里渊散射等特性进行了较为详细的实验研究. 关键词： 分立式色散补偿拉曼放大器 增益饱和 受激布里渊散射 斯托克斯波     

Supercontinuum generated in all-normal dispersion photonic crystal fibers with picosecond pump pulses

The supercontinuum (SC) generation in all-normal dispersion (ANDi) photonic-crystal fiber (PCF) pumped by high power picosecond pulses are investigated in this paper. Our results show that an octave SC may be achieved by pumping the ANDi PCF with picosecond pump pulses. However, the PCF length required may have to be lengthened to several tens of centimeters, which is much longer than that with femtosecond pump pulses. The relatively long PCF gives rise to much higher Raman gain and stronger Raman frequency shift compared to those with femtosecond pump pulses, which in turn not only cause a distorted temporal waveform and an un-flattened spectrum, but also severely degrade the coherence of the generated SC.     

高折射率芯Bragg光纤的色散特性研究

应用超格子模型分析了高折射率芯Bragg光纤的色散特性，讨论了Bragg光纤的色散的比例性质以及光纤的芯径、包层周期、填充率与波导色散的关系，并利用这些关系举例实现了Bragg光纤在1.55μm附近的宽带色散平坦. 关键词： Bragg光纤 模式 色散 波导色散     

有源弯曲波导反馈特性的三维时域有限差分法仿真

半导体光放大器的耦合光纤形成的外腔反馈通过引入弯曲损耗得以抑制.通过对半导体光放大器有源波导引入对前、后向光场非对称散射损耗,以前向光场部分损耗为代价,反馈光场能量被分布式地较强辐射.时域有限差分法仿真研究表明,通过优化弯曲有源波导的结构,相对于通常的有源直波导,在相同的材料增益和输入、输出条件下,反馈可以下降10 dB以上.由此可以简化高增益半导体光放大器的器件结构.     

Design of double-coated optical fibers to minimize long-term axial-strain-induced microbending losses

The design of double-coated optical fibers to minimize long-term axial-strain-induced microbending losses is investigated. The microbending loss is dominated by the compressive radial stress at the interface between the glass fiber and primary coating. To know the long-term axial-strain-induced microbending losses in double-coated optical fibers, the stresses in fibers are analyzed by the viscoelastic theory. To minimize these long-term microbending losses, the thickness and Young's modulus of the secondary coating should be decreased if the strength of coating is satisfied. Meanwhile, the Poisson's ratio of the primary coating should be increased, but the Young's modulus of the primary coating and relaxation time of the secondary coating should be decreased. Alternatively, the radius and relaxation time of the primary coating exist their optimum values. The long-term axial-strain-induced microbending losses in single-coated optical fibers are also discussed.     

空气孔辅助光纤的模式截止

光纤的截止波长是光纤设计的重要参量之一。利用全矢量正交函数模型对空气孔辅助光纤的模式截止特性进行了讨论。分析表明：由于光纤包层中存在空气孔,即使不考虑材料色散,包层的有效折射率也与波长有关;包层有效折射率由包层中空气孔的大小和波长决定,与芯子的掺杂浓度无关。在所研究的波长范围之内,与传统的w型光纤类似,在包层中空气孔的相对尺寸d／Λ较大时出现了基模截止现象。d／Λ从0．2到0．9变化时,光纤的各阶模式的截止波长都随之减小;各阶模式的截止波长随d／Λ变化曲线的斜率随模式阶次的升高而降低。     

Fiber Bragg gratings for dispersion compensation in optical communication systems

Dispersion compensating fibers (DCF) are the most widely used technology for dispersion compensation. A DCF without Raman amplification introduces extra loss in the system, thus increasing the need for gain in the discrete amplifiers and degrading the noise performance. The idea to additionally use the DCF as a Raman gain medium was originally proposed by Hansen et al. in 1998. [1] This was quickly followed by Emori et al., who demonstrated a broadband, loss less DCF using multiple-wavelength Raman pumping. [2] DCF is a good Raman gain medium, due to a relatively high germanium doping level and a small effective area. To get sufficient gain with a reasonable pump power, a discrete Raman amplifier has to contain several kilometers of fiber, adding extra dispersion to the system that must be handled in the overall dispersion management. Dispersion compensating Raman amplifiers integrates two key functions: dispersion compensation and discrete Raman amplification into a single component.     

Enhanced Compression of Fundamental Solitons in Dispersion Decreasing Fibers with Negative Third-order Dispersion I.Basic Principles

1　Ｉｎｔｒｏｄｕｃｔｉｏｎ　　Ａｄｉａｂａｔｉｃｃｏｍｐｒｅｓｓｉｏｎｏｆｆｕｎｄａｍｅｎｔａｌｓｏｌｉｔｏｎｓｕｓｉｎｇｄｉｓｐｅｒｓｉｏｎｄｅｃｒｅａｓｉｎｇｆｉｂｅｒｓ(ＤＤＦｓ)ｉｓｃｕｒｒｅｎｔｌｙｏｎｅｏｆｔｈｅｐｒａｃｔｉｃａｌｍｅａｎｓｔｏｏｂｔａｉｎｈｉｇｈ ｑｕａｌｉｔｙｆｅｍｔｏｓｅｃｏｎｄｐｕｌｓｅｓ[1～ 3 ] .Ｆｏｒｐｉｃｏｓｅｃｏｎｄｓｏｌｉｔｏｎｓ[1] ,ｔｈｅｙｃａｎｂｅｉｄｅａｌｌｙｃｏｍｐｒｅｓｓｅｄａｓｔｈｅｙｐｒｏｐａｇａｔｅ ,ｒｅｔａｉｎｉｎｇｔｈｅｉｒｓｏｌ…     

