信号调制延时光反馈混沌系统的多路复用通信

为了研究信号调制延时的光反馈与光注入半导体激光器激光混沌系统的多路复用通信,采用数值仿真的方法,通过支路用户信号对相应支路延时进行调制实现对信号的编码,然后利用混沌同步和互相关检测进行解码,成功实现了3个用户1Gbit/s信号的复用与解复用,分析了有效解码的条件及产生误码的主要原因。这一结果对于探讨用户数量更多、传输速率更快的混沌复用通信是有帮助的。     

非相干光反馈的半导体激光器混沌保密通信性能分析及其仿真

首先研究了非相干光反馈同步系统内部参数失配对系统同步性能的影响,并与相干光反馈的完全同步系统以及广义同步系统进行了比较,其次研究了非相干光反馈采用三种不同的信号调制解调方式(CSK,CMS,ACM),对三种不同频率(250 MHz,2.5GHz和12.5GHz)的信号进行了调制解调。通过MATLAB仿真实验可知,非相干光反馈混沌同步系统相对于相干光反馈完全同步系统更易于实现,同时保留了一定的对参数失配的敏感特性,从而确保了该系统比相干光反馈广义同步具有更高的安全性;在信号解调时,CSK只能解调出250MHz信号,CMS能解调出2.5GHz信号,ACM能够解调出高达12.5GHz的信号。     

单环掺铒光纤激光器的延时反馈-注入混沌同步

利用延时反馈-注入法研究了具有泵浦光强调制的单环掺饵光纤激光器的混沌同步.数值模拟表明,在合适的反馈和注入条件下,两个单环掺铒光纤激光器能够达到混沌同步.即使存在一定的高斯噪声影响,两个激光器仍然能够达到较好的同步.在此基础上,进一步研究了掺铒光纤激光器中参数不匹配情况对混沌同步的影响.     

偏振选择互注入半导体激光器的混沌同步

研究了偏振选择互注入条件下半导体激光器的同步和混沌滤波效应。将单模互注入速率方程扩展为包含两个偏振态的理论模型,并选择X偏振态作为互注入形式,不仅为激光器产生混沌和实现同步提供了条件,还可以完全抑制Y偏振光,实现了纯偏振模式同步。通过频率失调的引入,保持了激光器主从地位的稳定。研究结果表明,主从激光器实现了时差等于注入延时的混沌同步,输出功率表现出高频振荡并伴随有对称性破坏现象。对主激光器进行调制时,同步系统表现出与单向注入相似的混沌滤波效应;对从激光器进行调制时,系统的混沌滤波效应并不明显。     

延时光电反馈法实现半导体激光器的混沌控制

采用延时光电反馈法实现了半导体激光器的混沌控制.首先通过数值计算激光器的动力学方程,绘制了系统的最大李雅普诺大(Lyapunov)指数随注入电流调制强度的变化曲线,确定了激光器处于混沌态的参数区间[0.51,0.60].然后利用延时光电反馈方案实现了激光器的混沌控制.数值模拟表明,这种方案能够实现两类不同的混沌控制.第一,能将系统由混沌态控制到其固有的周期态,这类控制不改变系统原有的动力学行为;实现稳定控制以后,控制信号可以趋近于零,激光器的周期输出不需要控制信号来维持;第二,能将系统南混沌态控制到新的周期态,这类控制改变系统原有的动力学行为;实现稳定控制以后,控制信号不可以趋近于零,激光器的周期输出需要控制信号来维持.     

半导体激光器混沌电路延时反馈控制方法

由于当前方法未能建立物理模型,导致混沌电路延时反馈控制复杂度和控制耗时增加,容错率下降,为此提出一种半导体激光器混沌电路延时反馈控制方法。组建半导体激光器混沌电路延时反馈条件下激光器电流激发混沌的物理模型,获取激光器非线性增益和线宽增强因子特性,并获取控制延迟可控条件。分析延迟量和反馈增益的解析关系,获取目标周期轨道控制参数的分岔图,以此为依据进行半导体激光器混沌电路延时反馈控制。实验结果表明,所提方法能够有效降低混沌电路延时反馈控制复杂度和控制耗时,大幅度提升容错率。     

纤激光器延时反馈的动态特性与复杂度研究

基于双环掺Er3+光纤激光器,提出一种输出变量延时自反馈混沌控制的模型.通过加入可变光延时器和光耦合器控制光纤激光器的输出状态,系统输出信号经历了周期态、多周期态和混沌态.利用排列熵箅法,研究光纤激光器输出信号复杂度随反馈延时时间的变化趋势.与分岔图相比较后发现,系统复杂度的变化更能准确地检测系统的动态行为,而且能区分...     

半导体激光器的混沌驱动同步

利用混沌驱动同步法研究了在电流调制下的半导体激光器的混沌同步。首先数值计算了系统最大Lyapunov指数随调制强度的变化情况,确定了激光器处于混沌态的参数区间。然后分别实现了同地激光器系统和异地激光器系统的混沌驱动同步。响应激光器间相关系数的数值计算表明,两种激光器系统均能达到很好的混沌同步。以三个响应激光器为例,将响应系统推广到多个激光器,并且实现了两种激光器系统的混沌同步。     

利用耦合时延增强激光混沌系统安全性能研究

安全性是混沌通信中的重要问题。基于一个外光反馈半导体激光器驱动两个互耦合激光器的混沌通信系统,研究激光混沌系统中反馈时延与耦合时延特征,并应用龙格-库塔法进行动态仿真。重点分析了当调节一些可控参数(耦合时延和驱动强度)时,能够改变两耦合激光器输出自相关函数中反馈时延和耦合时延幅值的差异,以此掩藏反馈时延,从而得出更优载波。仿真结果说明利用耦合时延可以增强激光混沌系统的安全性。最后给出了在优化载波后系统同步质量的讨论。     

激光耦合同步及其在光纤混沌保密通信中的应用

本文建立了光纤混沌保密通信耦合同步系统模型,实现了外部光注入分布反馈半导体激光器激光混沌在长距离光纤传输中的耦合同步,证明了光纤的交叉相位调制是限制激光混沌在光纤传输中同步的主要原因,导出了这种传输的极限.该同步系统在长距离光纤混沌模拟和数字保密通信中的数值模拟表明,该系统确有较高的保密性能和反破译能力.光纤混沌保密通信是可以实现的.     

