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.     

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.     

能够补偿二阶偏振模色散的三阶段偏振模色散补偿器

简要分析了偏振相关色散对光通信系统性能的影响,提出了一种三阶段高阶偏振模色散补偿方案,从理论上分析了它同时补偿偏振相关色散和偏振主态旋转的可能性,并提出了其可能存在的两种工作方式.通过数值模拟与两阶段补偿方案进行了性能比较,其偏振模色散容限比两阶段补偿提高约17%个比特周期 关键词： 光通信 光偏振 光纤色散     

A novel adjustable PMD compensator based on a tapered high-birefringence linearly chirped fiber Bragg grating

A novel solution for polarization mode dispersion (PMD) compensation is proposed by applying tension on a tapered high-birefringence linearly chirped fiber Bragg grating. The compensated differential group delay changes with the applied tension, for its cross-sectional area varies nonlinearly along the grating. Its performance as PMD compensator for short pulses fiber-optical transmission system and 10 Gb/s NRZ fiber-optical transmission system is demonstrated experimentally.     

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。     

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.     

Impacts of polarization mode dispersion on the pulse-width with considering initial pulse chirp and fiber GVD

The impacts of polarization mode dispersion (PMD) on the pulse-width in linear systems have been investigated. The analytical solutions, including the effects of initial frequency chirp and group velocity dispersion (GVD), are derived. Analyses show that the pulse broadening effects induced by the second-order PMD depend on GVD and chirp parameter, which are different from those induced by the first-order PMD. An initially chirped Gaussian pulse is taken as an example, upon which analytical solutions of rms pulse-width are derived before and after the first-order PMD compensation. The first-order PMD compensator is also evaluated based on these solutions. The results show that the pulse broadening effects will be resisted efficiently by choosing appropriate GVD and chirp parameter; in general, the post-transmission compensation method will be less efficient than the PSP-transmission method.     

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.     

An experiment of PMD compensation in 40-Gb/s PSBT transmission system

An adaptive polarization mode dispersion （PMD） compensation experiment is reported in a 40-Gb/s phase shaped binary transmission （PSBT） communication system, with the use of a new digital signal processor （DSP）-based optical PMD compensator. PMD tolerance is found to be enhanced by 8 ps after PMD compensation with 1-dB optical signal-to-noise ratio （OSNR） penalty. Under the condition of fast change of states of polarization up to 85 rad/s in the fiber link, the performance of our PMD compensator undergoes the bit error ratio （BER） test for as long as 10 h.     

Polarization mode dispersion and chromatic dispersion compensation by using a three-stage compensator

A three-stage compensator used for Polarization mode dispersion (PMD) and Chromatic dispersion (CD) compensation is proposed. The compensator is capable of compensating the two components of second-order PMD when no CD exists. Two operating points of compensating second-order PMD have been proposed. Two-stage and three-stage compensators are compared by the outage probability. When CD is introduced, the compensator should retain a quantity of second-order PMD to compensate CD. The outage probability when PMD and CD coexist has been calculated. The results show that a tradeoff must be made in order to compensate CD and PMD at the same time.     

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.     

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。     

4×10Gb/s OTDM系统中偏振模色散自适应补偿的研究

利用信号偏振度为反馈信号，基于可变步长最大值搜索算法实现了4×10?Gb/s 光时分复用 （OTDM）系统偏振模色散（PMD）自适应跟踪补偿实验.PMD补偿器为偏振控制器加可变时延 线的四自由度结构.最大差分群时延（DGD）补偿量为25?ps，即信号的一个比特周期，补偿 时间小于50?ms. 关键词： 偏振模色散 光时分复用系统 偏振度 自适应补偿     

Two-stage adaptive PMD compensation experiment for 10-Gb/s optical communication system

We report the adaptive compensation experiment of polarization mode dispersion (PMD) for 10-Gb/s non return-to-zero (NRZ) and return-to-zero (RZ) optical communication systems using a two-stage PMD compensator and the monitoring technique based on degree of polarization (DOP) feedback-signals. The DOP monitor has its advantages of bit-rate independent and modulation format independent. The two-stage compensator has the capacity of compensation for the first- and second-order PMD. The compensated differential group delay (DGD) is up to 80 ps, and compensated principal state of polarization rotation rate is 20 ps. The time used for compensation is less than 1 second.     

Jones precoder for polarization mode dispersion compensation

A new electrical-domain precoder is proposed to mitigate polarization mode dispersion (PMD) in optical communications by modeling a PMD-dominant fiber optical channel using a single input multiple output (SIMO) channel. Employing a bank of finite impulse response filters and a polarization modulator, and using parameters derived from the Jones matrix representation of PMD, the proposed precoder efficiently adapts to the time-varying nature of PMD and simultaneously pre-equalizes both polarization modes at the transmitter. The transmitter-only structure avoids losing phase and polarization information due to the nonlinearity of the commonly used square law direct-detection receiver. Analysis is performed to evaluate the impact of channel mismatch due to feedback delay, channel estimation errors, and the impact of the finite length of the precoder filters. The analytical results are used to guide selection of the appropriate feedback rate for the adaptive system. Extensive simulation results confirm the efficiency of the proposed Jones precoder, and present it as an effective, low-cost replacement to the complicated, expensive optical-domain counter-parts.     

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.     

A novel tunable polarization mode dispersion compensator with strain chirped fiber Bragg gratings

A tunable polarization mode dispersion (PMD) compensator based on strain-chirped fiber Bragg gratings (FBGs) is proposed. It natures in flexible designing, large tuning range, without using linear or nonlinear chirped phase mask, fast tuning response time, continuously adjustable, all-fiber based, compact, and cheap.     

Dynamic PMD compensation in 40-Gb/s optical communication system

A 40-Gb/s optical time division multiplexing (OTDM) return-to-zero (RZ) transmission experiments in cluding a dynamic polarization mode dispersion (PMD) compensation was reported. The dynamic PMD compensator is made up of two-stage four degrees of freedom (DOF). The first stage adopts polarization controller and fixed time-delayed line. The second stage is variable differential group delay (DGD) element. The PMD monitoring technique is based on degree of polarization (DOP) as error signal. A novel practical adaptive optimization algorithm was introduced in dynamic adaptive PMD compensation. The experimental results show that the performance of the PMD compensator is excellent for 40-Gb/s RZ transmission systems with the large DGD. With this compensator, a significant improvement of system performance can be achieved in the eye pattern of a received signal. The first-order compensating ability of the compensator is greater than 30 ps. The second-order compensating ability is greater than 200 ps2.The first-order optimum compensating time is within 10 ms. The second-order optimum compensating time is within 24 ms.     

Pulse broadening due to polarization mode dispersion with first-order compensation

We give the exact analytical expression for the autocorrelation function of the polarization mode dispersion (PMD) vector of a fiber link in which first-order PMD is compensated for at the output. We use the result to obtain the mean-square width of a Gaussian pulse in the presence of a first-order PMD compensator.