Statistical description of optical system performances due torandom coupling on the principal states of polarization

Due to polarization-mode dispersion (PMD), the performances of an optical transmission system show a random behavior. We calculate the probability density function of the Q-factor due to PMD. We adopt the principal states of polarization model, and we also consider the clock recovery behavior at the receiver. Theoretical results are reported for a 40-Gb/s system, and are compared with those obtained considering the effect of pulse broadening due to PMD     

InP-based 10-GHz bandwidth polarization diversity heterodynephotoreceiver with electrooptical adjustability

A polarization diversity optical receiver, integrated with two pairs of balanced photodiodes in the InP/InGaAsP material system, is described. This circuit includes two polarization splitters based on modal birefringence and, for the first time, adjustable 3-dB TE and TM directional couplers (relaxing fabrication tolerances). On-chip losses are below 2.5 dB (TE) and 5.5 dB (TM). Waveguide to PIN coupling efficiency is >95%. Polarization crosstalk is in the 9-10-dB range, 3-dB couplers balance can be recovered, and common mode rejection ratio (CMRR) lower than -30 dB is obtained and remains below -20 dB over 6 GHz. Balanced receiver circuit 3-dB bandwidth is in excess of 10 GHz     

Direct bandwidth and polarization control of an XeF unstableresonator laser

Several approaches to directly controlling the bandwidth and polarization of an unstable resonator without the use of an injection source are discussed. The techniques are based on the control of oscillations within (and around) the resonator core through the use of small, subaperture optical elements (e.g. etalons, Brewster-angle plates, Glan-air prisms) mounted at select locations within the system. The experiments were performed on a 4-J, e-beam pumped, XeF ( B→X) laser operating at ambient temperature, with output predominantly at 353.2 nm. A spectral linewidth of less than 12 GHz (0.05 Å) and nearly perfect linear polarization were simultaneously achieved at high laser efficiency. Oscillation on a single, dominant transverse mode has been demonstrated. The increased cost and complexity of injection-controlled systems are avoided through the use of these direct, core-control approaches     

单模光纤中椭圆双折射下偏振模色散特性研究

为了分析椭圆双折射对偏振模色散的影响,将模型中的偏振模色散(PMD)矢量及极化相关损耗(PDL)矢量设定为椭圆偏振矢量,应用保偏光纤(PMF)级联模型和蒙特卡罗仿真方法,研究在PDL影响下的PMD统计特性。研究表明,PMD和PDL矢量的椭圆偏振程度对PMD的统计分布和均值大小均会有影响;在椭圆偏振和PDL的联合影响下,PMD的统计分布为Maxwell和Gaussian分布的合分布。研究结果对偏振模色散的测试、补偿和系统设计均具有参考价值。     

Adaptive polarization transmission of OFDM signals in channels with polarization mode dispersion and polarization-dependent loss

A 2x2 multiple-input multiple-output (MIMO) architecture using dual-polarized antennas (DPAs) is considered with orthogonal frequency division multiplexing (OFDM). The performance of DPAs is evaluated for adaptive polarization (AP) transmission techniques in time-varying multipath channels impaired by polarization mode dispersion (PMD) and polarization-dependent loss (PDL). AP transmission techniques considered include power gain maximization, polarization dispersion minimization for interference avoidance, polarization multiplexing with waterfilling, and a suboptimal multiplexing strategy that enables direct recovery of the polarization multiplexed streams, thereby simplifying the design of the receiver. Measured time-varying dual-polarized channel realizations from mobile-to-mobile experiments are used to estimate the capacity, diversity, and interference avoidance performance of the adaptive approaches.     

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     

Tracking and separation of time-varying principal states of polarization in optical fiber link for first-order PMD compensation and its filter-dependent performance

We propose a simple method for tracking and separating time-varying principal states of polarization (PSP) occurring in a fiber-optic transmission link with polarization mode dispersion (PMD) for use in PMD compensation. The proposed method uses as a feedback monitoring signal the bandpass-filtered RF power at bit-rate frequency for NRZ signal format. We demonstrated the operating principle of the method through theoretical simulation and experiment using an automatically adaptive PMD compensator employing a single polarization beam splitter (PBS). The effects of electrical filtering on the PSP tracking performance were also investigated by using three types of filters, i.e., a low-pass filter (LPF), a band-pass filter (BPF), and a high-pass filter (HPF). The simulation results showed that only a BPF centered at bit-rate frequency was found to allow for tracing and separation of two PSPs via PBS. The proposed method, when applied to a conventional PMD compensator that alternately controls a polarization controller and a delay line, enables separation of PSP control from differential-group-delay (DGD) control, thus allowing fast tracking of rapidly changing PSP in a PMD-impaired optical fiber link and reducing compensation time.     

Use of principal mode numbers in the theory of microbending

The modal theories of microbending that have been proposed so far postulate that modes that have the same principal mode number carry the same optical power. This assumption is shown to be incorrect. The exact result is given.     

