偏振模色散模拟器一阶及二阶偏振模色散统计特性的分析

从光纤的琼斯矩阵模型出发,利用蒙特-卡洛方法对偏振模色散模拟器的统计特性进行了研究.研究结果表明:随着组成模拟器的保偏光纤的段数增加,一阶和二阶偏振模色散的统计分布越接近于理论拟合曲线.比较了两种不同模拟器的组成方法,得到的结果将对模拟器的设计具有实际的指导作用.     

光纤偏振效应导致脉冲展宽的解析模型

在10Gb／s,尤其是40Gb／s以上高速光纤通信系统中,光纤的偏振特性已成为限制系统传输距离的主要因素之一。光纤的偏振效应主要包括偏振模色散和偏振依赖损耗。而脉冲均方根展宽是判断信号传输性能的一个主要物理量。本文讨论了光纤线路偏振模色散与偏振相关损耗的相互作用及对信号脉宽的影响。给出了线路偏振模色散矢量和偏振相关损耗矢量之间的关系式,并基于严格的数学方法,导出了在光纤偏振模色散和偏振相关损耗共同作用下的信号均方根脉宽变化的解析形式,同时考虑了光纤色散,啁啾等。该模型可用于分析高阶偏振模色散和偏振相关损耗,任意线性光纤通信系统脉冲展宽分析。     

A model to characterize the effect of cross phase modulation on polarization in an optical fiber transmission system

This paper presents a model that described the process of inter-influence between cross phase modulation (XPM) and polarization effects such as polarization mode dispersion (PMD) and polarization dependant loss (PDL) in an optical fiber communication system. Previous papers have discussed PMD-PDL and PMD-XPM effects in separate models, but in this work we developed a model that is capable of characterizing and evaluating PMD, PDL and XPM simultaneously. From the model, we found that PMD and PDL can be affected by XPM. The presence of XPM changed the vector directions of PMD and PDL in Stokes space.     

偏振模色散模拟器的特性

通过对微分群时延差(DGD)统计特性和偏振模色散(PMD)矢量自相关函数的数值模拟，分析比较了目前常用的三种PMD模拟器的性能. 结果表明：在DGD分布方面，由DGD发生器构成的模拟器，一个DGD发生器就可与实际光纤PMD的统计特性相符合，而由保偏光纤和可旋转的连接器构成的模拟器则至少需要15段. 在自相关函数方面，基于保偏光纤的模拟器取决于各段光纤的延时量，而基于DGD发生器的模拟器在中心频带外的自相关值很平稳，可视为常数. 关键词： 光纤通信 偏振模色散 偏振模色散模拟器 自相关函数     

直接检测光OFDM系统中的偏振相关损耗研究

对于高速光传输,直接检测的光正交频分复用系统（direct detection optical orthogonal frequency division multiplexing, DDO-OFDM）中的偏振相关损耗（polarization dependent loss, PDL）与偏振模色散相互作用,对系统传输带来较大影响。对DDO-OFDM系统中PDL与一阶PMD作用机理和数学模型进行了分析,并通过数字仿真加以验证。结果表明:在PDL与PMD联合作用下,对OFDM信号幅度及相位均产生影响,通过发送导频序列可有效实现信号均衡;由于输出偏振态随频率产生旋转,PMD效应一定程度上缓解PDL所致系统损伤,差分群时延为50 ps条件下,以10 Gb/s的速率在单模光纤传输480 km,DDO-OFDM系统Q值提高约0.8 dB。     

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.     

Optical telecom networks as weak quantum measurements with postselection

We show that weak measurements with postselection, proposed in the context of the quantum theory of measurement, naturally appear in the everyday physics of fiber optics telecom networks through polarization-mode dispersion (PMD) and polarization-dependent losses (PDL). Specifically, the PMD leads to a time-resolved discrimination of polarization; the postselection is done in the most natural way: one postselects those photons that have not been lost because of the PDL. The quantum formalism is shown to simplify the calculation of optical networks in the telecom limit of weak PMD.     

