Semiconductor optical amplifier for wavelength conversion in subcarrier multiplexed systems

The fabrication and performance of a InGaAsP-InP semiconductor optical amplifier for wavelength conversion in subcarrier multiplexed system is described. The amplifier is of the buried facet design and has polarization and reflectivity gain ripple of less than 1 dB. Using subcarrier multiplexing, multiple 50-Mb/s data streams at a wavelength of 1.553 /spl mu/m are infected into the amplifier. The gain nonlinearity of the amplifier transfers the data to a different wavelength of light simultaneously injected into the amplifier. Error free retrieval of subcarrier multiplexed data has been demonstrated for the wavelength converted output. The small signal bandwidth of the wavelength conversion process is 5 GHz. Calculation suggests that higher bandwidth is feasible at higher input powers at the expense of lower modulation transfer during wavelength conversion.     

基于分布式光纤的网络化远程控制系统

随着光纤传感技术的发展,其逐渐呈现出网络化、并行监测与远程控制的发展趋势,为更好地利用光纤传感网络,设计基于分布式光纤的网络化远程控制系统。系统由使用层、存储层和服务层组成,包含分布式光纤传感器的服务层是系统的核心,其向存储层发送备案请求,将其中的光纤传感器地址存储在其中;使用层通过存储层获取可用地址列表,在其中任意控制一个或数个光纤传感器实施数据采集。使用层向服务层发送数据采集命令,服务层中嵌入式平台接收命令后传输至被控光纤传感器控制器执行采集命令,并将采集到的数据传输至FPGA内进行降噪、累计等处理,处理后的数据通过嵌入式平台反馈至使用层。实验结果显示,该系统控制下,光纤传感网络采集信息偏差低于5μrad,服务端响应时间提升25%以上,具有加高的噪声低抑制性能。     

Tuned optical receivers for microwave subcarrier multiplexedlightwave systems

An analysis of tuned optical-receiver noise performance for microwave subcarrier multiplexed lightwave systems is presented. The effect of correlation between the gate and the drain HEMT noise sources and the design of tuning networks to obtain partial noise cancellation were investigated. Anoptimization algorithm is used to determine the tuning elements values for minimizing noise of 16 dB for a 60-video-channel subcarrier multiplexing (SCM) system, and 12 dB for a 120-channel system, which allows a significant increase in passive optical network distribution capacity. Design results for tuned front-end receivers encompassing the effects of p-i-n, HEMT, and SCM band parameters are presented     

Crosstalk due to optical demultiplexing in subcarrier multiplexed systems

We report an in-depth investigation of the inter-modulation crosstalk in subcarrier multiplexing (SCM) systems with optical demultiplexing (ODeMux). Both theoretical derivations and numerical simulations show that the crosstalk in ODeMux systems mainly comes from the nonlinear mixing of the baseband and subcarrier modulations inside the signal channels. Several key parameters are then studied to estimate their effects on the magnitude of the crosstalk. As a result, performance optimization strategies are proposed for ODeMux SCM systems. In order to further enhance the transmission performance of ODeMux SCM systems, we discuss two techniques to suppress the inter-modulation crosstalk and analyze their effectiveness with numerical simulations.     

Optical interference in subcarrier multiplexed systems withmultiple optical carriers

It is shown that, when multiple optical carriers are used in a subcarrier multiplexing system, optical interference noise limits the system bandwidth or the number of available channels. Results of a statistical analysis are presented for a system with multilongitudinal mode semiconductor lasers. The results of the statistical calculations indicate that, when one channel per optical source is transmitted, then the system will be limited to only 16 video-quality channels. However, this number can be increased carefully by choosing and maintaining separate wavelengths for the lasers, in order to minimize the interference noise     

基于光纤的远程IO端口控制系统

介绍了一种基于光纤的远程IO端口控制系统,通过将光纤、以太网与嵌入式系统结合,采用VB6.0上位机软件实现远程通讯测试,提出了一种远程控制IO端口数据双向传输的解决方案。本系统以单片机MCF5223X系列芯片为主控模块的核心,从IO端口采集数据后由光纤传输至远端主机,远端主机通过VB6.0分析处理数据,使得远端主机与IO端口数据实时双向传输,实现远程控制IO端口的功能。本文给出了系统结构图和软件测试通讯图。     

基于子载波加权降低OFDM系统峰均功率比的方法

本文提出了一种通过对子载波数据进行加权来降低OFDM系统PAPR的方法.该方法实现简单,能有效降低OFDM系统的PAPR,且无需向接收端发送其它用于解调的信息.通过遗传算法求解每个OFDM符号的最优加权向量,在保证PAPR抑制效果的同时大大降低了加权系数的计算时间,并与投影拉格朗日法进行了比较.由于加权引起子载波功率的...     

