State estimation and synchronization of pendula systems over digital communication channels

The recent results on nonlinear systems synchronization and control under communication constraints are applied to the remote state estimation and synchronization for a class of exogenously excited nonlinear Lurie systems. State estimation of the chain of diffusively coupled pendulums over the digital communication channel with limited capacity is experimentally studied. Advantage of the adaptive coding procedure under the conditions of the plant model uncertainty and irregular disturbances is shown. Quality of the estimation is evaluated by means of the experiments with the multi-pendulum set-up. Experimental study of master-slave synchronization over network (local network, wireless network) for the system with two cart-pendulums is presented.     

Suppression of nonlinear effects by phase alternation in strongly dispersion-managed optical transmission

The nonlinear effects of amplitude jitter and ghost pulse generation, which are present in strongly dispersion-managed optical communication systems can be suppressed by alternation of the phase of the bits. A physical explanation for this effect is given that shows that with suitably chosen phase modulations the processes that give rise to the nonlinear effects will counteract each other.     

混沌通信系统中非线性信道的自适应神经Legendre正交多项式均衡

针对混沌通信系统中非线性信道干扰问题，基于混沌信号重构理论和Legendre正交多项式结构，提出了一种自适应神经Legendre正交多项式信道均衡器，并给出相应的归一化最小均方算法. 仿真研究表明：所提出的自适应神经Legendre正交多项式信道均衡器能有效地消除线性和非线性信道干扰，均衡器输出信号能反映出混沌信号的特性，具有良好的抗干扰性能.该均衡器的结构简单，权系数参数较少，收敛稳定性较好. 关键词： Legendre 正交多项式 信道均衡 混沌吸引子 神经网络     

Symbolic-computation study of the perturbed nonlinear Schrödinger model in inhomogeneous optical fibers

A realistic, inhomogeneous fiber in the optical communication systems can be described by the perturbed nonlinear Schrödinger model (also named as the normalized nonlinear Schrödinger model with periodically varying coefficients, dispersion managed nonlinear Schrödinger model or nonlinear Schrödinger model with variable coefficients). Hereby, we extend to this model a direct method, perform symbolic computation and obtain two families of the exact, analytic bright-solitonic solutions, with or without the chirp respectively. The parameters addressed include the shape of the bright soliton, soliton amplitude, inverse width of the soliton, chirp, frequency, center of the soliton and center of the phase of the soliton. Of optical and physical interests, we discuss some previously-published special cases of our solutions. Those solutions could help the future studies on the optical communication systems.     

混沌通信系统中非线性信道的自适应组合神经网络均衡

针对混沌通信系统的非线性信道干扰问题,基于混沌信号重构理论和函数型连接神经网络理论,提出了一种横向滤波器与函数型连接神经网络组合(combination of transversal filter and functional link neural network,CFFLNN)的自适应非线性信道均衡器,并给出基于低复杂度归一化最小均方(NLMS)的自适应算法,并对该均衡器的稳定性以及收敛条件进行了分析.该非线性自适应均衡器充分利用了横向滤波器的快速收敛,以及函数型连接神经网络通过增大输入空间提高非线性逼近能力的特点,进一步提高均衡器的收敛速度和降低稳态误差.仿真研究表明：所提出的非线性自适应均衡器能够有效地消除线性和非线性信道干扰,均衡器输出信号能反映出混沌信号的特性,具有良好的抗干扰性能;且该均衡器的结构简单,收敛稳定性较好,易于工程实现. 关键词： 非线性信道 自适应均衡器 混沌吸引子 神经网络     

Theoretical investigations of low-noise regeneration of light pulses in communication systems

The properties of an optical repeater consisting of a nonlinear amplifier and a saturable absorber have been calculated. The repeater is to compensate for both pulse damping and broadening in a glass fiber communication link. The results lead to the conclusion that the optical repeater meets the requirements for its employment in communication systems, especially at high bit rates.     

