光纤通信系统中偏振模色散自适应补偿实验研究

成功地研制了光纤通信系统偏振模色散的自适应补偿实验系统.实验中采用特定频率分量功率取样作为反馈信号,采用一种名为PSO(Particle Swarm Optimization)的优化方法作为反馈控制算法.偏振模色散的补偿量达30 ps,自动跟踪补偿时间为1～2 s,实现了准实时自动跟踪补偿.     

40 Gb/s光时分复用系统中两级偏振模色散自适应补偿实验研究

偏振模色散效应严重制约着长距离高速光纤通信的发展，偏振模色散的自适应补偿成为光通信领域研究的焦点。利用两阶段偏振模色散补偿器，采用6个自由度的粒子群优化算法(PSO)，通过在线监测搜索光纤链路信号的偏振度极值作为反馈控制信息，在40Gb／s归零码高速光纤传输链路中成功实现了ms量级的偏振模色散自适应补偿。补偿前后采用庞加莱球法测量光纤链路中偏振模色散量，测量结果表明在信号中心波长1560．5nm处，差分群时延补偿前后测量值分别为21ps和1．3ps，而二阶偏振模色散补偿前后测量值分别为266ps^2和43．5ps^2。补偿后实验链路中的一阶和二阶的偏振模色散同时得到不同程度的补偿，并且系统的总的功率代价在误码率为10^-9时小于1dB。     

偏振模色散动态补偿中色度色散影响的研究

分析了色度色散(CD)对偏振模色散(PMD)动态补偿中偏振度(DOP)反馈的影响，模拟和实验验证了2．5Gb／s和10Gb／s非归零调制系统中光信号偏振度特性和系统误码率特性。表明有色度色散作用时信号偏振度值比仅受偏振模色散作用时要大．但误码率随色度色散量增加先轻度好转后就逐渐变差．偏振度值将不能如实反映偏振模色散对系统性能的影响。且信号两正交偏振分量间能量差别越小或差分群延迟越大，上述两种情况下信号偏振度值偏离就越远。这种偏离还随系统速率和色度色散量的增加而加剧。进一步探讨了实际偏振模色散补偿中减轻色度色散影响的措施，表明当系统中同时存在偏振模色散和色度色散影响时，必须在基于偏振度反馈的偏振模色散补偿前完成色度色散补偿。     

40Gb/s光时分复用传输光纤光栅补偿色散研究

用精密扫描掩模法写入宽阻带啁啾光纤光栅,掩模板背面两端各10％长度处镀有按4阶高斯函数透过率的膜,写入的啁啾光栅的时延纹波最大值为20ps。为减少写入光纤光栅的偏振模色散,研制了新的低偏振模色散光纤光栅补偿写入法。采用补偿写入法前的平均微分群时延为9．1406 ps;采用补偿写入法后的平均微分群时延为0．1521 ps。并利用低偏振模色散光纤光栅对40Gb／s光时分复用系统在普通G．652光纤传输122km的色散进行了补偿实验,功率代价为1．5dB。     

高双折射光子晶体光纤偏振模色散测量

对一种高双折射光子晶体光纤的偏振模色散进行了测量.实验用26 m长光子晶体光纤使皮秒光脉冲的两个正交偏振模产生了108 ps时延.运用脉冲时延法和固定分析仪法对这种高双折射光子晶体光纤的偏振模色散进行了实验测量，测量得到其偏振模色散参量可达4154 ps/km，对应的模式双折射度为1.25×10－3.这种新型的高双折射光纤可用于补偿光纤通信系统中的偏振模色散.     

高速相干光通信系统中残留色散均衡器研究

在高速相干光通信系统中,完全使用电子色散补偿时会引入均衡增强相位噪声.本文提出在已有10Gbit/s光纤通信链路上使用电子色散补偿来补偿残留色散的混合色散补偿方案,实现了特定通道100Gbit/s以上高速数据传输.使用虚拟光学仪器软件仿真了在112Gbit/s相干光通信系统中,分别采用有限脉冲响应均衡器和重叠频域均衡器对现有光纤信道进行残留色散补偿后的系统性能.仿真结果表明:相同的抽头长度下,有限脉冲响应均衡器相比重叠频域均衡器有更好的残留色散补偿能力,并且有限脉冲响应均衡器均衡性能更稳定而且计算复杂度更低.因而,有限脉冲响应均衡器相较于重叠频域均衡器更适于混合色散补偿.     

