40Gb／s光通信系统中光域偏振模色散补偿的实验研究

在40Gb/s归零码(RZ)大Polarization Mode Dispersion(PMD)光通信系统中，采用两级四自由度光域PMD(偏振模色散)补偿器，以信号的DOP(偏振度)为反馈信号，利用自适应优化算法，实现了一阶及高阶PMD动态自适应补偿．最大一阶PMD补偿能力为35ps，二阶PMD补偿能力为200ps^2，PMD动态自适应补偿器的优化补偿时间小于10ms．     

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。     

40Gb/s光通信系统中PMD补偿方案的分析与设计

对40Gb/s的高速光通信系统中的PMD补偿方案进行分析,给出了三种常用的补偿方案,从脉冲展宽角度指出不同的补偿方案会对传输距离有不同的限制.同时,指出了高阶PMD补偿的必要性.     

偏振模色散补偿的方法

文章指出偏振模色散(PMD)补偿的方法对高速光通信系统的危害,对现有的PMD补偿方案进行了综述,并比较了各种方案的优劣。指出保偏光纤(PMF)补偿PMD是目前比较可行的方法,但更有发展前途的补偿法应该是利用非线性光纤光栅。     

偏振模色散补偿的方法

文章指出偏振模色散（PMD）补偿的方法对高速光通信系统的危害。对现在的PMD补偿方案进行了综述，并比较了各种方案的优劣，指出保偏光纤（PMF）补偿PMD是目前比较可行的方法，但更有发展前途的补偿法应该是利用非线性光纤光栅。     

基于偏振度椭球的PMD补偿方法的研究

分析了PMD椭球的三个轴随PMD的变化规律,建立了以偏振度椭球的短轴作为PMD补偿的反馈信号的PMD补偿系统模型,并通过数值模拟对一阶和二阶PMD进行了补偿,结果表明采用这种方法能同时有效地补偿一阶及二阶PMD。     

基于偏振度椭球的PMD补偿方法的研究

分析了PMD椭球的三个轴随PMD的变化规律，建立了以偏振度椭球的短轴作为PMD补偿的反馈信号的PMD补偿系统模型，并通过数值模拟对一阶和二阶PMD进行了补偿，结果表明采用这种方法能同时有效地补偿一阶及二阶PMD。     

CSRZ-DPSK调制信号的PMD补偿性能分析

主要研究新型调制格式CSRZ-DPSK的PMD补偿性能,从理论上推导了CSRZ-DPSK信号的调制原理公式,并给出了实现的具体过程,通过Matlab仿真得到了NRZ、CSRZ、NRZ-DPSK和CSRZ-DPSK的调制信号经过PMD补偿系统前后的DOP值.结果表明,与00K格式相比,DPSK调制格式补偿后的DOP值更多的分布在接近1的范围,其中CSRZ-DPSK具有最好的PMD补偿效果,是实现PMD补偿的首选格式.     

WDM光纤通信系统中PMD自动补偿的研究

文章提出采用粒子群优化算法,提取信号的偏振度(DOP)作为反馈信号来补偿多信道光纤通信系统中的偏振模色散(PMD).作为例子,对两信道的波分复用(WDM)系统中的PMD进行了自动补偿,并进行了数值模拟,得到了两个信道补偿前后的DOP以及眼图变化情况.模拟结果表明这种算法对补偿多个信道的PMD是有效的.     

偏振模色散的光域补偿方法研究

针对光纤传输中的偏振模色散(PMD)问题,研究和比较了现有PMD的光域补偿方法.利用等效啁啾技术,提出了一种基于啁啾光纤光栅的光域补偿方案,用具有光敏性质的保偏光纤制成啁啾光纤光栅,将其作为PMD补偿器中的时延线,实现了PMD的自适应反馈补偿.实验结果显示,该方案能有效补偿光纤传输中的PMD问题,提高光信号的传输质量.     

高速光纤通信系统中高阶PMD补偿技术研究

随着光放大器和色度色散补偿技术的不断提高，光纤的偏振模色散（PMD）已经成为超高速、超长距离光纤通信系统发展的主要障碍，在40Gbit/s或更高速率的光纤通信系统中，PMD的影响已不可忽略，必须考虑PMD的补偿问题，从高阶PMD对40Gbit/s NRZ系统影响的数值模拟发现，当光纤中PMD高阶效应比较明显时，将严重劣化一阶PMD补偿的效果，另外，通过对两种高阶PMD补偿器的比较介绍，认为两段级联的高队PMD补偿系统是一种比较现实的补偿方法。     

偏振模色散及其补偿

偏振模色散（PMD）是限制超高速光传输系统发展与应用的重要因素，文章分析了PMD对光传输系统速率和传输距离的限制，讨论了消除其影响的补偿方法。     

偏振模色散补偿系统中自适应反馈控制技术的研究

偏振模色散（PMD）已成为发展下一代高速长距离光纤传输系统的主要制约因素，本文中分析了分析了PMD补偿系统中几种自适应反馈控制技术，并详细比较，讨论了各自的特点，认为偏振度测量法是一种首选技术。     

MLSE Equalizers for Frequency Discrimination Receiver of MSK Optical Transmission System