Communication with a chaotic traveling wave tube microwave generator

Traveling wave tubes (TWTs) are vacuum electronic amplifiers (see Beck, Gittins, and Pierce) that are commonly used for communication in the centimeter wavelength range. Increasing demand for high data flow in wireless communication systems (satellite communication systems are a good example) raises needs for making TWT's more compact and efficient. Motivated by this we suggest a scheme in which a TWT with feedback is operated in a highly nonlinear regime where the device behaves chaotically. The chaos is controlled using small controls. Then, at the receiving end a receiving TWT synchronizes to the chaotic transmitter and amplifies the received signal with nearly no distortion. Results on numerical simulations of the proposed scheme are reported and used to evaluate its effectiveness.     

SC混沌比例投影同步方法在保密通信中的应用

利用基于线性稳定性准则的SC混沌比例投影同步方法,提出一种应用于保密通信的混沌掩盖方案.适当分离出混沌系统的线性项与非线性项,构造一个非线性驱动向量函数,混沌状态变量包含用于投影同步的比例因子,把所需传递的有用信息掩盖入其中一个分量上,得到混沌载波信号,提高加密信息的复杂度和解码的困难度.以Lorenz吸引子和超混沌Rössler吸引子为例进行数值仿真,详细分析传输的正弦信息加密解密全过程,给出简单、最优的混沌掩盖方案,数值分析证明比例投影同步方法应用于保密通信领域的有效性.     

Model-based predictive controller design for a class of nonlinear networked systems with communication delays and data loss

This paper discusses the model-based predictive controller design of networked nonlinear systems with communication delay and data loss. Based on the analysis of the closed-loop networked predictive control systems, the model-based networked predictive control strategy can compensate for communication delay and data loss in an active way. The designed model-based predictive controller can also guarantee the stability of the closed-loop networked system. The simulation results demonstrate the feasibility and efficacy of the proposed model-based predictive controller design scheme.     

Dual phase and dual anti-phase synchronization of fractional order chaotic systems in real and complex variables with uncertainties

In the present article the nonlinear control method is used for dual phase and dual anti-phase synchronizations among fractional order chaotic systems with uncertainties. The control functions are designed to achieve synchronization with the help of nonlinear control technique. The nonlinear control method is found to be very effective and convenient to achieve dual phase and dual anti-phase synchronization with parametric uncertainties of the non-identical chaotic systems. The fractional order real and complex chaotic systems with parametric uncertainties are taken to illustrate dual phase and dual anti-phase synchronization process. Numerical simulation results show the possibility of dual phase and dual anti-phase synchronizations, which are carried out using Adams–Bashforth–Moulton method and graphical results are presented to display the effectiveness of the method. The striking feature of the article is the graphical demonstration of fast communication through signals between transmitter and receiver for the complex variable systems compared to the real variable systems.     

Nonlinear effects in optical fibers

The basic differential equations necessary to represent nonlinear propagation of short and ultrashort optical pulses in dielectric waveguides are derived. After introducing fundamental and higher-order soliton solutions of the nonlinear Schroedinger equations, the possibilities of realizing soliton-based communication systems are discussed. Higher-order nonlinear effects associated with selj-Raman gain and optical amplification in connection with the use of active fibers are also described.     

High-speed underwater wireless optical communications: from a perspective of advanced modulation formats [Invited]

In this paper, recent advances in underwater wireless optical communication(UWOC) are reviewed for both LED-and LD-based systems, mainly from a perspective of advanced modulation formats. Volterra series-based nonlinear equalizers, which can effectively counteract the nonlinear impairments induced by the UWOC system components, are discussed and experimentally demonstrated. Both the effectiveness and robustness of the proposed Volterra nonlinear equalizer in UWOC systems under different water turbidities are validated.To further approach the Shannon capacity limit of the UWOC system, the probabilistic constellation shaping technique is introduced, which can overcome the inherent gap between a conventional regular quadrature amplitude modulation(QAM) format and the Shannon capacity of the channel. The experimental results have shown a significant system capacity improvement compared to the cases using a regular QAM.     

The decoupling of damped linear systems in configuration and state spaces

It has recently been reported that any viscously damped linear system can be decoupled in the configuration space by a real, nonlinear, time-dependent transformation. The purpose of this rapid communication is to provide a few clarifying remarks about the decoupling operation. It is shown that, for homogeneous systems, the time-dependent configuration-space decoupling transformation is real, linear and time-invariant when cast in state space. In addition, the configuration-space transformation generates a diagonalizing structure-preserving transformation. In non-homogeneous systems, both the configuration and associated state transformations are nonlinear and depend continuously on the excitation. An example is given of a linear system that can be decoupled in configuration but not in state space.     

