高阶孤子在色散渐减光纤环中的传输特性研究

研究了高阶孤子在对称结构和不对称结构的色散渐减光纤环形镜的脉冲传输特性,比较了不同耦合系数下的色散渐减光纤环形镜的开关性能及脉冲压缩性能.得出了使色散渐减光纤环具有良好脉冲输出的耦合器系数范围,对实验中参数的选取有一定的指导意义.发现不对称结构光纤环形镜亦能产生无基座超短脉冲.     

取样啁啾光纤光栅的时延抖动抑制

研究了用于多通道色散补偿器的取样啁啾光纤光栅时延抖动问题,分析了产生时延抖动的腔效应及抑制时延抖动的切趾技术,分析、比较了切趾前后取样啁啾光纤光栅的时延抖动情况,研究结果表明:取样啁啾光纤光栅的时延抖动与其折射率包络调制形成的外腔效应有关,与取样调制形成的多腔效应无关,对取样啁啾光纤光栅进行包络切趾能够有效地抑制时延抖动.     

偏振模色散和时延抖动对啁啾光纤光栅色散补偿特性的影响

对存在偏振模色散(PMD)和群时延(GD)抖动的非理想线性啁啾光纤光栅的色散补偿特性进行了研究。实验测量了啁啾光纤光栅的群时延谱和偏振模色散光谱，理论分析和实验测量表明，啁啾光纤光栅差分群时延(DGD)抖动与其时延抖动密切相关。通过数值模拟方法，计算了线性啁啾光纤光栅偏振模色散眼图代价与入射到啁啾光纤光栅色散补偿器的光信号的偏振方向的关系，计算结果表明在使用啁啾光纤光栅色散补偿器时应对光信号的偏振方向进行调整，以获得最佳补偿效果。另外结合实验数据，模拟计算并讨论了非理想线性啁啾光纤光栅群时延抖动和偏振模色散引起的信号的展宽和脉冲形状的劣化。     

色散平坦光子晶体光纤色散和非线性特性研究

采用矢量波束传播法(BPM) 对不同结构参量的光子晶体光纤的色散和非线性特性进行数值分析,计算色散平坦光子晶体光纤的参量色散系数D,有效模场面积 和非线性系数 。分析D, 与色散平坦光子晶体光纤结构参量空气孔间距 、空气孔直径 之间的关系。分析结果表明,调节色散平坦光子晶体光纤的结构参量可以灵活地调整色散和非线性特性。得到的色散平坦光子晶体光纤在1300nm到1600nm波长范围内,色散值仅在-1.5 左右,非线性系数都大于19 。     

Dispersion compensation by differential time delay

A technique for optical pre- or postdistortion in order to compensate for fiber dispersion is discussed theoretically, The dispersion compensation device is based on differential time delay for the upper and the lower sideband of the modulated signal. The proposed scheme is primarily intended for high bit rate (>10 Gbit/s) time division multiplexed transmission, and in an ideal case the transmitting distance could be enhanced by a factor of 4 in a dispersive limited system. With more realistic demands on the dispersion compensation device, the gained distance is in the order of 2.5     

基于色散器件的光真延时线中的色散限制

利用强度-频率混合调制模型研究了基于色散器件的光真延时线中色散导致的延时误差的变化规律.基于对延时误差的分析,研究了色散对系统性能的限制,为光真延时线的设计提供了理论参考.     

Narrow-waisted Gaussian beam discretization for short-pulseradiation from one-dimensional large apertures

We develop a Gabor-based Gaussian beam (GB) algorithm for representing two-dimensional (2-D) radiation from finite aperture distributions with short-pulse excitation in the time domain (TD). The work extends previous results using 2-D frequency-domain (FD) narrow-waisted Gaussian beams. The FD algorithm evolves from the rigorous Kirchhoff integration over the aperture distribution, which is then parameterized via the discrete Gabor basis and evaluated asymptotically for high frequencies to furnish the GB propagators to the observer. The TD results are obtained by Fourier inversion from the FD and yield pulsed beams (PB). We describe the resulting TD algorithm for several aperture distributions, ranging from simple linearly phased (linear delay) to arbitrary time delay profiles; the latter accommodate the important case of focusing TD aperture fields. For modulated pulses with Gaussian envelopes, we compute accurate closed form analytic solutions, which have been calibrated against numerical reference data. Our results confirm that the previously established utility of the Gabor-based narrow-waisted FD-GB algorithm for radiation from distributed apertures remains intact in the TD     

