DPSK色散管理孤子传输系统性能分析

采用变分法研究基于差分相移键控（DPSK）色散管理孤子（DMS）系统中的放大器的自发辐射（ASE）噪声与交叉相位调制（XPM）对孤子传输特性的影响，从降低ASE噪声和XPM扰动引起的均方相位抖动出发，给出了3种传输管理方案。确定了特性参数色散管理强度S优选范围为1．5～3．0；以ASE噪声扰动为主的单信道系统中，前后对称补偿方案最好；以XPM扰动为主的波分复用（WDM）系统中，以不对称的后补偿方案最优。     

色散控制WDM孤子通信系统中的定时抖动

采用拉格朗日变分法在同时考虑本信道放大自发辐射 (ASE)噪声、相邻信道信号对本信道信号和ASE噪声等多种因素影响的情况下 ,分析了色散控制孤子的传输演化特性 ,给出了准稳态色散控制孤子传输动力学方程和定时抖动解析表达 ,并给出了三种扰动因素影响程度的比较。     

普通单模光纤中光孤子传输问题的研究

在使用普通单模光纤的光孤子传输系统中,放大器自发辐射（ASE）噪声和色散波逸出是限制光孤子传输的两个主要因素,它们将引起孤子能量科动和定时抖动,从而导致系统误码。本文分别研究了带限光滤波器对ASE噪声的抑制和非线性增益对色散波的抑制以及对孤子传输系统的稳定作用,并设计了使用普通单模光纤的光孤子传输系统。     

WDM系统中的非线①性研究及仿真实验

利用分离信道的分步傅立叶法对信道间距为0.8nm的8路10 Gbit/s波分复用色散补偿系统进行仿真实验，分析了在具有级联光放大器系统中光纤色散和各种非线性效应（自相位调制SPM、交叉相位调制XPM、四波混频FWM）对系统传输的影响。仿真结果表明，在色散补偿WDM通信系统中，SPW对系统传输造成的损伤最大。并且由于非线性效应、传输损耗及噪声的综合影响，应当选取合适的系统输入功率。     

预啁啾对偏复用孤子技术的补偿

在导出自相位调制和交叉相位调制共同作用所致相位调制频率啁啾的基础上,数值研究了相位调制频率啁啾与初始啁啾的关系,并对有和无初始啁啾40Gbit/s归零码(RZ)在二阶和三阶色散完全补偿(路径平均色散为0)的色散管理偏振复用孤子传输系统中的传输效果进行计算。结果表明,在输入功率达到一定值时,初始啁啾参量C对相位调制频率啁啾的作用,决定着系统偏振复用孤子技术的成效及传输性能,适当选取初始啁啾参量C能够有效抑制偏振模色散,提高孤子脉冲稳定传输距离。     

DPSK色散管理孤子系统的稳定传输

DPSK调制方式和色散管理孤子(DMS)传输方案相结合的新的传输机制能抵制噪声和非线性损伤,在高速多通道光传输系统中具有突出优点。采用变分法研究同时存在光纤损耗、ASE噪声、孤子互作用等多种扰动因素的DPSK色散管理孤子系统的传输特性,在频域导频滤波控制方案下,导出了孤子各特征参数随传输距离的演化方程。对40 Gb/s长距离DPSK色散管理孤子系统的传输特性进行了数值模拟,其结果和理论分析一致。并通过Optisystem软件作进一步仿真,论证了该系统零频移稳定传输的可行性。     

色散管理孤子系统定时抖动的分析计算

利用两种方法研究了脉冲形状为高斯型的色散管理孤子系统定时抖动。利用微扰变分方法推导出光通信系统存在滤波器和自发辐射噪声的情况下,孤子参数演化的动力学方程,得出了定时抖动的表达式,并对其进行仿真,发现定时抖动来源于放大器噪声、频率偏移等,啁啾的符号和滤波器对系统总的定时抖动也有一定影响。再利用矩方法对色散管理孤子系统定时抖动进行了分析,两种方法得到的结果一致。     

强色散补偿高速光通信系统中的信道内非线性效应

研究了强色散补偿高速光通信系统中的自相位调制(SPM)、信道内交叉相位调制(IXPM)和信道内四波混频(IFWM)等非线性效应，分析了SPM所致脉冲对称扰动、IXPM所致定时抖动和IFWM所致振幅抖动的规律，并通过数值仿真实现了强色散补偿系统中1600km的稳定传输。     