一种可编程PMD模拟器

为了研究光纤通信中的偏振模色散(PMD)及其对高速光通信系统的影响和补偿技术,研制了一种可编程控制的PMD模拟器,它由6组双折射晶体和磁光晶体组成,群时延差(DGD)变化范围为±(0.3~35) ps,可设为不同平均值的Maxwell统计分布随机变化,也可以设为其它要求的数学分布.实验证明,该模拟器测量值与理论符合得很好,且具有较高的重复性和稳定性,响应时间小于1 ms.这种模拟器可用于10 Gb/s和40 Gb/s光传输系统PMD问题的研究.     

Tuneable polarization mode dispersion emulator: Fixed polarization maintaining fibre sections and rotatable polarization orientations

We design a polarization mode dispersion (PMD) emulator capable of adjusting first-order (FO-) and second-order (SO-) PMD statistics, making it capable to mimick differerent fibre links or fibre plants. The emulator can adjust PMD statistics by controlling mode coupling angles between polarization maintaining fibres (PMFs) of fixed length using its seven rotatable electro-optic polarization rotators which act as half waveplates (HWPs). The stability and repeatability of the emulator under a stable laboratory environment makes PMD statistics reproducible. The control mechanism of the emulator is in real-time.     

A deeper analysis of the second order polarization mode dispersion in optical communications systems

This article presents a new approach to the combined analysis of the first and second-order polarization mode dispersion (SOPMD) and shows their importance in optical communication systems performance. How it affects the relation between second-order polarization mode dispersion (PMD) and the differential group delay (DGD) in a single mode fiber is discussed. The analysis is based on time or wavelength and temperature variations changing/impacting PMD and DGD measured values. We present long term statistical characteristics of second-order PMD over a PMD emulator, and investigate the correlation between SOPMD, depolarization (DEP) and polarization dependent chromatic dispersion (PCD). Some authors calculate these modes from measurements obtained from the first order polarization mode dispersion, assuming a positive correlation between these effects, but this not the real relationship between them. A new interpretation of SOPMD was used to analyze the problem of the spectral stability in terms of the temperature. Actual techniques for determination SOPMD, consequently DEP and PCD, use the variation in time and/or wavelength. In some studies the results obtained for SOPMD are correlated to first-order PMD (FOPMD). This paper shows, based on measurements, that the correlation between first and second order Polarization Mode Dispersion (PMD) in the case where the last one is a function of the temperature can assume positive or negative values.     

Polarization effects and performance of fiber optic recirculating loops

Polarization effects such as PMD and PDL in a straight-line optical fiber communication system are random due to the random birefringence of optical fiber. However, since there is periodicity in a fiber recirculating loop, the polarization effects are quite different than in a straight line. Theoretically and experimentally we analyze the polarization effects in a loop and their effect on performance and the evolution of the state of polarization of a channel. Using this analysis, we are able to better understand the physical impact of the evolution of the state of polarization of a channel on performance. We show that loop-synchronous polarization scrambling is an effective way of breaking this periodicity in an attempt to make the recirculating loop perform more like a straight-line system.     

Combined effect of PMD and PDL on four-wave-mixing-induced crosstalk in WDM system

We derive an explicit autocorrelation function (ACF) formula of state of polarization for a fiber transmission system with polarization mode dispersion (PMD) and polarization dependent loss (PDL), which is found to agree well with Monte Carlo simulation. Then we use the new ACF to investigate the combined effect of PMD and PDL on the polarization multiplexed scheme. We find the performance of the polarization multiplexed scheme can be deteriorated more severely than the case without PDL.     

