Investigations on order and width of RZ super Gaussian pulse in pre-, post- and symmetrical-dispersion compensated 10 Gb/s optical communication system using standard and dispersion compensating fibers

We show the effect of varied order and width of super Gaussian pulse at 10 Gb/s in dispersion compensated optical communication system. The optical communication system consists of standard single-mode fiber of 16 ps/nm/km of a certain length, whose dispersion is compensated using pre-, post- and symmetrical-dispersion compensation schemes with proportionate length dispersion compensating fiber of −80 ps/nm/km. Performance of these three compensation schemes is compared at 14 dBm values of Er-doped fiber amplifiers (EDFA) power at 1st, 2nd and 3rd order RZ super Gaussian optical pulse. The pulse width, full width at half maximum (FWHM) is also varied from 5 to 30 ps to highlight the optimum performance. The graphical results obtained show a relationship among the attributes pulse width, order of RZ super Gaussian optical pulse and dispersion compensation scheme implemented. It shows that to decrease BER and timing jitter in the system, smaller width and 3rd order super Gaussian pulse should be used. It is recommended that to decrease dependency of BER and timing jitter in the communication system on the pulse width i.e. FWHM, the symmetrical compensation scheme should be implemented.     

考虑非线性效应的路由与波长分配算法

本文研究了在波长路由的智能光网络中选择路由与波长分配(RWA)过程中如何考虑非线性效应的影响.在简要分析了考虑非线性效应影响的必要性后,以交叉相位调制为例推导出了一种简单的计算非线性效应引起的光功率代价计算公式,并讨论了如何将其引入路由与波长分配算法中.仿真结果表明非线性效应确实对RWA的优化结果产生一定的影响,其程度与物理拓扑、业务需求和具体的网络传输参量有关.     

Performance comparison of pre-, post- and symmetrical-dispersion compensation techniques using DCF on 40 Gbps OTDM system for different fibre standards

Various factors like polarization mode dispersion, non-linear effects, Kerr effect, second and third order dispersion impose limit on the performance (transmission distance, pulse broadening) of Optical Time Division Multiplexed (OTDM) transmission system. In this paper, the performance comparison of 40 Gbps OTDM transmission system with pre-, post-, and symmetrical-dispersion compensation techniques for different fibre standards has been carried out. It has been observed that for pre compensation, ITU 655 [D = 3.78 ps/nm/km] came to be best suitable fibre with the dispersion compensating fibre length of 2.36 km for maximum reach of 3000 km. For post- and symmetrical-compensation, the behaviour of alcatel [D = 8 ps/nm/km] is almost similar with maximum transmission distance of 3200 and 3050 km respectively.     

室内可见光无载波幅度相位调制系统性能分析

针对室内可见光通信调制技术问题,提出翻转光无载波幅度相位调制和单极性光无载波幅度相位调制两种功率有效的调制方案,二者分别采用"正、负模块极性分组"以及"零值位置极性编码"方法实现信号单极性处理,以满足可见光通信"强度调制/直接检测"的要求.基于朗伯辐射模型,考虑到高斯背景光噪声的可见光直射传输信道,推导了包括直流偏置光无载波幅度相位调制在内的三种调制方案的误比特率闭式表达式,仿真验证了其准确性.在此基础上,分析比较了三者频带利用率,讨论了信道参量对光无载波幅度相位调制系统误码性能的影响,结果表明,在5m×5m×3m的室内场景下,与发射机辐射角为30°和45°相比,0°时的系统误码性能分别优于6.9dB和29.9dB;收发机距离为1m时,误码性能比2m时改善近12dB.     

Investigation of Hybrid Optical Amplifiers for Dense Wavelength Division Multiplexed System with Reduced Spacings at Higher Bit Rates

Abstract

This article proposes various combinations of optical amplifiers for a dense wavelength division multiplexed system and investigates the impact of reduced channel spacing at high bit rates in terms of quality factor, bit error rate, eye closure, and output power. It is reported that the hybrid optical amplifier (Raman–erbium-doped fiber amplifier [EDFA]) provides better results with a maximum covered single span distance (220 km) at channel spacing of 6.25 GHz. The maximum acceptable bit rate for the 12.5-GHz channel spacing dense wavelength division multiplexed system is also investigated, and the recommendation is provided that for the Raman–EDFA, Raman–EDFA–Raman, EDFA–Raman–EDFA, and EDFA–semiconductor optical amplifier–EDFA, the operating bit rate should not be greater than 20, 16, 19, and 20 Gbps, respectively.     

Integrability,multi-soliton and rational solutions,and dynamical analysis for a relativistic Toda lattice system with one perturbation parameter

Under investigation in this paper is a relativistic Toda lattice system with one perturbation parameter α abbreviated as RTL_(α) system by Suris, which may describe the motions of particles in lattices interacting through an exponential interaction force. First of all, an integrable lattice hierarchy associated with an RTL_(α) system is constructed, from which some relevant integrable properties such as Hamiltonian structures, Liouville integrability and conservation laws are investigated. Secondly, the discrete generalized(m, 2 N-m)-fold Darboux transformation is constructed to derive multi-soliton solutions, higher-order rational and semirational solutions, and their mixed solutions of an RTL_(α) system. The soliton elastic interactions and details of rational solutions are analyzed via the graphics and asymptotic analysis. Finally, soliton dynamical evolutions are investigated via numerical simulations,showing that a small noise has very little effect on the soliton propagation. These results may provide new insight into nonlinear lattice dynamics described by RTL_(α) system.