Dynamic bandwidth control of the virtual path in an asynchronoustransfer mode network

The virtual path concept has several valuable features to construct an economical and efficient asynchronous transfer mode (ATM) network. One of them is bandwidth control which affords transmission efficiency improvement through statistical sharing of capacity. An effective bandwidth control algorithm and its calculated performance are described. Network performance with the algorithm is evaluated, and the bandwidth control is shown to successfully improve network transmission efficiency with only a slight increase in processing load compared to the fixed bandwidth scheme. A method is also proposed to equalize call loss probability for each virtual path. The effectiveness of the method is demonstrated by analysis     

标度放大和自适应同步识别约瑟夫森结混沌系统中非同阶参数

约瑟夫森结是一个很重要的超导元件,其电路模型关键参数的数值差别很大,传统的自适应同步方法不能准确识别小幅度参数。基于李亚谱诺夫稳定性理论构造带有增益系数的控制器和参数观测器, 结合标度放大方法对约瑟夫森结混沌系统不同阶参数进行识别。以误差函数为统计量,在增益系数和放大因子的相空间给出同步和非同步区域分布,发现对两个小参数同时进行标度放大可以增加同步区域。该方法可以显著提高小参数的识别精度, 数值计算结果验证了该方法的有效性。     

Autocorrelation function of the principal State of polarization vector for systems having PMD

The autocorrelation function (ACF) for the principal state of polarization (PSP) vector is reported. It is shown that the PSP vector ACF and the magnitude of the polarization-mode dispersion vector, i.e., the differential group delay (DGD) ACF are not independent. The PSP vector correlation bandwidth is verified to be narrower than that of the DGD.     

光子晶体缺陷模的偏振特性研究

为了了解光波在一维光子晶体的传输特性,利用传输矩阵方法进行了数值模拟,并研究了缺陷层厚度对缺陷模偏振特性的影响.结果表明,入射角的变化对光子晶体的禁带及缺陷模影响较大,它们都随入射角的增大向高频(短波)方向移动,s偏振的禁带宽度逐渐增宽而p偏振的禁带宽度变化不明显,p偏振的缺陷模频移较s偏振的稍大.随着入射角的增大,s偏振的缺陷模越来越细、品质因子逐渐增大,而p偏振的缺陷模变化趋势则刚好相反.     

用偏振模色散模拟器加偏振片实现带内光信噪比检测

提出了一种基于偏振模色散(PMD)模 拟器加偏振片的带内检测光信噪比(OSNR)的方法,理论分析了检测方 法的工作原理,证明了方法不受光纤链路色散和PMD的影响,并且与信号偏振态 、调制格式及传输 速率无关。测试结果表明:在9dB到34dB的测量范围 内,本文检测方 法的测量误差在0.5dB内;在1dB的测量误差范围内,对偏振相关损 耗(PDL)的容忍范围为1dB。     

Mean-square performance of the family of adaptive filters with selective partial updates

In this paper we present a general formalism for the family of adaptive filter algorithms with selective partial updates. Based on this, the mean-square performance analysis of this family of adaptive filters is presented in a unified way. This analysis is based on energy conservation arguments and does not need to assume a Gaussian or white distribution for the regressors. We demonstrate through simulations that the results are useful in predicting the performance of this family of adaptive filters.     

Statistical treatment of the evolution of the principal states ofpolarization in single-mode fibers

A simple relationship is found for the evolution of the principal states of polarization (PSPs) and their differential group delay in fiber links. A simple expression is found, using the relationship, for the probability of the differential group delay (DGD), considering the evolution of the PSPs as a Brownian motion. The theory has been verified experimentally on an optical cable composed of 12 single-mode, shifted-dispersion fibers 2.2-km long. The results show that the DGD grows as the square root of the length when the length of the fiber is far larger than the correlation length of the perturbation. The measured value of DGD can vary substantially in two fibers belonging to the same ensemble, and in the same fiber, considering two frequencies differing by more than 5 nm     

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     

四态偏振编码解码QKD系统的实验研究

采用一个激光器通过偏振调制器快速偏振编码实现密钥分配,同时用矩阵分析的方法对系统原理进行了理论分析.指出用相位-偏振调制器可以对四种非正交偏振态光子进行编码和解码.在实验室内完成了30 km光纤保密通信,误码率<6%.实验表明该系统可用一个激光器快速编码解码实现密钥分配,具有很高的实用价值.     

偏振模色散监测技术的研究进展

文章对动态PMD(偏振模色散)监测技术的原理进行了阐述,分别对基于RF(射频)信号的监测技术、基于信号DOP(偏振度)的监测技术和基于非线性效应的监测技术等动态PMD监测技术的系统结构和性能指标进行了分析和比较,指出了这些技术的核心原理及存在的问题,并探讨了未来高速动态全光网络中PMD监测技术的发展趋势.     

随机电磁光束在生物组织中偏振态的变化

基于广义惠更斯-菲涅尔原理,以随机电磁高斯- 谢尔模型(GSM)光束作为典型的随机电磁光束,推导了随机电磁GSM 光束在生物组织中交 叉谱密度矩 阵元的解析表达式,并用以研究了其在生物组织中传输时轴上偏振度、方位角和 椭圆率的变化。结果表明,随机电磁GSM光束在生物组织中轴上偏振度、方位 角和椭圆率的变化与折射率结构常数C²_n、光束参数(λ,σ_yy和 σ_xy)及传输距离z有关; C²_n越大,轴上偏振度P极值越小,轴上方位角θ和轴上椭圆率ε极值越大, 且极值对应的传输距离越小;当σ_xx固定,σ_xx与σ_yy差值的绝对值越 大,P、θ和 ε随传输距离的变化率越大;σ_xy越大,P、θ和ε极值越大;光束在生物组织中 传输时,光的偏振态随传输距离的变化范围是很浅的。