We propose maximum-likelihood sequence estimator (MLSE) equalizers based on either Viterbi algorithm or template matching temple matching (TM) for the equalization of impairments imposed on the minimum shift keying (MSK) modulation formats in long haul transmission without optical dispersion compensation. The TM-MLSE equalizer is proposed as a simplified alternative for the Viterbi-MLSE equalizer. It is verified that the Viterbi-MLSE equalizer can operate optimally when noise approaches a Gaussian distribution. Simulation results of the performances of the two MLSE equalizers for optical frequency discrimination receiver-based optical MSK systems are described. The transmission performance is evaluated in terms of: (1) the chromatic dispersion (CD) tolerance for both Viterbi-MLSE and TM-MLSE equalizers; (2) transmission distance limits of Viterbi-MLSE equalizers with various number of states; (3)the robustness to fiber polarization mode dispersion (PMD) of Viterbi-MLSE equalizers; and (4) performance improvements for Viterbi-MLSE equalizers when utilizing sampling schemes with two and four samples per bit over the conventional single sample per bit. With a small number of states (64 states), the non-compensating optical link can equivalently reach up to approximately 928 km SSMF for 10 Gb/s transmission or 58 km SSMF for 40 Gb/s. The performance of 16-state Viterbi-MLSE equalizers for optical frequency discrimination receiver (OFDR)-based optical MSK transmission systems for PMD mitigation is also numerically investigated. The performance of Viterbi-MLSE equalizers can be further improved by using the sampling schemes with multiple samples per bit compared to the conventional single sample bit. The equalizer also offers high robustness to fiber PMD impairment.     

Effect of PDL on the DOP feedback signal in PMD compensation

The impact of polarization dependence loss (PDL) on the degree of polarization (DOP) feedback signal in polarization mode dispersion (PMD) compensation is analyzed. PDL affects DOP only in the presence of PMD, and in the presence of PMD and PDL, DOP relates not only to both PMD and PDL vectors but also to the principal states of polarization (SOPs) components of the output signal; on the other hand, it adds new frequency dependence and is no longer independent of system bit rate. The PDL minimum endangering PMD compensation is determined by the step size of the PMD compensating algorithm and the differential group delay (DGD) value in optical fiber systems. DOP could no longer act as the feedback signal in PMD compensation unless the PDL in the fiber system has been effectively eliminated before PMD compensation.     

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。     

高速光纤通信中的偏振模色散及其补偿技术

偏振模色散已成为当前发展下一代高速长距离光纤传输系统的主要限制因素,介绍了偏振模色散的概念、描述方法以及测试和补偿技术。根据国外的研究情况和我国的具体实情,指出研究振模色散的测试和补偿技术对提高我国高速光纤通信技术的水平具有重大意义。最后在此基础上提出了开展相关研究的建议。     

高速传输系统的偏振模色散补偿技术

随着光网络的快速发展,系统的传输码率逐渐提升,传输技术也不断地发展和完善。光纤传输系统中的各种因素造成的影响程度也出现了很大的变化。针对偏振模色散(PMD)对高速光纤传输系统造成的损害,对目前光域和电域的PMD补偿技术进行详细的阐述。通过比较各种方案,指出高速光纤传输系统中PMD的光域补偿技术更适用,发展空间大,而且性能好。其中光纤光栅补偿技术应用广泛,对单信道和多信道传输系统都适用。因此,光纤光栅技术最具发展潜力。     

Analysis of signal degree of polarization degradation used ascontrol signal for optical polarization mode dispersioncompensation

The basic property of degree of polarization (DOP) degradation of optical signal induced by polarization mode dispersion (PMD) in high-speed optical fiber transmission is investigated in detail. The DOP of the optical signal reflects the degree of waveform degradation caused by PMD, therefore, it is proposed to be used as the control signal judging the best compensation point for the optical adaptive PMD compensation techniques. However, the signal DOP is not only affected by PMD, but also by various factors, such as the modulation format, modulator chirp, fiber nonlinearity, amplified spontaneous emission (ASE), and so on. We use numerical simulations and experiments to explore the basic DOP property to detect PMD with these factors. We also show that using the signal DOP as control signal is especially useful for the optical duo-binary modulation because of its high sensitivity and wide PMD detection range     

Performance of turbo equalizers for optical PMD channels

This paper investigates the performance of iterative (turbo) equalization to mitigate the effects of a polarization-mode dispersion (PMD) in nonreturn-to-zero (NRZ) intensity-modulated optical-fiber transmission systems. A PMD can lead to severe distortions in the received electrical signal and is a key limiter for the development of high-bit-rate transmission over currently used fibers. In order to reduce the distortions due to a PMD, the performance of symbol-by-symbol maximum a posteriori (sbs-MAP) soft-in/soft-out (SISO) decoders is studied. The SISO algorithms are adapted to the noise statistics of the optical channel where the photo detector leads to a non-Gaussian signal-dependent noise at the receiver side. The modified SISO algorithms are successfully employed for turbo equalization and results show that iterative (turbo) equalization and decoding for the compensation of a PMD can lead to a tremendous reduction in the bit error ratio (BER). Moreover, it is shown that, due to the robustness of mutual information, the extrinsic information transfer (EXIT) chart can be applied for the design of iterative receivers in optical transmission systems even with a non-Gaussian noise.