强色散控制光传输系统中的信道内非线性效应

通过对非线性薛定谔方程的处理，推导了准线性系统中的相互作用方程，研究了强色散补偿光通信系统中的自相位调制、信道内交叉相位调制和信道内四波混频等非线性效应，分析了这些非线性效应所致脉冲对称扰动、定时抖动和振幅抖动的规律，并通过仿真实现了强色散控制系统中的稳定传输。     

同步幅度调制控制孤子系统中自发辐射噪声的影响

运用微扰法分析了幅度调制控制孤子系统中自发辐射噪声对系统传输特性的影响，考虑了补偿增益变化对系统自发辐射噪声的影响，得到了比较准确的结果。发现补偿增益明显影响孤子到达时间的抖动。     

具有滑频滤波器的光孤子通信系统时间抖动的研究

本文通过微扰理论，对采用滑频滤波器控制的孤子系统的时间抖动进行了研究。结果表明，滑频滤波器的引入，导致幅度和频率、幅度和滑频滤波器三阶项间的耦合，使得孤子传输系统的时间抖动增大，影响系统的传输极限。研究了滑频滤波器三阶项对滑频速率的影响，讨论和比较了具有滑频滤波器、固定频率滤波器和不加任何控制时的系统对由放大器的ＡＳＥ噪声产生的时间抖动的抑制结果。采用滑频滤波器是一种较好地抑制时间抖动的方法。     

色散补偿方式对相位调制系统中相位噪声的影响

分别推导了相位调制系统中采用色散预补偿方式和后补偿方式下非线性相位噪声的计算公式,基于此对这两种色散补偿方式下的相位噪声、功率容限以及最优信号峰值功率进行了详细的分析和讨论,结果表明:采用色散预补偿方式较后补偿方式能更有效地抑制非线性相位噪声,其对非线性相位噪声的抑制能力随着信号能量、放大自发辐射(ASE)的功率谱密度以及传输距离的增加而提高;同时,色散预补偿系统具有更高的功率容限;色散的作用使系统的最优信号峰值功率增大,最佳相移大于1rad;色散预补偿系统的最优信号峰值功率大于色散后补偿系统。     

Performance analysis of an optical serial-to-parallel converterwith erbium-doped fiber amplifier

In this paper, we develop a performance analysis of an surface-emitting second harmonic generation (SESHG) optical serial-to-parallel converter using an erbium-doped fiber amplifier (EDFA) as a preamplifier. The analysis is complicated by the fourth-order nonlinearity that acts on the signal plus amplified spontaneous emission (ASE) noise to create many beat noises at the binary decision device. However, we demonstrate that Gaussian approximation for the beat noise statistics is reasonable. We calculate the BER of the system as a function of the SHG nonlinear cross section (A^NL), EDFA gain, the bandwidth of the optical filter that band-limits the ASE noise, and the timing pulse-to-data pulse power ratio. We find that for reasonable values of these and other parameters, the EDFA/SESHG serial-to-parallel converter combination should be able to operate at or below a BER of 10^-12. We find that small increments (0-2 dB) in the signal power that is input to the EDFA are enough to compensate the effects of ASE noise for most of the parameter variations we consider. From this point of view, the ASE noise has little effect on system performance. However, when the input power is fixed, we show evidence in terms of BER that the ASE noise plays a significant role, particularly in the high A^NL, high gain case. Also in this case, we show that the optimal timing pulse-to-data pulse power ratio is somewhat different from the value that is optimal for the system without an EDFA     

基于高精细度F-P滤波器的40Gb/s全光时钟提取

提出了一种基于高精细度Fabry-Perot(F-P)滤波器的全光时钟提取方案,并进行了实验验证。为了实现对信号波长无关的特性,系统利用光纤中交叉相位调制(XPM)效应对输入信号进行正码波长变换,使变换后的波长始终与F-P滤波器的透射峰精确对准。采用精细度为1 012的高精细度F-P滤波器提取时钟,并利用半导体光放大器(SDA)的自增益调制(SGM)效应进一步抑制时钟信号的低频噪声,保证了高质量的时钟输出。实验中,利用这种装置对40 Gb/s归零(RZ)码信号进行了时钟提取,得到了抖动为285 fs的高质量40 GHz时钟信号,验证了方案的可行性。     

