三阶色散对光纤中基孤子脉冲传输的影响

通过数值求解非线性薛定谔方程,研究了三阶色散效应对基孤子脉冲在单模光纤中传输的影响.结果表明,在三阶色散作用下,基孤子脉冲在传输过程中被展宽,峰值能量逐渐减小,脉冲形状发生畸变,脉冲的中心偏向一侧,并形成非对称的拖尾振荡结构;当与二阶色散共同作用时,三阶色散引起的脉冲振荡会变缓.考虑非线性效应后,在一定程度上补偿了由于色散效应导致的峰值功率的减小,同时抑制了非对称拖尾结构的产生.     

弱非线性在零色散波长处对光信号的影响

文章得出在零色散波长处二阶色散为零时，光信号在弱非线性与三阶色散的共同作用下的频域级数解，得出了高斯脉冲在光纤中传输时的近似频域表达式，并利用数值积分方法出时域波形与脉冲展宽因子演化图。     

采用单环微谐振器的光滤波器特性及其局限性

对采用单环微谐振器的光滤波器的特性进行了分析。在给出的传递函数和相关特性公式基础上，分析了出／入环光耦合系数与通带带宽和通带消光比间的关系，指出了它们之间、以及与自由谱范围间存在的相互约束；分析并给出了单环光滤波器的通带带宽比例，带宽比例值不依赖于任何器件结构参数，是限制单环微谐振器作为实用光滤波器的主要因素；分析了存在于微环中光的损耗对单环光滤波器输出的影响，小的光损耗即会导致滤波响应的巨大衰减，大的光损耗则更是会导致带宽的展宽和带宽比例值的增大。     

飞秒激光脉冲在大气中的色散及补偿

卫星飞秒激光测距理论上可达到亚微米量级的测距精度,但飞秒激光脉冲在大气中传输时由色散导致的脉冲展宽显著,会使测距精度下降。为补偿飞秒激光脉冲在大气中的色散需对其色散量进行定量计算。推导了飞秒激光脉冲在大气中的群速度色散和脉冲展宽公式,表明脉冲展宽程度和群速度色散及传输距离有关;中心波长相同的飞秒激光脉冲脉宽越窄色散越严重,而当脉宽相同时,中心波长越短色散越严重。计算比较了大气和BK7玻璃的群延时、群速度色散和三阶色散。卫星激光测距系统应采用中心波长较长的1 550 nm的飞秒激光脉冲,脉宽应适当选取。由于飞秒激光色散严重,提出了采用单模光纤序列进行粗补偿和采用光栅对进行精密补偿的两种补偿相结合的方式对其色散进行补偿。     

五阶非线性和高阶色散作用下超高斯脉冲的传输特性

从非线性薛定愕方程出发,用变分法得出了描述锐度因子为不同自然数的超高斯脉冲在光纤色散(高阶和二阶)和非线性(三阶和五阶)作用下传输的微分方程组,用龙格-库塔算法对微分方程组进行数值求解,结果表明对于给定的较小的光纤色散和非线性系数,都存在特定的三阶和五阶非线性系数使非线性有效地对高阶和二阶色散给脉冲传输造成的展宽影响加以补偿,此时超高斯脉冲在光纤以近似保形的状态稳定传输。当色散系数与非线性系数之比太大时脉冲将被无限展宽。     

啁啾光脉冲在高阶色散控制光纤链中的稳定传输

基于一种二阶和三阶色散补偿的光纤级联系统模型 ,用数值法对啁啾皮秒光脉冲作了传输模拟。结果表明 ,完全补偿的高阶色散控制系统消除了三阶色散所引起的脉冲边沿部的振荡 ,减弱了脉冲峰的时间移动 ;另外 ,在确定的配置下 ,给输入脉冲附加一最佳的频率啁啾 ,可使得色散控制孤子稳定传输。脉冲宽度和啁啾以及光强度都围绕在初始值附近波动 ,在每个补偿周期末端 ,基本恢复到初始值 ;最佳啁啾的选取与二阶色散的配置有关 ,与三阶色散的配置无关 ;文中画出了 10 0Gbit/s码率的 64位随机高斯光脉冲序列在完全补偿系统中传输 10 0 0 0km后的眼图。由清晰的眼图可知 ,这种完全补偿系统减弱了脉冲之间的相互作用     