高速光通信系统中光纤光栅色散补偿研究

通过对光栅制作过程的优化设计，解决了光纤光栅温度稳定性、纹波系数、带宽、偏振模色 散补偿等关键技术，所制作光纤光栅已经达到温度系数小于00005 nm/℃，带宽大于14 nm，纹波系数小于50 ps，色散量超过 -1000 ps/nm的先进水平. 采用琼斯矩阵本征值法较 精确地测量了光栅的偏振模色散，并对其进行了补偿，光纤光栅色散补偿器的偏振模色散由 补偿前的91406 ps改善为补偿后的01521 ps. 在此基础上，成功地建立了一个稳定可靠 、速率为40 Gb/s，传输链路为122 km G 关键词： 高速光通信系统 普通单模光纤 光纤光栅 色散补偿     

偏分复用系统中偏振模色散补偿与偏分解复用一体化方案

本文建立了偏分复用系统中偏振模色散与信号偏振态变化引起信道串扰的数学模型, 分析了偏振模色散对偏分复用信道射频功率的影响, 并提出了适用于偏分复用系统的光域偏振模色散补偿与偏分解复用同时进行的方案: 用信道的射频功率作为反馈控制信号, 监测链路中偏振模色散和偏振态变化引起的信道串扰的大小, 用改进的粒子群优化算法对偏振控制器进行自适应控制, 同时完成偏振模色散补偿与偏分解复用. 在112 Gb/s偏分复用-差分正交相移键控(PDM-DQPSK)传输系统中仿真验证了该方案的有效性. 结果表明该方案可以使112 Gb/s-PDM-DQPSK传输系统完成自适应偏分解复用的同时, 在1 dB的光信噪比代价下, 使系统对偏振模色散的容忍度提高20 ps. 关键词： 偏分复用系统 信道串扰 偏振模色散 偏分解复用     

粒子群优化算法在自适应偏振模色散补偿中的性能研究

反馈控制算法是偏振模色散的自适应补偿器的关键组成部分,将粒子群优化算法(PSO)引入到偏振模色散自适应补偿系统中。该算法的优点是具有快速收敛到全局最佳值的能力、避免搜索陷入局部极值的能力、抗噪声能力和多自由度控制能力。理论上分析了粒子群优化算法的两个分类———全局邻居结构粒子群优化(GPSO)和局部邻居结构粒子群优化(LPSO)在搜索全局最佳值方面的能力优劣,给出了局部邻居结构粒子群优化算法成功率达100%的三种邻居拓扑结构。实验表明:在补偿一阶偏振模色散时,全局邻居结构和局部邻居结构搜索全局最佳的成功率都能满足要求,全局邻居结构算法收敛速度快。而在补偿二阶偏振模色散时,全局邻居结构成功率降低,而局部邻居结构仍可以满足要求。     

用于高阶偏振模色散补偿的高效动态补偿器

基于基本偏振态模型,采用三双折射元补偿结构,提出一种用于补偿高速率光纤通信系统中的偏振模色散的可行方案.此方案在一阶偏振模色散补偿的基础上,仅增加了对两个参量的控制,即可对高阶偏振模色散进行补偿,并且高阶补偿过程的参量控制完全独立于一阶补偿过程,极大的提高了偏振模色散的动态补偿效率.数值模拟结果表明,此方案的补偿效果也是显著的.     

Electronic compensator for 100-Gb/s PDM-CO-OFDM long-haul transmission systems

We study an electronic compensator (EC) as a receiver for a 100-Gb/s polarization division multiplexing coherent optical orthogonal frequency division multiplexing (PDM-CO-OFDM) system without optical dispersion compensation.EC,including electrical dispersion compensation (EDC),least squares channel estimation and compensation (LSCEC),and phase compensation (PC),is used to compensate for chromatic dispersion (CD),phase noise,polarization mode dispersion (PMD),and channel impairments,respectively.Simulations show that EC is highly effective in compensating for those impairments and that the performance is close to the theoretical limitation of optical signal-to-noise rate (OSNR),CD,and PMD.Its robustness against those transmission impairments and fiber nonlinearity are also systematically studied.     

10 Gb/s光通信传输系统中一阶PMD自适应补偿实验

在10 Gb/s归零码(RZ)光通信传输链路中成功地搭建一阶PMD自适应补偿的实验系统,补偿量29 ps,跟踪补偿时间在1 s以内,补偿效果明显.     