Dynamic regimes in semiconductor lasers subject to incoherent optical feedback

The dynamics of a semiconductor laser subject to polarization-rotated (incoherent) optical feedback in the long cavity limit has been numerically and experimentally investigated. The results show that the induced dynamics can be grouped into four regimes (stable, chaotic, pulsed, and two state) and that the transverse-magnetic mode of the laser never lases in the ring cavity configuration studied. In addition, unlike the earlier short-cavity work, the boundaries between the regimes in the long-cavity case were found to be independent of the external-cavity delay time.     

Characteristics of chaos synchronization in semiconductor lasers subject to polarization-rotated optical feedback

We numerically investigate the detailed characteristics of chaos synchronization in semiconductor lasers subject to polarization-rotated optical feedback. The emission of the dominant TE mode of a drive laser is rotated 90 deg and fed back to the laser with time delay. The polarization-rotated TE mode is also injected with time delay into the TM mode of a second laser. Two types of synchronization with different time-lags are found, as in the case for synchronization in semiconductor lasers with nonrotated optical feedback. However, a significant difference to the nonrotated optical feedback case is that neither of the two types of synchronization requires matching of optical carrier frequency between the two lasers.     

Phase-induced intensity noise in digital incoherent all-optical tapped-delay line systems

In this paper, the authors analyze conditions under which they can be certain on the intensity addition of a given device, such as tapped-delay lines, used in digital incoherent all-optical communication systems. A general expression for phase-induced intensity noise that is applicable to all types of semiconductor lasers is derived by defining an optical self-SNR expression that can be used to analyze and measure phase-induced intensity noise. The result shows that in order to have a minimal phase-induced intensity noise in most digital optical incoherent systems, a large optical self-SNR, e.g., 20 dB or more, is needed. This in turn is shown to place a limit on the maximum rate of processing in a typical incoherent optical system even neglecting the bandwidth limitation of the photodetector. Furthermore, it is shown that the maximum rate of processing depends on the laser autocorrelation function and laser coherence time.     

Synchronized chaotic optical communications at high bit rates

Basic issues regarding synchronized chaotic optical communications at high bit rates using semiconductor lasers are considered. Recent experimental results on broadband, high-frequency, phase-locked chaos synchronization, and message encoding-decoding at 2.5 Gb/s are presented. System performance at a bit rate of 10 Gb/s is numerically studied for the application of three encryption schemes, namely chaos shift keying, chaos masking, and additive chaos modulation, to three chaotic semiconductor laser systems, namely the optical injection system, the optical feedback system, and the optoelectronic feedback system. By causing synchronization error in the forms of synchronization deviation and desynchronization bursts, the channel noise and the laser noise both have significant effects on the system performance at high bit rates. Among the three laser systems, the optoelectronic feedback system has the best performance while the optical feedback system has the worst. Among the three encryption schemes, only the performance of additive chaos modulation with low-noise lasers is acceptable at high bit rates.     

外部光反馈对强耦合外腔半导体激光器特性影响的理论分析

本文从理论上分析了外部光反馈对强耦合外腔半导体激光器特性的影响，对相干外部光反馈和非相干外部光反馈两种情形的分析结果均表明强耦合外腔半导体激光器可将半导体激光器所能容忍的临界光反馈强度提高大约２０ｄＢ以上，同时得出了长外腔和强耦合有利于提高外腔半导体激光器抗反馈能力的结论。     

Beat interference penalty in optical duplex transmission

The near- and far-end source spectra in optical full duplex systems can heterodyne, producing a high level of beat interference noise in the receiver bandwidth. This is called coherent common-channel crosstalk, the penalty from which is found in addition to that from incoherent near-end crosstalk (NEXT) quantified in an earlier publication. We find most directly modulated high-chirp laser systems, such as those using single-mode distributed feedback lasers or multimode Fabry-Perot (FP) lasers, are relatively immune to coherent NEXT for speeds up to 100 Mb/s. In the transform limit, however, which occurs at high bit rates or low chirp, the maximum allowable NEXT must be decreased by as much as 20 dB, compared to the incoherent case. One solution is to use uncooled single-mode lasers separated by a small wavelength spacing (20 nm, for example) as popularized for the coarse wavelength division multiplexing (WDM) grid     

WDM光网络系统相干串扰与非相干串扰

同频串扰可以分为相干串扰与非相干串扰,本文提出了WDM光网络系统串扰相干性分析的数学模型,分析提出了相等的相干串扰代价和非干串扰代价下引起的WDM光网络系统功率代介的一致性,并与模拟相干串扰和非相干串扰结果进行了比较验证。实验结果表明,对应1dB功率代价下,WDM光网络系统对应相干串扰和非相干串扰代价容限步于－20dB和理论结果一致。串扰对于网络规模有一定的限制。