Intra-channel nonlinearities mitigation in pseudo-linear coherent QPSK transmission systems via nonlinear electrical equalizer

A novel nonlinear electrical equalizer (NLEE) based on Volterra theory is proposed for mitigating intra-channel nonlinearities in pseudo-linear coherent optical communication systems. According to the temporal matching condition of intra-channel nonlinear pulse interactions, we just select specific nonlinear terms and reduce the computation complexity considerably. Numerical simulations of 10GBaud coherent quadrature phase-shift keying (QPSK) transmission show that the simplified NLEE can efficiently mitigate intra-channel nonlinearities.     

Control of interaction between femtosecond dark solitons in inhomogeneous optical fibers

In this paper, we present exact femtosecond one- and two-dark soliton solutions for a variable-coefficient higher-order nonlinear Schrödinger equation via modified Hirota method. The propagation and interaction of femtosecond dark solitons are investigated in inhomogeneous fiber systems. Elastic collision, bound oscillation and parallel propagation can be achieved in both Gaussian distributed parameter system and exponentially periodic distributed parameter system by choosing the appropriate distributed parameters and soliton parameters. The results may be beneficial to the realization of interaction control of femtosecond dark solitons in communication systems.     

Generation and dynamics of ghost pulses in strongly dispersion-managed fiber-optic communication systems

We investigate the nonlinear generation and dynamics of ghost pulses in high-speed strongly dispersion-managed fiber-optic communication systems. Particular consideration is given to the importance of system parameters for the properties of the emerging ghost pulses. Conclusions are drawn about the growth rate and the temporal position of the ghost pulses in different systems.     

All-optical method for maintaining a fixed intensity level of a light signal in optical computation

In data and image processing the role of optics is already well established. Due to inherent parallelism the optical systems run faster than its electronic counterparts. Optical nonlinear material can be used as a successful optical switch. The primary requirement for proper functioning of such nonlinear material based logic devices is a fixed intensity level of the optical signal against a specific logic state. In this communication, the authors propose a new concept to obtain a fixed intensity level of optical signal against a specific logic state for data processing. The scheme may extend a tremendous application not only to the area of all-optical computation, but also to optical communication process.     

Fiber Nonlinearities: A Tutorial

Fiber nonlinearities have long been regarded as being mostly harmful for fiber-optic communication systems. Over the last few years, however, the nonlinear effects are increasingly being used for practical telecommunications applications,the Raman amplification being only one of the recent examples. In this tutorial I review the vario us nonlinear effects occurring in optical fibers from both standpoints..     

Dynamic control and information processing in chemical reaction systems by tuning self-organization behavior

Specific external control of chemical reaction systems and both dynamic control and signal processing as central functions in biochemical reaction systems are important issues of modern nonlinear science. For example nonlinear input-output behavior and its regulation are crucial for the maintainance of the life process that requires extensive communication between cells and their environment. An important question is how the dynamical behavior of biochemical systems is controlled and how they process information transmitted by incoming signals. But also from a general point of view external forcing of complex chemical reaction processes is important in many application areas ranging from chemical engineering to biomedicine. In order to study such control issues numerically, here, we choose a well characterized chemical system, the CO oxidation on Pt(110), which is interesting per se as an externally forced chemical oscillator model. We show numerically that tuning of temporal self-organization by input signals in this simple nonlinear chemical reaction exhibiting oscillatory behavior can in principle be exploited for both specific external control of dynamical system behavior and processing of complex information.     

The nonlinear dynamical stabilization of ps-pulses in gradient index optical fibres

The new possibilities of controlled nonlinear evaluation of short pulses in gradient index optical fibres, connected with the fundamental and higher modes of the fibre geometry and with the pulse envelope are analysed. The possibilities for using these phenomena for increasing the quantity of information transmitted by such pulses are discussed. The preferred regions for employment of both soliton and non-soliton powerful pulses in optical communication systems are identified.