光通信卷积码-误码测试系统设计及实验

设计并实现了卷积码-误码测试系统,以实验的方式研究了卷积码对光通信系统性能的改善作用,并完成了2.2km的无线光通信实验.实验结果表明,在无线光通信中,卷积码有良好的纠随机错误的能力,但对突发性错误的纠错能力较差.实验结果还表明,在传输速率低于100Mb/s时,由传输速率不同而引起的码间干扰的差别极其微弱.     

一种新型155Mb/s大气激光通信机的研制

介绍了一种新型155Mb/s大气激光通信机的设计和试验情况.该设备采用了非球面光学系统、大功率EDFA发射、ATP跟踪等先进技术,具有通信距离远、通信速率高、工作稳定等特点.     

34Mb/s和140Mb/s长中继间距光纤传输实验

无中继间距达250km的长距离光纤传输系统实验已经实现。本文将讨论这种系统设计方案的选择,接着叙述五种实验室的试验:全部用商用元件的176km34Mb/s色散限制试验,采用多模激光器和色散移位光纤,140Mb/s速率下超过220km和34Mb/s速率下超过233km的损耗限制的两个系统试验;在同样的线路速率下,进一步把距离分别延长到223km和251km的两个实验,其特点是采用了单一谱线DFB激光器和突变型单模光纤。     

一种用于大气激光通信透明传输的光端机

提出了一种解决大气激光通信中断问题的方案,详细介绍了该方案中光端机的设计.实验表明,该方案能有效实现大气激光通信中透明传输10Mb/s-160Mb/s的各种数据,并提高了大气激光通信系统的可通率.     

基于NRZ调制的40 Gbit/s无误码高速850 nm VCSEL设计与制备

850 nm的垂直腔面发射激光器（VCSEL）是短距离光互连的核心光源。随着对数据中心流量的需求增加，实现不归零（NRZ）调制高速无误码传输是目前的研究热点。本文设计制备了基于λ/2短腔和六层氧化限制层的高速850 nm VCSEL，室温下最高-3 dB带宽达到23.8 GHz。NRZ调制50 Gbit/s(1 m)和40 Gbit/s(100 m)速率下获得清晰的眼图。在未使用预加重、均衡和前向纠错的条件下，通过NRZ调制在1 m和100 m下无误码传输速率分别为40Gbit/s和30 Gbit/s。     

100 Mb/s聚合物光纤通信链路系统

报道了自行研制的聚合物光纤 10 0Mb s通信链路系统 ,并实现计算机之间多媒体信息传输。测试结果表明该系统传输速率达到 10 0Mb s·10 0m。     

一种新型的单光源双工通信系统

以单光源为基础光源,使用内调制与外调制相结合的调制方式,成功搭建了双工激光通信系统,并对其进行了理论分析与实验验证.光源部分作为中心基站(Central Station,CS),使用内调制实现下行链路,向基站(Base Station,BS)发送请求信息;BS端则使用声光外调制的方式实现上行反馈,向CS端发送反馈信息,实现了两个终端之间的相互通信.结果表明,该双工通信系统室内传输稳定,传输速率因器件而定,下行最高可达30 kb/s,上行最高可达3Mb/s,该通信系统可实现时分双工光通信,在相邻时段使用不同频率的光载波进行实时通信.     

天气因素对大气激光通信质量影响分析

利用一套新研制的155Mb/s 5km大气激光通信机做为测试样机,进行了长达一年多的外场实验,对设备在不同气象因素条件下的工作情况进行了详细分析和理论探讨,给出了晴、阴、雨、雾、霾、大风等各种天气条件下对光通信链路的影响结果及分析.     

12×2.5Gbit/s并行伪随机序列发生技术及在线误码块监测

利用FPGA产生并行高速伪随机序列和比特间插奇偶校验8位码误码块的方法实现了在线误码监测。建立了点到点并行高速光传输误码监测实验系统,该系统由12×2.5Gbit/s并行高速伪随机序列发生器、在线误码监测模块、12×2.5Gbit/s并行光接收模块和自制垂直激光阵列发射模块构成,并行光互联采用带宽为400MHz.km5米12芯62.5μm多模带状光纤。     

2Mb/s接口CRC帧性能分析

本文首先分析了2Mb/s数字接口信号原帧结构的性能,指出所存在的问题——误码监测能力低和不能有效地防止伪帧定位。然后介绍了2Mb/s CRC帧结构及CRC校验原理,分析了利用CRC识别伪帧定位和检测误码的能力,并使用马尔可夫链的方法得到误码漏检概率的计算公式和结果。     

140Mb/s混合集成光发射机

研制了一种混合集成140Mb/s单模半导体激光器发射机。该发射机由高速缓冲整形放大、LD驱动功能模块、LDAPC——LD自动功率控制功能模块、LDATC——LD自动温度控制功能模块,LD保护及寿命,信号终断告警功能模块和调顶功能模块所构成。发射机调制出纤光功率为-6dBm～-3dBm、消光比≤10％,在0～45℃范围内光功率变化在±1dB以内。该发射机和本所同时研制的混合集成光接收机配套,构成了目前140Mb/sPCM数字光端机的全新产品。     

Word timing recovery in direct detection optical PPM communicationsystems with avalanche photodiodes using a phase lock loop