色散管理传输系统中克尔效应对偏振模色散的补偿研究

光纤的随机双折射效应可导致脉冲无规展宽即偏振模色散(PMD)。在零路径色散管理孤子传输系统中，二阶色散和三阶色散效应均被完全补偿，克尔效应成为一种有害因素会使脉冲变窄，但是当光纤的随机双折射被考虑时，克尔效应正好与PMD相互抵消，使光脉冲准稳定传输，不同的光纤偏振模色散参数分别对应不同的最佳系统功率。此外，如果考虑不同偏振方向的损耗差异，则即使在最佳匹配条件下，微小的偏振损耗差异也可产生很大的脉宽波动。因此，偏振相关损耗是影响脉冲传输质量的相当重要的因素，不论在理论计算还是在工程设计中都应当认真考虑。     

单模光纤反常色散区零色散波长附近的啁啾演变

当单模光纤的反常色散区二阶，三阶色散同时存在时，首次推出了群速度色散致啁啾的解析表达式，并讨论了啁啾演变过程。利用数值方法，模拟了零色散波长附近群速度色散效应与自相位调制效应共同作用时啁啾的演变。结果表明，三阶色散会导致脉冲铅的畸变。     

分布式光纤放大器的色散分析

在考虑了增益介质的色散、非线性效应、增益以及损耗后,推导出超短光脉冲在分布式光纤放大器中的基本传输方程,采用分步傅里叶变换法数值模拟了皮秒光脉冲的放大传输状态,重点分析了群速度色散和三阶色散对光脉冲特性的影响。     

超高速光通信中超窄光脉冲高阶色散扰动分析

针对应用于超高速光通信网络中的超窄光脉冲传输问题,理论分析并数值计算了光纤中的三阶色散与四阶色散对超窄脉冲波形的影响,得到了三阶色散影响导致光脉冲前沿产生形变,后沿基本保持不变,四阶色散导致脉冲急剧展宽以及光谱出现旁瓣的结论.     

Ultrashort optical pulse transmission characteristics of verticallycoupled microring resonator add/drop filter

The ultrashort optical pulse transmission characteristics of a vertically coupled microring resonator (VCMRR) filter were measured at 1.55 μm wavelength, and the transmission capacity per channel was evaluated. The pulsewidth at the output was measured to be 3.4 ps, when 1.2 ps input pulse with a sech pulse shape from a fiber laser was incident on the microring resonator filter with a fullwidth at half-maximum (FWHM) of 0.75 nm (94 GHz). From this result, the maximum transmission capacity of the filter was estimated to be approximately 50 Gb/s. The pulse broadening through the filter was theoretically analyzed, and it was confirmed that the pulse broadening evaluated from the bandwidth of the filter spectrum response were in good agreement with the measured results     

Polymer microring coupled-resonator optical waveguides

We present measurements of the transmission and dispersion properties of coupled-resonator optical waveguides (CROWs) consisting of weakly coupled polymer microring resonators. The fabrication and the measurement methods of the CROWs are discussed as well. The experimental results agree well with the theoretical loss, waveguide dispersion, group delay, group velocity, and group-velocity dispersion (GVD). The intrinsic quality factors of the microrings were about 1.5/spl times/10/sup 4/ to 1.8/spl times/10/sup 4/, and group delays greater than 100 ps were measured with a GVD between -70 and 100 ps/(nm/spl middot/resonator). With clear and simple spectral responses and without a need for the tuning of the resonators, the polymer microring CROWs demonstrate the practicability of using a large number of microresonators to control the propagation of optical waves.     

Linearized microring-loaded Mach-Zehnder modulator with RF gain

A linearized modulator based on the Mach-Zehnder interferometer (MZI) loaded with a second-order allpass microring resonator is proposed and analyzed. The device is shown to exhibit much smaller intermodulation distortion than standard Mach-Zehnder modulators, thus greatly enhancing the device dynamic range. Gain effect associated with the microring resonance results in a modulator transfer function with high slope efficiency and large RF gain. Moreover, combined with the use of a highly electrooptic polymer, the high slope efficiency allows for the possibility of realizing modulators with subvolt drive voltage. The detrimental effect of loss in the microring resonators on device performance is also investigated and a design approach to mitigate its effect is presented. The proposed modulator can be linearized to any arbitrary nth order by loading the MZI with a higher order allpass microring resonator.     

Long-haul WDM transmission using higher order fiber dispersionmanagement

We propose a fiber dispersion management scheme for large-capacity long-haul wavelength division multiplexing (WDM) transmission systems that considers not only second- but also third-order dispersion characteristics using transmission fibers with opposite dispersion signs. It eliminates the waveform distortion of WDM signals that originates from the existence of third-order dispersion, which is a constraint placed on WDM capacity in conventional dispersion management, while reducing the interchannel interaction caused by the interplay of fiber nonlinearity and second-order dispersion. Design concept of the scheme is discussed to show the feasibility of using actual fiber parameters. An experimental investigation on transmission performance regarding the signal pulse format, nonreturn-to-zero (NRZ) and return-to-zero (RZ), and interchannel interaction caused by four-wave mixing (FWM) and cross-phase modulation (XPM) is described for optimizing WDM system performance. It is experimentally shown that RZ pulse transmission is possible without significant spectral broadening over a wide wavelength range in dispersion managed fiber spans. Using these results together with a wideband optical amplifier gain-bandwidth management technique, yields long-distance WDM transmission with the capacity of 25×10 Gb/s over 9288 km     