飞秒啁啾孤子在线性色散平坦光纤中的相互作用

采用分步傅里叶方法数值研究了在线性色散平坦光纤反常色散区等幅同相孤子脉冲相互作用受高阶色散、拉曼效应、光纤损耗和啁啾参量C等的影响规律。多孤子脉冲在线性和凸形色散平坦光纤中传输100个孤子周期后仍具有孤子特性。在线性色散平坦光纤,多孤子脉冲相互作用受三阶色散影响较严重,三阶色散使各脉冲产生较大的色散波和线性时延;更高阶色散的影响可以忽略;拉曼效应使脉冲产生较大的非线性时延;啁啾加强了脉冲间相互作用;光纤损耗减弱了脉冲间相互作用。     

光子晶体光纤色散补偿特性的数值研究

利用矢量有效折射率方法对光子晶体光纤（PCF）的色散补偿特性进行了数值模拟，研究发现通过调节光子晶体光纤包层的空气穴节距或空气穴大小可以灵活地设计光子晶体光纤的色散系数D、色散斜率Dslope以及κ值，可以设计在波长1.55μm附近具有较大绝对值的正常色散和负色散斜率的色散补偿光子晶体光纤，使光通信中的普通单模光纤（G.652）或非零色散位移光纤(G.655)在1.55μm低损耗窗口得到较好的色散补偿.数值模拟和分析表明色散补偿光子晶体光纤的研制具有很大的发展潜力. 关键词： 光子晶体光纤 色散 色散斜率 色散补偿     

Enhanced compression of femtosecond pulse in hollow-core photonic bandgap fibers

Compression of chirped free femtosecond pulses in hollow-core photonic bandgap fibers is investigated numerically. The results show that intrapulse stimulated Raman scattering can improve the quality of the compressed pulse. Positive third-order dispersion is the main limitation on the compression of the femtosecond pulse. However, the combined effect of the intrapulse stimulated Raman scattering and the negative third-order dispersion can form still shorter pulses than is possible with intrapulse stimulated Raman scattering alone. We also investigate the influence of width and peak power of input pulse on pulse compression.     

能够补偿二阶偏振模色散的三阶段偏振模色散补偿器

简要分析了偏振相关色散对光通信系统性能的影响,提出了一种三阶段高阶偏振模色散补偿方案,从理论上分析了它同时补偿偏振相关色散和偏振主态旋转的可能性,并提出了其可能存在的两种工作方式.通过数值模拟与两阶段补偿方案进行了性能比较,其偏振模色散容限比两阶段补偿提高约17%个比特周期 关键词： 光通信 光偏振 光纤色散     

Polarization-Dependent Gain in Raman Fiber Amplifiers with Depleted Pumps

Polarization-dependent gain in a Raman fiber amplifier in the depleted pump regime is investigated. Numerical investigations are realized and show that gain fluctuations are highly reduced when signal and pump interactions allow pump depletion.     

Enhanced Compression of Fundamental Solitons in Dispersion Decreasing Fibers with Negative Third-order Dispersion Ⅱ. Effects of Fiber Characteristics and Initial Soliton Width

1　Ｉｎｔｒｏｄｕｃｔｉｏｎ　　Ｃｏｍｐｒｅｓｓｅｄ ｐｕｌｓｅｓｆｒｏｍｄｉｓｐｅｒｓｉｏｎ ｄｅｃｒｅａｓｉｎｇｆｉｂｅｒｓ[1] (ＤＤＦｓ)ｈａｖｅａｐｐｌｉｃａｔｉｏｎｓｉｎｔｉｍｅ ｄｉｖｉｓｉｏｎ ｍｕｌｔｉｐｌｅｘｅｄｏｐｔｉｃａｌｃｏｍｍｕｎｉｃａｔｉｏｎｓａｔｒａｔｅｓａｓｈｉｇｈａｓ 1Ｔｂｉｔ/ｓ[2 ] ,ｉｎａｌｌ ｏｐｔｉｃａｌｓａｍｐｌｉｎｇｓｙｓｔｅｍｓ[3] ,ａｎｄｉｎｓｕｐｅｒｃｏｎｔｉｎｕｕｍｇｅｎｅｒａｔｉｏｎ[4] .Ｇｅｎｅｒａｔｉｏｎｏｆｐｅｄｅｓｔａｌ ｆｒｅｅｐｕｌｓｅｓｏ…     

Modulation instabilities in randomly birefringent two-mode optical fibers

Modulation instabilities in the randomly birefringent two-mode optical fibers(RB-TMFs) are analyzed in detail by accounting the effects of the differential mode group delay(DMGD) and group velocity dispersion(GVD) ratio between the two modes, both of which are absent in the randomly birefringent single-mode optical fibers(RB-SMFs). New MI characteristics are found in both normal and anomalous dispersion regimes. For the normal dispersion, without DMGD,no MI exists. With DMGD, a completely new MI band is generated as long as the total power is smaller than a critical total power value, named by Pcr, which increases significantly with the increment of DMGD, and reduces dramatically as GVD ratio and power ratio between the two modes increases. For the anomalous dispersion, there is one MI band without DMGD. In the presence of DMGD, the MI gain is reduced generally. On the other hand, there also exists a critical total power(Pcr), which increases(decreases) distinctly with the increment of DMGD(GVD ratio of the two modes) but varies complicatedly with the power ratio between the two modes. Two MI bands are present for total power smaller than Pcr, and the dominant band can be switched between the low and high frequency bands by adjusting the power ratio between the two modes. The MI analysis in this paper is verified by numerical simulation.