基于USB的波分复用光传飞行控制系统的开发

针对飞行控制系统的特点,开发了一套基于USB的多路数字信号进行波分复用的光纤传输系统,以提高光传系统的传输速率.着重构建了光发射器、光接收器及光波分复用器的物理系统.在直升机显模型跟踪电传飞行控制系统(MFCS)的基础上,开发了直升机贴地飞行波分复用光传系统实时半物理仿真验证平台.通过光传与电传性能对比,验证了所开发系统的可行性,具有工程实用意义.     

波分复用在自由空间光通信系统的应用仿真

介绍波分复用和自由空间光通信系统原理,利用Optisystem光通信软件仿真搭建了波分复用在光传输链路系统的应用模型。在直接调制下,通过对系统的Q因子、误码率等参数的仿真分析表明,波分复用在FSO系统中的应用具有可行性和稳定性。     

DWDM在通信网中的应用

首先介绍通信设施使用多路利用技术的发展进程,然后叙述了波分复用在光纤传输线路中的应用,最后解释了波分复用在光核心网的应用。     

一种新型双向光波载波传输系统设计

提出并验证了一种新型的双向多路光载波传输系统,在阐述其原理的基础上构建了一个双通道波分复用传输系统,采用16-QAM-OFDM信号成功地实现了对下行信号强度重调制,并且进行了CATV/RoF/16-QAM-OFDM多路信号双向传输仿真实验。     

基于Optisystem的波分复用性能的仿真研究

分析了波分复用(WDM)技术及系统的设计原理,介绍了Optisystem软件强大的仿真功能.在此基础上,给出了基于Optisystem的波分复用光传输链路仿真模型的搭建,对复用及解复用后的光信号进行仿真得出光谱图,对链路传输性能及Q因子、误码率、眼图的等参数进行分析,并验证了波分复用系统的正确性和设计方案的可行性,近而得出相关结论.     

基于阵列波导光栅的波分复用器件

阵列波导光栅波分复用 /解复用器有 N个输入端口和 N个输出端口 ,能同时传输 N2 路不同的光信号 ,除具有波分复用和解复用功能外 ,能灵活地与其它光器件组成多波长激光器、光路分插复用器、光路交叉连接器、波长路由器等波分复用器件 ,在光通信网络中有着广泛的应用前景。     

基于阵列波导光栅的波分复用器件

阵列波导光栅波分复用／解复用器有N个输入端口和N个输出端口,能同时传输N^3路不同的光信号,除具有波分复用和解复用功能外,能灵活地与其它光器件组成多波长光源、光路分插复用器、光路交叉连接器、波长路由器等波分复用器件,在光通信网络中有广泛的应用前景。     

未来的WDM光传输网的若干新技术

信息流量的爆炸,给通信传输技术的发展带来了机会。波分复用（WDM）从其出现伊始,便以它的传输容量大、对高层协议和技术适应性强以及易于扩展等特点而备受欢迎。经过几年的应用和发展,早期的点到点的波分复用系统正在向点到多点、多点到多点乃至环状、网状光传输网演进。可以预计,这种基于波分复用的光传输网将会成为未来通信体系中的最主要的部分。本文将介绍几种适用于这种光传输网的新技术。宽带平坦增益光纤放大器用于波分复用系统的光纤放大器与应用于单信道光通信系统的光纤放大器不同,除了要能提供足够大的放大量以外,还必…     

超长距波分复用系统中混合光放大器的研究

采用理论分析和软件仿真的方法,研究了级联混合光放大器在超长距波分复用系统中的应用,在讨论单跨距混合光放大器工作原理的基础上,对级联混合光放大器的光信噪比及增益平坦等特性进行分析,设计了适用于ULH系统的高信噪比、动态增益平坦的混合光放大器系统,并结合实际的ULH应用案例进行了建模仿真.     

用于粗波分复用系统的拉曼光放大器

文章针对城域网中由于粗波分复用(CWDM)系统光功率预算受到限制而给组网应用带来的问题,介绍了一种针对宽工作波长范围的波分复用系统的拉曼光放大器及其关键技术,同时,给出了该光放大器在粗波分复用系统中的实测结果.     

Design and implementation of a hardware-in-the-loop simulation system for small-scale UAV helicopters

We present in the paper the design of a hardware-in-the-loop simulation framework and its actual implementation on our custom constructed unmanned-aerial-vehicle (UAV) helicopter systems. Real-time hardware-in-the-loop simulation is one of the most effective methods for the verification of the overall control performance and safety of the UAVs before conducting actual flight tests. In our proposed framework, four modules, which include onboard hardware, flight control, ground station and software, are integrated together to realize the hardware-in-the-loop simulation. This design is successfully utilized for simulating several flight tests including basic flight motions, full-envelope flight and multiple UAV formation flight. Results obtained show that the constructed hardware-in-the-loop simulation system is highly effective and useful.     

Coherent crosstalk in ultradense WDM systems

We present extensive numerical studies on the determination of coherent wavelength-division multiplexing (WDM) crosstalk penalties for ultradense wavelength-division multiplexed (DWDM) systems, focusing on carrier-suppressed return-to-zero (CSRZ) as well as on 67% duty cycle differential phase-shift keying (67% RZ-DPSK) at a spectral efficiency of 0.8 b/s/Hz. Our analyses reveal large statistical variations in the predicted required optical signal-to-noise ratio (OSNR) when changing the WDM channels' interference conditions, in particular their relative optical phases and their relative time shifts. The strong impact of the exact WDM interference conditions can lead to simulation inaccuracies of many decibels when using standard OSNR simulations techniques. In measurements of DWDM system performance, the long averaging time of bit error ratio (BER) test sets can hide these burst-error generating penalty variations, and may, therefore, lead to wrong interpretations, especially for systems employing forward error correction (FEC). To overcome the DWDM simulation problem, we introduce and thoroughly assess a new simulation technique that allows us to efficiently and accurately capture the average required OSNR penalty for DWDM systems with negligible statistical error.     