采用PSO算法的S波段EDFA的优化设计

成功地使用粒子群优化(PSO)算法优化设计了多级S波段EDFA,仿真结果表明,输入信号功率为-20 dBm时在1486～1520 nm可实现平坦增益,两级泵浦总功率为380 mW,平均增益可达10 dB以上,增益平坦度小于0.1 dB,噪声系数小于5 dB,满足WDM/DWDM系统的需求.另外,还重点对插入长波长ASE...     

Analysis of downlink power control and cooperation scheme for two‐tier heterogeneous cellular network

The traditional cellular network cannot keep pace with the dramatic growth in data traffic due to exponentially increasing number of multimedia applications and mobile subscribers. Recently, femto base stations (FBSs) are deployed with the macro base station (MBS) tier for off‐loading the data traffic and to improve the indoor coverage of the heterogeneous cellular network. However, FBS deployment also increases the cross‐tier interference of the heterogeneous cellular network resulting in outage performance degradation of MBS tier. This work develops an analytical framework to limit the cross‐tier interference of MBS tier using power control scheme (PCS). The proposed PCS works on path loss inversion and location‐based power level rule for FBS. Moreover, a cooperation scheme and an association policy with MBS (CSAPM) are introduced to improve the outage performance of the FBS tier. Tools from the stochastic geometry are used for deriving the signal to interference and noise ratio outage probability, total outage probability, and area spectral efficiency (ASE) of MBS tier and FBS tier. Additionally, ASE maximization problem is formulated to evaluate the optimal density of FBSs. The effectiveness of the proposed PCS and CSAPM on outage performance and ASE are numerically demonstrated. It is noted from the results that the proposed CSAPM can compensate the loss in outage performance of FBS tier due to PCS. Finally, simulation results validate the analytical results.     

Power penalty assessment in optically preamplified receivers witharbitrary optical filtering and signal-dependent noise dominance

The assessment of the power penalty of optically preamplified receivers with signal-dependent noise (SDN) dominance is often accomplished by neglecting the influence of the optical filtering of the amplified spontaneous emission (ASE) noise on the signal-ASE beat noise. In this paper, it is shown that the optical filtering of the ASE noise can have a strong impact on the signal-ASE beat noise and remarkably affect the power penalty, even for optical filter bandwidths five times wider than the signal bandwidth. A simple expression to analytically evaluate the power penalty due to optical filtering, which describes reasonably well the influence of the optical filter on the signal-ASE beat noise variance, is proposed. The accuracy of the new expression is investigated, in the case of assessment of the optical filter detuning impact on receiver performance and the case of optical filter bandwidth optimization, and its predictions are satisfactory in comparison with rigorous estimates. Two new expressions of power penalty due to extinction ratio and to eye closure are also presented. It is shown that the power penalty due to eye closure depends on the extinction ratio and vice versa. Our results show also that the power penalty due to eye closure is remarkably dependent on the eye closure asymmetry     

Power and dispersion constrained optimization of optical links with unequally-spaced repeater modules

The design optimization problem of optical component allocation for a point to point optical link is considered. A module that includes amplifiers and Dispersion Compensating Fiber (DCF) is utilized. Constraints of the problem that guarantee the feasibility of the search domain are analyzed. Constraints are defined to maintain and limit the power level of the signal and to control the accumulated signal dispersion generated along the link. The accumulated Amplified Spontaneous Emission (ASE) noise formulation of the extended model is analyzed. Based on the derivation, an algorithm is proposed to select the amplifiers and the DCFs so that the accumulated ASE noise along the link is minimized while the power and the dispersion are constrained. The proposed analysis and the algorithm simplify the process of finding the optimal configuration of point to point optical links and provide an optimized component allocation with an improved ASE noise performance. The optimal allocation found by our method, provides an ASE noise value that outperforms two experiments with 100,000 and 1,000,000 sample feasible allocations. The optimal solution is found by applying a very simple selection method and satisfies the problem constraints.