Design and modeling of waveguide-coupled single-mode microringresonators

We discuss a first-order design tool for waveguide-coupled microring resonators based on an approximate solution of the wave propagation in a microring waveguide with micron-size radius of curvature and a large lateral index contrast. The model makes use of the conformal transformation method and a linear approximation of the refractive index profile, and takes into account the effect of waveguide thickness, dispersion, and diffraction. Based on this model, we develop general design rules for the major physical characteristics of a waveguide-coupled microring resonator, including the resonance wavelength, the free spectral range, the coupling ratio, the bending radiation loss and the substrate leakage loss. In addition, the physical model provides leads to alternative coupling designs. We present two examples, one using a phase-matching parallel waveguide with a smaller width than the ring waveguide, and the other using a vertical coupling structure. Both these designs significantly increase the coupling length and reduce or eliminate the dependence on a narrow air gap in a waveguide coupled microring resonator     

Compensation of dispersion in optical fibers for the 1.3-1.6 μmregion with a grating and telescope

The transmission of ultrashort optical pulses over long distances in optical fibers is limited by pulse broadening due to group velocity dispersion. A grating and telescope dispersion compensator with group velocity dispersion of equal magnitude and opposite sign can compensate for the fiber dispersion. The possible benefits of such dispersion compensation in the 1.3-1.6-μm wavelength region are investigated. The results show that compensation of first-order dispersion at 1.55 μm in a fiber with zero dispersion near 1.3 μm is primarily limited by the second-order dispersion of the grating and the telescope compensator. For a wavelength slightly greater than the zero dispersion wavelength, both the first- and second-order group velocity dispersion can be canceled by the grating and telescope dispersion compensator, allowing transmission exceeding 100 Gb/s over 100 km     

串联微环谐振器的光学特性

根据波导耦合方程,导出了串联微环谐振器的传输矩阵,并分析了环数、环间耦合系数以及损耗对串联微环谐振器输出特性的影响。数值模拟表明,串联微环谐振器具有光子带隙的特征。当环数增加时,通带内满足谐振条件的波长数增加;当环间耦合系数增加时,可使通带带宽加宽;通过适当选择环数和环间耦合系数,可以实现滤波和波分复用(WDM)的功能。选用脉冲宽度为50 ps的高斯型激光脉冲注入微环谐振器,发现当环间耦合系数较小时,出射脉冲相对于入射脉冲具有光学延迟的效果,并且随着环数的增加,延迟时间逐渐增大,而当环间耦合系数较大时,光学延迟效果不明显。     

单直波导光学环腔器件的Q值研究

为实现高品质因数Q值的光学环腔器件,采用耦合模理论,仿真得出单直波导光学环腔器件的Q值与自耦合系数的关系曲线.以Si3N4为材料,采用与CMOS工艺相兼容的技术制备了波导宽度为2μm,半径为200μm的Si3N4单直波导光学环腔器件.在相同的制备工艺下,同一芯片中不同光学环腔的传输系数相同,通过设计器件中环腔与直波导的...     

信号流程图理论分析多环谐振滤波器特性

微环谐振腔以其功能多样、结构简洁、集成度高等特点已经成为当前的研究热点。采用多环结构形成的滤波器能够实现在通带内比单环谐振滤波器更为陡峭的滚降、更平坦的峰顶和更好的抑制阻带。利用信号流程图法(SFG)推导了串联耦合和并联耦合两种形式的多环谐振滤波器的系统传递函数公式。在串联结构中,滤波器的输出特性主要受到耦合系数和损耗的影响;在并联结构中,通过优化环间距,从而使下载端输出光谱达到比较好的形状。     

Pulse Delay and Advancement in SOI Microring Resonators With Mutual Mode Coupling

In this paper, we experimentally demonstrate continuously tunable pulse propagation in SOI microring resonators with mutual mode coupling, which is induced by nanosized gratings along the ring sidewalls. In the presence of the mutual mode coupling, dispersion-induced group delay is investigated in single-waveguide and double-waveguide coupled single-ring resonators, respectively. In particular, pulse propagation in the drop channel of a double-waveguide coupled resonator is observed and exhibits continuously tunable delay and advancement features in the experiment. Delayed pulses are also obtained at the reflection port of a single-waveguide coupled resonator due to the existence of backward whispering gallery mode (WGM).