光通信系统中偏振模色散克服技术

由于光通信系统的速率不断提升 ,克服偏振模色散已成为高速光通信系统中急需解决的问题。现仅对国内外现有的偏振模色散克服技术作一回顾和分析     

高速光通信系统中偏振模色散的补偿

光纤中偏振模色散已成为高速光通信系统增容的主要障碍,文章对现有的各种偏振模色散补偿方法进行了综合评述。认为用偏振控制器与保偏光纤构成的夺模色散自动补偿系统是一种首选方案。     

高速光纤通信系统中高阶偏振模色散的抑制措施

光纤通信线路的偏振模色散已成为高速、长距离光纤通信系统发展的主要障碍之一。目前大量的研究集中在对一阶偏振模的研究，本文分析了高阶偏振模色散的抑制原理和抑制方案。     

Density-matrix-formalism based scheme for polarization mode dispersion monitoring and compensation in optical fiber communication systems

We propose a density-matrix-formalism based scheme to study polarization mode dispersion (PMD) monitoring and compensation in optical fiber communication systems. Compared to traditional monitoring and compensation schemes based on the PMD vector in the Stokes space, the scheme we proposed requires no auxiliary matrices and can be handily extended to any higher-dimensional modal space, which is advantageous in mode-division multiplexing (MDM) systems. A 28 GBaud polarization division multiplexing quadrature phase-shift keying (PDM-QPSK) coherent simulation system is built to demonstrate that our scheme can implement the monitoring and compensation of 170 ps large differential-group-delay (DGD) that far exceeds the typical DGDs in practical optical communication systems. The results verify the effectiveness of the density-matrix-formalism based scheme in PMD monitoring and compensation, thus pave the way for further applications of the scheme in more general MDM optical communication systems.     

Chromatic dispersion allocable compensator for optical fibre communications systems

In this work we perform a study about the temperature implications on the optical fibers chromatic dispersion and the implications on the quality of transported information. To solve this constrain we suggest two approaches to dynamically compensate chromatic dispersion, one based on chirped fiber Bragg gratings and other based on dispersion compensation fibers. With the dispersion compensation fibers, we obtain a first and second order tuning coefficients of 3.472 ps nm-1 ºC-1 and -2.7 × 10 -3 ps nm-2 ºC-1, respectively. With the compensator based on chirped fiber Bragg gratings we obtain dispersion values between -113.2 ps nm-1 and 143.1 ps nm-1, for temperature gradients of 40ºC.     

Time evolution of polarization mode dispersion in optical fibers

The fluctuation of polarization mode dispersion (PMD) due to environmental change is an important issue for fiber-optic communication systems. We measure the time evolution of PMD for installed aerial and buried cables and for a spooled fiber in a temperature controlled chamber. The results show that PMD fluctuates much more rapidly for aerial cables than for buried cables. The magnitude of PMD is different for the three fibers and our results also show that the magnitude of PMD fluctuation depends on the magnitude of the PMD     

偏振模色散仿真器特性研究

光纤通信线路的偏振模色散已成为高速、长距离光纤通信系统发展的主要障碍之一 ,其特性、测量以及补偿方法的研究成为目前光纤通信研究热点之一。偏振模色散仿真器 ,用于仿真传输链路的偏振模色散特性 ,不仅可用于偏振模色散补偿器 ,也可用于高速长距离光纤通信系统的规划设计等。本文分析了光纤偏振模色散仿真器的研究现状 ,归纳总结了现有偏振模色散仿真器的设计原理和结构特征 ,并用蒙特卡罗法对常用的偏振模色散仿真器的特性进行了数值模拟     

海底系统的偏振模色散研究

由于海底应用环境复杂,海底光缆会受到海水的压力、冲击和暗流等作用,具有随机性的偏振模色散(PMD)成为系统极限传输的限制因素.文章对横向应力、弯曲等外界因素对PMD的影响进行了理论分析,根据海底光缆的实际工作情况,模拟4×2.5 Gbit/s系统取3 dB的功率冗余度,进行了PMD仿真,得出系统正常工作时PMD系数不超过1.8 ps/km的结论.为避免PMD补偿,当弯曲半径为0.3 m时,要求横向应力不得大于8.9 N/m.     

Measurement of polarization mode dispersion in systems having polarization dependent loss or gain

The principal states of polarization and their propagation characteristics are analyzed for both unitary and nonunitary optical systems in terms of the complex plane representation of polarization. A new method for the estimation of the polarization mode dispersion of the system is proposed together with experimental and simulation results.     

Statistical characteristics and effects of polarization mode dispersion in dispersion managed soliton systems

Recently,the dispersion-managed solitons(DMS) areof great interest in soliton communication systems .Be-cause of some prior advantages compared with conven-tional solitons ,such as higher pulse energy and signalnoise ratio,lower averaged dispersionline an…     

Three-stage polarization mode dispersion compensator capable of compensating second-order polarization mode dispersion

The impacts of polarization-dependent dispersion on systems are investigated briefly, based on which a three-stage polarization mode dispersion compensator has been proposed to compensate polarization-dependent chromatic dispersion and the principal states of polarization rotation rate at the same time. The two possible operating points of this compensator are also proposed. Numerical results show that the maximum tolerable polarization mode dispersion value after three-stage compensation has been improved by 17% per bit slot compared with using a two-stage compensator.     