Optical time domain reflectometry on optical amplifier systems

The use of optical time-domain reflectometry (OTDR) on long-span fiber transmission systems containing in-line optical amplifiers is discussed. Having identified the specific requirements for OTDR equipment, measurements were carried out on systems of up to 300 km in length, containing three semiconductor laser amplifiers. The results demonstrate that OTDR can be used not only for fault location on fiber links several hundred kilometers in length but also as an alternative to standard system supervisory techniques, thus providing the potential for minimizing the hardware in the optical amplifier stages of future long-span fiber optic transmission systems     

GSM在排水泵站远程监控系统中的应用

对于实时性要求不高的远程被控对象，目前可以应用基于PSTN(公共交换电话网)和基于GSM(移动通信网)的低成本远程监控系统来设计，对这二种方法进行了比较。详细介绍了基于GSM的低成本远程监控系统组成以及实现方法，已经成功应用在排水泵站远程监控中。     

60-channel FM video subcarrier multiplexed optical communication system

A subcarrier multiplexed (SCM) optical communication system is described which transmits 60 frequency-modulated (FM) video channels over 18 km of single-mode fibre with a 56 dB weighted signal/noise ratio.     

基于网络的远程实时监控系统的设计与实现

为了实现基于网络的远程实时监控系统,采用Java编写本地Web服务器,利用Dreamweaver设计监控页面,使得用户可在客户终端浏览实时监控系统网页,并通过此网页进行实时监控和查询历史记录。同时还给出了基于3G网络的实时监控系统和报警模块的设计思路。     

Microwave photonic filters based on optical semiconductor amplifier

Microwave photonic filters have been characterized by low loss,light weight,broad bandwidth,good tunability,and immunity to electromagnetic interference,and these filters can overcome inherent electronic limitations.Fiber-based filters are inherently compatible with fiber-optic microwave systems and can provide connectivity with built-in signal conditioning.This review paper presents developments of microwave photonic filters based on semiconductor optical amplifier in the last few years.Challenges in system implementation for practical application are also discussed.     

Microwave amplifier based RF optical receivers

Simple architectures for narrowband optical receivers are discussed. The proposed receivers are based on high-impedance photodiodes, lossless distributed matching circuits and matched impedance microwave amplifiers. The gain and noise properties of an experimental C-band receiver are reported.     

Low-cost adaptive directly modulated optical OFDM based on semiconductor optical amplifier

Low cost optical OFDM has great potential for next generation optical access networks and PONs, due to its high flexibility in bandwidth manipulation, and high spectral efficiency. Here, a low cost optical OFDM is proposed, based on adaptive direct modulation semiconductor optical amplifier. Adaptive current loading techniques for PAPR (peak to average power ratio) reduction are proposed and analyzed. Simulations show that the proposed adaptive techniques enable significant BER improvement.     

Margin measurements in optical amplifier system

The margin, or the difference between the received signal-to-noise (SNR) and the SNR required to maintain a given bit error ratio (BER), is important to the design and operation of optical amplifier transmission systems A new tehnique is described for estimating the SNR at the receiver's decision circuit when the BER is too low to be measured in a reasonable time. The SNR is determined from the behavior of the BER as a function of the decision threshold setting in the region where the BER is measurable. The authors obtain good agreement between the BER predicted using the measured SNR value and the actual measured BER     

Simulation of optical remote sensing systems

Research on understanding the remote-sensing process as a system and investigating the interrelated effects of various parameter is described. A system model for the simulation of remote-sensing systems is presented. The system is divided into three parts: the scene, the sensor, and the processing algorithms. Models are presented and implemented for these component systems. Validation of the system model is considered over a specific test site. Results of the simulation for various scene and sensor configurations are included. Results of applying the model to various system configurations using simulated Landsat sensors are then presented to show how the simulation can be used to investigate the interrelated effects of system parameters.<>     

一种基于MODEM的计算机远程监控系统

介绍一种通过公共电话交换网（PSTN）连接,用于供电系统的计算机远程监控系统。该系统由上位计算机、调制解调器、程控交换机和下位单片机系统组成。系统按分布式结构设计,可实现对多个太阳能供电站点的实时监控,应用于程控交换基站、无线通信基站供电系统的监控。结果证明系统具有操作方便、工作可靠、成本低廉等特点。     

基于原始套接字的局域网数据包监听系统

设计并实现了一个局域网数据包监听系统,能够将本局域网内所有的数据包截获并分析,对局域网内的数据传输进行实时监控,提高网络的安全性。从系统功能介绍、实现原理、软件设计等几个方面阐述了该系统的实现。     

一种基于MODEM的计算机远程监控系统

介绍一种通过公共电话交换网(PSTN)连接,用于供电系统的计算机远程监控系统.该系统由上位计算机、调制解调器、程控交换机和下位单片机系统组成.系统按分布式结构设计,可实现对多个太阳能供电站点的实时监控,应用于程控交换基站、无线通信基站供电系统的监控.结果证明系统具有操作方便、工作可靠、成本低廉等特点.     

Cycle slipping in an optical communication system employing subcarrier angle modulation

The output of an ideal photodetector that is modeled as a doubly stochastic Poisson process is used to excite a phase-locked loop. The rate of this Poisson process contains an angle-modulated subcarrier process that is modeled as a Gauss-Markov process. A measure transformation involving a martingale translation is applied to the suboptimal filter used to estimate the phase. Cycle slipping is then discussed with respect to the evolution of the phase error process under the new measure. The approach is in the context of a first-passage problem and uses a Kramers-Moyal expansion of the equation satisfied by the mean slip time. Various approximations to the jump rate and size are assumed, and a perturbation analysis results in asymptotic representations of the corresponding solutions. Comparisons with solutions obtained from so-called diffusion approximations are also included, as well as a specific example to illustrate the procedure.