三阶色散对双芯光纤孤子传输的影响

对双芯色散位移光纤中三阶色散影响下光孤子的传输特性进行了数值计算．结果表明，三阶色散引起孤子出现线性时延，也引起同相孤子之间出现随传输距离线性增长的相互排斥，而且这两种特征是独立存在的．此外，耦合作用依传输距离线性地同时影响着二者．     

偏振模色散统计特性的研究

利用动态方程研究了偏振模色散矢量的统计特性 ,分别用统计系综和频率系综两种方法进行数值模拟。数值结果表明 ,统计系综和频率系综两种方法的结果一致。在大归一化距离条件下 ,均方根时延的平方随归一化距离线性变化 ;偏振模色散矢量的各个分量服从高斯分布 ,差分群时延服从麦克斯韦分布 ;偏振模色散矢量弥散于整个邦加球     

掺铒光纤放大器的非线性色散效应

给出一种模型来考虑非线性色散对光通信系统的影响。数值结果表明 ,考虑非线性色散时 ,光脉冲的传播速度比不考虑非线性色散时的传播速度要快 ,而脉冲展宽是一样的     

光纤光栅色散效应对相控阵天线影响的研究

研究光纤光栅色散效应对基于光栅的相控阵天线的影响,该相控阵天线基于典型的离散光纤光栅阵列的实时延迟线结构。分析表明,单边带调制方式可以有效地克服色散效应对所恢复的微波信号幅度的影响。但光纤光栅色散效应对所恢复的微波信号相位的作用仍影响实时延迟线的性能,从而改变天线阵列最大辐射方向。通过选择合适的天线元之间的距离以及提高相邻通道所对应的光纤长度差可以降低光纤光栅色散效应的影响。     

DISPERSION COMPENSATION CFBG IN100km 10Gbit／s RECIRCULATING SYSTEMS

A 10Gbit/s recirculating system is configured with Chirped Fiber Bragg Grating (CFBG) for the dispersion compensation. For the first time, the transmission distance in the loop reaches 1000km with bit error rate of 10-9. The effect of the group delay ripple of the fiber grating is also investigated in the recirculating systems, and it is shown that the transmission distance is limited to 4 cycles (4×167.1km ) in the loop with the power penalty fluctuation below 1.0dB. Thus the group delay ripple should be reduced to allow for the wavelength drift of±5GHz. At the end of this letter, the principles are given for designing long haul recirculating systems with dispersion compensation CFBG.     

Time-Delay Limits Set by Dispersion in Magnetostatic Delay Lines (Short Papers)

Analysis and experiments show the extreme dispersion of magnetostatic delay lines. A suitable parameter to characterize the amount of dispersion present has been found to be the maximum output energy contained in a time interval equal to the input pulse duration. The time occurrence of this maximum value gives a convenient measure of the group delay. The pulse shape and energy content versus delay have been determined both theoreticaly and experimentally for axially magnetized circular rods. The results show that delays beyond two to three times the input pulse duration cannot be obtained with more than 50 percent of the output energy contained within the original pulse duration.     

负色散镜的设计、制备及在掺钛蓝宝石激光谐振腔内的使用

根据钛宝石激光器的要求设计了性能优良的两种负色散镜(NDM1和NDM2)。NDM1同时引入啁啾效应和G-T效应产生大的群延迟色散量以减少光在负色散镜上的反射次数。NDM2仅引入G-T效应产生较小的群延迟色散以补偿腔内自相位调制带来的部分啁啾。选用离子束溅射法制备了这两种负色散镜。用分光光度计测试了它们的透射率。结果表明,所制备的负色散镜的性能与设计性能非常接近。使用这两种负色散镜进行掺钛蓝宝石激光谐振腔内色散补偿实现了飞秒脉冲锁模,获得了15 fs的超短脉冲。     