基于光信号偏振度的偏振模色散补偿系统的研究

偏振模色散已成为当前发展高速长距离光纤传输系统的主要限制因素。理论上分析了光纤一阶偏振膜色散效应对高速伪随机非归零码／归零码光信号偏振度的影响，并利用数值模拟的方法分析了信号不同输入偏振态以及高阶偏振膜色散效应对非归零码光信号偏振度的影响。最后对利用信号偏振度作为反馈控制信号的自适应偏振膜色散补偿系统的补偿性能进行了分析，大量统计分析结果表明对于10Gbit／s的非归零码光纤传输系统，当传输线路的平均偏振膜色散值小于43ps时，利用极大化输出信号偏振度的偏振膜色散补偿系统对信号眼图的补偿概率可以达到99．99％．     

PMD & PDL

We present the formalism required to describe the combined effects of polarization mode dispersion (PMD) and polarization dependent losses (PDL) in optical fibres. The combination of PMD and PDL may lead to anomalous dispersion, which is not correctly described by a direct application of the Jones Matrix Eigenanalysis (JME) method. An extended version of this work can be found in Huttner et al.     

The effect of variable PSP angles in a PMD compensator

A polarization mode dispersion compensator (PMDC) composed of two polarization mode dispersion (PMD) elements and one polarization dependent loss (PDL) element is proposed. Simulation shows that, due to the variable angle between the two principal states of polarization (PSPs) of the compensator, the proposed compensator can improve the PMD compensation efficiency for systems with both PMD and PDL, especially when higher order PMD is compensated.     

存在偏振相关损失条件下偏振模色散的特点

偏振模色散和偏振相关损失的联合作用，会产生不规则的色散现象，这一点不能直接通过琼斯距阵本征分析法的运用进行描述。由此引出了对偏振模色散和偏振相关损失共存条件下的研究。通过对琼斯本征分析法进行修正，来分析存在偏振相关损失条件下偏振模色散的特征距阵，理论分析表明，由于偏振相关损失的影响，即使在忽略差分损耗频率相关性的条件下，偏振模色散的特征距阵也会产生根本性的变化。     

偏振模色散矢量的研究

研究了无损光纤的密勒矩阵,进而得出了偏振模色散矢量的解析表达式、主偏振态对应的斯托克斯矢量的解析表达式,以及高阶偏振模色散矢量的解析表达式.这些解析表达式是由光纤参数决定的.讨论了局部偏振模色散矢量与整体偏振模色散矢量的关系,讨论了利用偏振模色散矢量进行偏振模色散补偿的原理.引入了偏振模色散补偿元件的偏振模色散补偿矢量C,具体计算了正规的非圆光波导类的补偿元件的C.从理论上证明了仅仅利用一个正规的非圆光波导类的补偿元件,例如一根保偏光纤或是一个双折射晶体,是不能实现偏振模色散补偿 关键词： 偏振模色散 密勒矩阵 色散补偿 主偏振态斯托克斯矢量     

PMD compensation using a fuzzy automatic polarization controller

A new first-order polarization mode dispersion (PMD) compensation technique is experimentally demonstrated in a 2.5 Gbit/s optical transmission system. It achieves adaptive compensation over a wide range of differential group delay (DGD) values, since it does not try to compensate it, but to eliminate one of the principal states of polarization by means of a liquid crystal polarization controller and a polarizer. The PMD parameters of the received signal are measured in real time through its spectrum analysis, and used as the feedback signal in a fuzzy logic algorithm controlling the liquid crystal device. The algorithm achieves a response time faster than the PMD variations in real links, also featuring endless operation. Moreover, a deterministic compact PMD emulator has been implemented in order to test the PMD compensator system.     

Compensating Large PMD by Four Free degrees in an OTDM System

In this paper, by introducing a two-stages polarization mode dispersion (PMD) compensator after a optical fiber link with a large PMD, we compensated over 270ps first-order and 2000ps2 high-order PMD in a optical fiber link with super high PMD. Our experimental results shows that, the compensators based on the two-stages of compensator can be used to PMD compensation in a 20Gb/s OTDM system with 60 km high PMD fiber. Before compensation,270ps DGD is became into max. 7ps after compensation. At simultaneity, the tunable FBG have a function of dispersion compensation.