一种改进的ISFA信道估计算法

设计了一种基于符号内频域平均(ISFA)的信道估计算法,用于偏振复用光正交频分复用(PDM-O-OFDM)系统的信道估计和传输信道色散损伤的均衡。算法采用凯撒窗函数对基于导频的ISFA算法进行改进,提高了信道估计后处理的精度,改善了长距离PDM-O-OFDM系统的误码率(BER)和光信噪比(OSNR)性能。通过仿真试验,确定了算法的相关参数,分析了算法对长距离系统中色散损伤的均衡性能。仿真结果表明,改进算法对于传输距离超过700km系统的均衡效果优于原算法,其中900km处的OSNR代价比原算法低0.35dB。     

一种降低CO-OFDM系统PAPR改进的星座图扩展算法

相干光正交频分复用(CO-OFDM)系统中的较大峰值平均功率比(PAPR)问题会导致严重的光纤非线性效应。本文提出了一种改进的星座图扩展(ACE)算法,取得了更好的PAPR抑制效果。研究表明,ACE算法与凸集投影法(POCS)相结合可减少计算复杂度,但存在峰值再生现象等问题。为此,本文利用抛物峰值抵消(PPC)算法改善迭代过程中的峰值再生现象,并采用星座映射预修正技术提高了收敛速度。采用改进算法对4QAM、29 Gb/s的CO-OFDM系统进行了仿真实验,结果表明改进算法使OFDM信号的PAPR降低了4.41 dB,并且具有更快的收敛速度。     

基于SOA的平行双抽运结构偏振复用OFDM信号的全光波长变换

理论研究并模拟仿真了在半导体光放大器(SOA)中的基于平行双抽运结构的偏振复用十六进制正交幅度调制-正交频分复用(16QAM-OFDM)信号的全光波长变换(AOWC)。理论推导及仿真结果表明偏振复用16QAMOFDM信号可以经过全光波长变换实现偏振不敏感信号无串扰直接接收,并对影响系统转换效率的因素,如频率间隔、SOA注入电流、信号光功率及信号光入射角等进行了分析,同时分析结果验证了理论推导的正确性。     

An IIR adaptive electronic equalizer for polarization multiplexed fiber optic communication systems

An electronic digital equalizer for polarization multiplex coherent fiber optic communication systems is designed to compensate polarization mode dispersion (PMD) and residual chromatic dispersion (CD) of transmission channel. The proposed equalizer is realized with fraction spaced infinite impulse response (IIR) butterfly structure with 21 feedforward taps and 2 feedback taps. Compared with finite impulse response (FIR) structure, this structure can reduce implementation complexity of hardware under the same condition. To keep track of the random variation of channel characteristics, the filter weights are updated by least mean square (LMS) algorithm. The simulation results show that the proposed equalizer can compensate residual chromatic dispersion (CD) of 1600 ps/nm and differential group delay (DGD) of 90 ps simultaneously, and also can increase the PMD and residual CD tolerance of the whole communication system.     

用于PMD补偿的判决反馈均衡器的结构研究

文章采用自适应均衡技术对偏振模色散(PMD)进行补偿,给出了判决反馈均衡器(DFE)结构,通过对前向均衡器(FFE)部分的改进,得到了适用于高速光纤通信系统的行波滤波器(TWF)及折叠级联的TWF结构,最后通过ADS仿真软件,得到了系统S参数仿真结果.     

PAPR reduction based on improved Nyquist pulse shaping technology in OFDM-RoF systems

High peak-to-average power ratio (PAPR) is the main disadvantage in orthogonal frequency-division multiplexing (OFDM) communication systems, which also exists in OFDM-radio over fiber (RoF) systems. In this paper, we firstly analyze the impact of high PAPR on a 40 GHz OFDM-RoF system, and then describe the theory of Nyquist pulse shaping technology for reducing PAPR. To suppress PAPR further, an improved Nyquist pulse shaping technology is proposed, in which the distribution of original-data amplitude is changed by properly selecting the time-limited waveforms of the different subcarriers. We firstly apply the improved Nyquist pulse shaping technology to an OFDM-RoF system. The simulation results show that PAPR is effectively reduced by more than 2 dB with the bit error rate (BER) declining by about 0.125%.     

光纤信道自适应均衡器的仿真研究

为了解决色散时光纤通信系统高速率、长距离传输的限制,在分析影响光纤通信系统性能的主要原因的基础上,提出一种光纤信道仿真模型,并用MATLAB仿真LMS算法和RLS算法对10 Gb/s光纤信道进行自适应均衡的性能.仿真结果表明,这两种算法简单、高效,能有效消除光纤色散和偏振模色散(PMD)引起的码间干扰,RLS算法比LMS计算复杂度高,但收敛速度更快,所以这两种算法都能满足光纤通信系统对均衡速度较高的要求.     

ICA在偏振复用系统信号分离中的应用

光纤偏振复用系统中两束偏振态相互正交的光在一根光纤中传输时,由于偏振模色散和偏振耦合等因素,会产生串扰。文章针对这一问题,将基于互信息最小化的ICA(独立分量分析)算法应用到光纤通信偏振复用系统输出信号的分离中。仿真结果表明,采用该方法在无需任何先验知识的情况下,可以很好地分离出原始信号。     

TD-LTE-Advanced系统中一种新型8天线双码本设计方法

提出了一种新型8天线双码本设计方法,有效提高了TD-LTE-Advanced系统频谱效率. 该方法根据层映射的层数对码本分组,层数为1、2及5~8时,利用R8协议中4天线码本的满秩矩阵生成码本;层数为3、4时,将离散傅里叶变换矩阵与循环延迟分集技术相结合构造新码本. 与R10协议中给出的8天线双码本相比,在反馈开销相同的情况下,新码本码字间距更大. 仿真结果表明,在8发2收层数为2的条件下,新码本增益提高2 dB以上;当信噪比为5 dB时,新码本比现有码本的频谱效率高15%以上.     

A method for nonlinearity compensation of OFDR based on polynomial regression algorithm

A method based on polynomial regression algorithm(PRA) is proposed in this paper to compensate the nonlinear phase noise in optical frequency domain reflection(OFDR) systems. In this method, the nonlinear phase of OFDR systems is represented by the polynomial phase function, and then the coefficients of the polynomial phase function are estimated by PRA. Finally, the nonlinearity is compensated by match Fourier transform(MFT). Simulation results demonstrate that the proposed algorithm has good performance in compensating both weak and strong nonlinear phase noises of OFDR systems.