偏振模色散及其补偿技术

当前,偏振模色散(PolarizationModeDispersion,PMD)已经成为限制高速光通信技术发展的主要因素。介绍了PMD产生的原因,对目前常有的PMD补偿技术进行了分析、评价,重点分析了其中的光补偿技术。     

基于光环形器的光传送网通信偏振模色散抑制

为了降低光传送网传输过程中产生的偏振模色散对传输信号质量的影响,采用将光环形器置于光传送网光放大器前端的方法,对光传送网通信传输中的偏振模色散效果进行了仿真。经过偏振模色散抑制后,传输眼图具有更加明显的张开状态,系统的传输性能有一定的提高,在一定程度上抑制了光传送网中存在的偏振模色散,有效改善了信号的质量。结果表明,从添加光环形器前后补偿偏振模色散的误比特率计算结果发现,误比特率的效率提高了约1倍,光环形器对光传送网通信的偏振模色散现象具有显著的抑制效果。该方案对不同传输速度的偏振态光信号延迟进行等效补偿,最终实现补偿偏振模色散的效果。     

一种高速光纤通信高阶偏振模色散补偿的前馈信号提取方法

建立了一种实时提取一阶和二阶偏振模色散的模型,可以直接得到偏振模色散的大小和方向。通过数值模拟将得到的偏振模色散大小与从琼斯矩阵理论中计算的结果进行比较,我们模拟结果与理论计算值在差分群时延为一个比特周期内较好相符。从得到的偏振模色散矢量的大小和方向信息可以为高阶阶偏振模色散补偿提供前馈信息     

Effect of cabling on polarization mode dispersion in optical fiber ribbon cables

This paper theoretically and experimentally investigates an effect of cabling on polarization mode dispersion (PMD) in ribbon fibers helically stranded in optical fiber ribbon cables aimed at designing low PMD ribbon cables. Based on the birefringence model focused on the change in the birefringence when ribbon fibers are cabled, the helical pitch of optical fiber ribbon cables is designed to minimize the maximum PMD in the cables. A low PMD characteristic is confirmed in optical fiber ribbon cable with approximately the optimal helical pitch.     

Effect of map strength on polarization mode dispersion in dispersion-managed soliton systems

Solitons in dispersion managed lines have large tolerance to polarization mode dispersion (PMD) because of the strong nonlinear trap helped by a power enhancement factor compared with conventional solitons. We present numerical results on the effect of map strength S on PMD and discuss the optimum choice of S in practical soliton systems.     

Effect of polarization mode dispersion on a coherent optical systemwith pilot carrier

The effect of fiber polarization mode dispersion (PMD) on a coherent optical system with pilot carrier is twofold. First, the PMD causes state of polarization (SOP) mismatch between the message signal and the pilot carrier. Second, the degrees of polarization (DOPs) of the message signal and pilot carrier are degraded by PMD. Because coherent reception relies both on the SOPs and DOPs of the waves, system performance is degraded by PMD. The effect of SOP mismatch causes intermediate frequency (IF) signal amplitude degradation, whereas DOP variation not only results in IF signal amplitude degradation but further induces IF noises. Analytical expressions are derived to evaluate the performance degradation. It is shown that there is no performance degradation if only one principle state of polarization is excited and maximum degradation occurs when both principle states of polarization are equally excited. It is found that significant degradation may happen when large differential group delay exists     

Some enabling techniques for polarization mode dispersion compensation

Progress toward 40-Gb/s polarization-mode dispersion (PMD) compensation is presented in several areas. A single-waveplate polarization scrambler that generates Stokes' parameters with just three harmonics has been realized. Together with an arrival-time detection scheme, it allows the detection of about 1 ps of PMD within 2.4 /spl mu/s in a 40-Gb/s nonreturn-to-zero transmission setup. A scrambler that operates independent of its input polarization has also been realized. Both scramblers can be shared among a number of wavelength-division-multiplexed (WDM) channels for which PMD is to be detected. Furthermore, an inverse scattering technique has been implemented to determine differential group-delay profiles of an improved distributed PMD compensator in X-cut, Y-propagation LiNbO/sub 3/. In this context, the most common kind of higher order PMD is identified, which typically persists after compensation of first-order PMD. In a fiber link with polarization scrambling, it is shown to be measurable in a most efficient manner by comparing the rising and falling slopes of the detected signal using two oppositely poled one-way rectifiers placed at the output of a differentiator.     

A dynamical polarization mode dispersion emulator

A polarization mode dispersion (PMD) emulator is presented which accurately follows the dynamics of PMD in field optical fiber. A modification on a dynamic mode coupling wave-plate model is presented to model the emulator. It is found that the emulator and model can accurately describe the dynamical behavior of the state of polarization and thus PMD in a field fiber. The emulator is shown to be repeatable. Generally, the dynamical PMD emulator is shown to cause more realistic bit-error-rate degradation than a classical PMD emulator.     

Comparison of polarization mode dispersion emulators

We analyze polarization mode dispersion (PMD) emulators comprised of a small number of sections of polarization-maintaining fibers with polarization scattering at the beginning of each section. Unlike previously studied devices, these emulators allow the emulation of a whole ensemble of fibers. We derive an analytical expressions and determine two main criteria that characterize the quality of PMD emulation. The experimental results are in good agreement with the theoretical predictions