Performance Limitations of Subcarrier Multiplexed WDM Signal Transmissions Using QAM Modulation

We theoretically investigate the performance limitations of subcarrier multiplexed (SCM) wavelength-division-multiplexing (WDM) systems using optical double-sideband (DSB) modulated, 16-quadrature amplitude-modulated (QAM) signals. The performance limitations are investigated using crosstalk power and SCM channel spacing for various transmission conditions, including impairment factors such as dispersion and fiber nonlinearities for a single wavelength channel first. The effects of WDM channel spacing on SCM systems with multiwavelength channels are also evaluated via the calculated bit error rate (BER) performance, based on the performance limitations found in the single-wavelength simulation. This enables us to provide guidelines for the design of SCM/WDM systems for fiber-to-the-home (FTTH) network in WDM–passive optical network (PON) architecture, based on the performance limitations.      

Performance analysis under dynamic loading of wavelength continuous and non‐continuous WDM networks with shortest‐path routing

The performance of WDM networks using shortest path routing is studied under wavelength continuous (WC) and non‐continuous (NWC) constraints and dynamic traffic loading. Approximate analytical models are presented for the performance studies of such systems. Results of numerical calculations based on these models and simulations are given for different network topologies for the purposes of comparison. These analytical and simulation results are used to study the performance of these WDM networks under dynamic traffic loading. Copyright © 2001 John Wiley & Sons, Ltd.     

Transmission of Wavelength-Division-Multiplexed Channels With Coherent Optical OFDM

Transmission performance for wavelength-division-multiplexed (WDM) systems with coherent optical orthogonal frequency-division multiplexing is simulated including the fiber nonlinearity effect. The simulation shows that the system Q of the WDM channels at 10 Gb/s is over 13.0 dB for a transmission up to 4800 km of standard single-mode fiber without dispersion compensation     

采用ASK调制的波分复用系统中滤波器带宽的优化设计

提出了采用幅移键控（ＡＳＫ）调制的波分复用（ＷＤＭ）系统中光滤波器带宽的优化设计问题。并根据对长距离波分复用系统中影响信噪比的主要因素的分析,计算了优化设计问题,数值计算给出了一些有意义的结果     

Hardware-in-the-loop simulator for research on fault tolerant control of electrohydraulic actuators in a flight control application

Testing fault tolerant control and diagnosis systems for hydraulic actuators under operating conditions that closely resemble the intended application is an important part of control system verification. This paper describes a hardware-in-the-loop (HIL) simulation framework that enables an experimental hydraulic actuator to be exercised as a flight control actuator against the numerical simulation of a high-performance jet aircraft. The HIL simulator is centered around a state-of-the-art hydraulic test bench that can experimentally simulate many of the common component faults in a servovalve driven actuator circuit. A second experimental hydraulic ram is used to create a wide range of in-flight operating conditions by replicating the aerodynamic load disturbance that is transmitted through the control surface hinge during flight maneuvers. The goal of the HIL simulator is to develop and objectively test novel fault tolerant control and diagnostics algorithms for fluid power actuators and to investigate, for the first time, the complex interaction between faulty flight actuator hardware and the overall aircraft performance. An overview of the HIL simulation architecture, which is executed on four networked desktop computers, is given and the hardware implementation is described. Issues related to the design of the force control system around the load emulator actuator are also discussed. The results of several HIL case studies, including a human-in-the-loop simulation, are presented to demonstrate the functionality of the HIL simulation environment.     

基于隐马尔可夫模型的切换飞行控制系统性能分析

该文研究了一种由电磁环境对电子设备产生的数字干扰来驱动的切换飞行控制系统性能分析模型。其中,从电磁干扰的产生原理角度,采用隐马尔可夫模型(Hidden Markov Model, HMM)描述数字电磁干扰特性并对其进行建模分析,同时针对HMM参数训练算法存在对初值选择敏感的问题,提出一种快速的初值选择策略,可以在经典Baum-Welch算法迭代下达到指定的收敛精度。最后将HMM电磁干扰注入分布式飞行控制系统性能观测平台,从理论与仿真的角度对比了不同电磁环境下分布式飞行控制系统的性能下降情况。仿真实验表明：与已有的数字电磁干扰建模分析方法相比,HMM具有更高的准确度,并且仿真所得性能下降程度与理论分析一致     

WDM coding for high-capacity lightwave systems

An interchannel parallel coding scheme in the wavelength domain-the WDM coding system-is proposed. The system differs from the usual serial coding systems and provides many advantages. First, data channels are completely unaltered in the coding process, rendering it very suitable for practical lightwave systems with standard bit rate. Second, parallel encoding/decoding systems are simpler than those of serial coding systems, being easier to be implemented in high-speed optical systems. Third, compared with serial coding, WDM coding is able to reduce heavily the number of encoding/decoding pairs. For example, a (15, 11) Hamming coded WDM system reduces the number from 12×11=132 to 1 at the line rate of STS-12. Fourth, the WDM coding system could offer infinite coding gain in dispersion-limited lightwave systems. Finally, WDM coding systems could correct single-channel burst error. The system performance was evaluated and the system limitation imposed by bit-skew among wavelength channels was analyzed. The results indicated that a 15-channel Hamming coded WDM system can reduce the uncoded BER from 10^-9 to 3×10^-17 and the distance limitation imposed by bit-skew is 250 km if a dispersion-shifted fiber is used and a channel span of 30 nm is assumed