负折射介质中非线性色散效应对调制不稳定性的影响

研究了负折射介质中非线性色散效应对调制不稳定性的影响,揭示了若干新的不稳定性现象。得到了有任意高阶线性与非线性色散效应情形下调制不稳定性增益谱的表达式,结果表明:所有偶次非线性色散不但会影响原来的不稳定性,而且可能会导致新的不稳定性区域;而所有的奇次非线性色散将始终抑制调制不稳定性,且与其符号的正负无关。进一步研究了由色散磁导率所诱导的二阶非线性色散效应对调制不稳定性的影响。研究发现它不但能使在常规介质中不可能出现的调制不稳定性现象也能出现,而且可能会导致在无限带宽的调制频率范围内发生新的不稳定性现象,且其增益值将随调制频率的增大而单调增大。     

光通讯器件中F-P标准具型色散研究

推导了光通信系统中任意两平行光学表面间由多光束干涉引起的群延迟色散(GDD)的表达式;分析了GDD的变化规律,包括周期性、平方律特性和对表面反射率的依赖关系。同时指出通过法布里-珀罗(F-P)光学标准具后的反射波色散特性与透射波色散特性间的差异,对反射波色散中出现的奇异性进行了讨论。     

准线性光传输系统色散管理方案的研究

推导了准线性光传输系统中受信道内四波混频、信道内交叉相位调制等信道内非线性效应影响的非线性传输方程,搭建了可构成多种色散管理方案的仿真传输链路,对10Gb/s、40Gb/s、100Gb/s、160Gb/s等四种不同速率的准线性光传输系统的色散管理方案进行了数值分析,分析了幅度抖动与定时抖动的关系,幅度抖动与系统Q值的关系,以及脉冲初始功率与系统Q值的关系。首次得到了单信道准线性光传输系统的最优色散管理方案与系统传输速率相关,并且随着系统传输速率的增加,前色散补偿部分的比例应逐步减少、后色散补偿部分的比例应逐渐增加并可量化的结论。     

基于材料补偿的线性色散组合棱镜研究

作为传统的分光器件,棱镜的非线性色散缺陷限制了其在精密光谱仪器中的应用。从分析棱镜非线性色散产生的本质出发,建立了材料的色散模型,提出了一种线性色散组合棱镜设计方法。使用非线性系数T1和T2相近、线性系数V相异的两种材料,通过控制组合棱镜的参数和光线入射角可获得线性色散。最后通过建立线性色散组合棱镜的评价指标,对设计结果进行了科学、合理的评价,验证了设计理论的正确性。研究发现,组合棱镜能够有效改善棱镜的非线性色散缺陷,其改善程度依赖于两种材料的绝对非线性系数P。当P<0.01时,组合棱镜可获得线性色散,其色散曲线的非线性(Nonlinear, NL)优于5%。     

Some Experimental Results on In-Band Amplitude Dispersion and a Method for Estimating In-Band Linear Amplitude Dispersion

In-band amplitude measurement was conducted on a 63.4 km test path with an oversea section (normal reflection point was on the ground), using a frequency band from 4440 to 4500 MHz. Results on peak-to-peak amplitude dispersion and linear amplitude dispersion were obtained for both nondiversity and idealized space diversity receptions. Potential improvements by space diversity in terms of reductions of amplitude dispersion were remarkable in the large amplitude dispersion region. An analysis of the in-band amplitude pattern was made in order to identify which multiray is most responsible for amplitude dispersion during multipath fading. The main cause of amplitude dispersion was found to be waves irregularly reflected from the sea surface and waves reflected from the ground, with a long delay but small amplitude. A frequency correlation function for received power, which is necessary for estimating linear amplitude dispersion, was derived theoretically, for the three-path model. The theoretical frequency correlation agrees well with that measured on this path.     

偏振模色散对单模光纤的影响

单模光纤的偏振模色散是两个相互正交偏振模之间的差分群时延 ,是高速率数字系统性能的限制因素之一 ,我们必须深刻理解偏振模色散的理论 ,才能在施工时采取相应的措施 ,保证光纤系统的施工质量