Impact of polarization dependent loss on degree of polarization as feedback signal of polarization mode dispersion

Polarization dependent loss (PDL) has been recognized as a critical issue because various inline optical components may have nonnegligible PDL effect that interacts with polarization mode dispersion (PMD).We investigated the impact of PMD-PDL interaction on degree of polarization (DOP), which is the most commonly used feedback signal in PMD compensation. The simulation results of a 40-Gb/s NRZ code optical transmission system show that the maximum PMD increases from approximately 40 ps to more than 45 ps, while minimum DOP declines from approximately 0.6 to approximately 0.2. The interaction of PMD and PDL also induces residual PMD underestimation of 5-8 ps, which causes degradation of PMD compensation performance.     

Joint scheme for symbol,sampling clock,and carrier frequency synchronization in PDM-CO-OFDM system beyond 100 Gb/s

We propose a joint scheme for symbol, sampling clock, and carrier frequency synchronization in a polarization division multiplexing coherent optical orthogonal frequency division multiplexing （PDM-CO-OFDM） system. Unlike other existing algorithms designed for specific impairment, the scheme can estimate and compensate for the interactional synchronization errors effectively without extra training overhead by building a comprehensive error model. The simulation shows that symbol synchronization error and sample timing error can be corrected by channel equalizer, and the estimation ranges of sampling frequency offset and normalized carrier frequency offset are about （-2000, 2000） ppm, and （-0.04 （-3.5）, 0.04 （3.5）） Ghz, respectively.     

Simultaneously compensating tunable CD and adaptive PMD using two different nonlinearly chirped fiber Bragg gratings

Experimental research of simultaneous tunable chromatic dispersion(CD)and adaptive polarization mode dispersion(PMD)compensations in optical fiber communication system was reported.Two different nonlinearly chirped fiber Bragg gratings fabricated through the equivalent chirp technology were adopted in the experiment.One of the gratings was used as CD compensator,with a tunable dispersion range from 300 to 600 ps/nm.The other made of photosensitive polarization maintaining fiber was used as a tunable delay line of PMD compensator,which provided a varying amount of differential group delay(DGD)from 40 to 110 ps.Our experiment was operated at 10-Gb/s non-return-to-zero(NRZ)system and the results showed that the eye pattern recovery is excellent after both PMD and CD are compensated.Especially,the power penalty at a bit error rate(BER)of 10-9 is about 1 dB.     

基于偏振模色散矢量的偏振模色散补偿方案的研究

在研究局部偏振模色散矢量与整体偏振模色散矢量关系的基础上，从理论上得到完全补偿偏振模色散的关系，结论是至少利用两段保偏光纤才能完全补偿。提出了基于偏振模色散矢量的偏振模色散补偿方案和调节控制的算法原理及改进的方向。这些结果对正确进行偏振模色散补偿是很有帮助的。     

相敏光放大器对光纤偏振模色散进行补偿的探讨

根据耦合非线性薛定谔方程,在考虑偏振模色散的情况下,采用数值方法仿真了含有相敏光放大器的高速光纤传输系统性能,获得了一组优化参量.仿真结果表明,相敏光放大器对于光纤偏振模色散的影响有一定的补偿作用.     

Least mean square error difference minimum criterion for adaptive chaotic noise canceller

The least mean square error difference （LMS-ED） minimum criterion for an adaptive chaotic noise canceller is proposed in this paper. Different from traditional least mean square error minimum criterion in which the error is uncorrelated with the input vector, the proposed LMS-ED minimum criterion tries to minimize the correlation between the error difference and input vector difference. The novel adaptive LMS-ED algorithm is then derived to update the weights of adaptive noise canceller. A comparison between cancelling performances of adaptive least mean square （LMS）, normalized LMS （NLMS） and proposed LMS-ED algorithms is simulated by using three kinds of chaotic noises. The simulation results clearly show that the proposed algorithm outperforms the LMS and NLMS algorithms in achieving small values of steady-state excess mean square error. Moreover, the computational complexity of the proposed LMS-ED algorithm is the same as that of the standard LMS algorithms.     

Wideband all-order polarization mode dispersion compensation via pulse shaping

We demonstrate the application of ultrafast pulse-shaping techniques for experimental wideband all-order polarization mode dispersion (PMD) compensation, for the first time to our knowledge. PMD is treated as arbitrary variations of state of polarization and phase versus wavelength, in an all-order sense. Consequently, two pulse shapers are implemented in a serial manner to compensate for the polarization and the phase spectra independently. We report compensation of subpicosecond pulses (14 nm bandwidth around 1550 nm) that are anomalously spread to more than 2 ps as a result of PMD. This PMD compensation scheme can potentially be a powerful and cost-effective solution for fiber optic telecommunication networks.