A technique for word timing recovery in a direct detection optical pulse position modulation (PPM) communication system is described. It tracks on back-to-back pulse pairs in the received random PPM data sequences with the use of a phase locked loop. The experimental system consisted of an AlGaAs laser diode transmitter (λ=833 nm) and a silicon avalanche photodiode photodetector, and its used Q=4 PPM signaling at a source data rate of 25 Mb/s. The mathematical model developed to characterize system performance is shown to be in good agreement with the experimental measurements. Use of this recovered PPM word clock, along with a slot clock recovery system described previously, caused no measurable penalty in receiver sensitivity when compared to a receiver which used common transmitter/receiver clocks. The completely self-synchronized receiver was capable of acquiring and maintaining both slot and word synchronizations for input optical signal levels as low as 20 average detected photons per information bit. The receiver achieved a bit error probability of 10^-6 at less than 60 average detected photons per information bit     

Experimental characterization of integrated optical wireless components

Line of sight optical links can provide extremely high bandwidth communications between terminals, but in order to maintain alignment between transmitter and receiver, tracking is required. In this letter, we report results from a "solid-state" tracking transmitter and receiver. The transmitter consists of a custom complementary metal-oxide-semiconductor (CMOS) integrated circuit that is flip-chip bonded to a seven-element resonant cavity light-emitting diode. The receiver uses a custom seven-element InGaAs detector array that is flip-chip bonded to a CMOS integrated circuit. Results from an initial link demonstration show overall system operation at 100 Mb/s/channel, for Manchester coded data.     

A 107-pJ/bit 100-kb/s 0.18- $muhbox{m}$ Capacitive-Coupling Transceiver With Data Edge Signaling and DC Power-Free Pulse Detector for Printable Communication Sheet

A novel communication system which simultaneously achieves the mobility of wireless communication and the low-power performance of wireline communication is developed with a printable sheet. By combining meter-scale wireline communication and micrometer-scale wireless capacitive-coupling communication, the proposed communication system enables multiple electronic objects scattered over tables, walls, and ceilings to communicate contactlessly with each other by establishing communication paths without cumbersome physical connections. The transceiver developed for the 20 cm$times$ 20 cm communication sheet features a data-edge-signaling transmitter and a dc power-free pulse detector, thereby achieving the lowest energy of 107 pJ/bit at 100 kb/s in wireless communications at a distance of 60 cm in 0.18-$muhbox{m}$ CMOS.      

基于激光检测的无人机探测系统与实验

现有的无人机探测通常采用以雷达扫描为主,辅以其他传感器探测的方式。但是,目前使用雷达探测的成本较高,而激光器作为一种低成本、低功耗的器件已受到人们广泛关注。以激光为载体,结合无线光通信中的捕获、瞄准、跟踪(APT)系统,设计并实现了一种基于激光探测技术的无人机扫描定位系统,并以气球模拟无人机目标的测试方式,测试了该系统的定位精度和效率。扫描试验结果表明:在激光发射器平均功率小于40mW的情况下,该系统对目标的捕获定位能达到较高的精度,误差在5%以内,最大可探测范围为45m。     

二维大气无线光码分多址通信系统

在无线光通信系统中采用光码分多址(OCDMA)技术,可以充分利用其丰富带宽,提高系统性能。考虑背景光噪声、探测器噪声、多用户干扰和大气闪烁等影响因素,给出了二维无线光码分多址(2D-WOCDMA)系统模型,在该模型中采用了脉冲位置调制(PPM)和光纤布拉格光栅(FBG)编解码器。通过数值分析,详细讨论了该无线光通信系统的性能。结果表明,大气闪烁是影响二维无线光码分多址通信系统性能的重要因素,当其对数方差较大时,系统难以实现通信,需要采用诸如多用户检测、信道编码及阵列接收等技术提高系统的性能;二维无线光码分多址通信系统适合采用1550 nm波段;该通信系统还受背景光、雪崩光电二极管(APD)增益和调制消光比等因素的影响。     

自由光通信中PIN探测器光阈值特性研究

研究自由光通信中PIN探测器在1 064 nm波长下的阈值特性。为了观察PIN光电探测器的激光损伤阈值对光通信的影响,利用Nd:YAG激光器、衰减器、示波器和PIN探测器等仪器模拟无线空间光通信系统。实验以PIN探测器在1 064 nm波段为样本。通过调整衰减器的衰减系数,从而观察探测器达到强光饱和时通信波形的眼图变化,判断探测器是否能够继续通信。通过实验发现:探测器达到深度饱和时,系统通信出现脉宽展宽现象,并出现严重的码间串扰无法满足通信指标。通过实验阈值,建立空间数学模型。观察距离、束散角和辐照夹角对致盲激光器功率的影响。     

无线激光通信光发射模块的研究

为了提高现代武器系统在恶劣电磁环境中的通信和信息交换能力,充分利用激光的天然保密性,减少对无线电频率资源的占用,对无线激光通信系统中的光发射模块进行了设计。在信标光发射模块的设计中采用驱动电路与温度控制电路分离的设计方案;在信号光发射模块中采用掺银铒光纤放大器(EDFA)作为功率放大器的设计方案,并采用DS90LV001芯片完成PECL信号与LVDS信号转换。试验结果表明,信标光的最高输出功率为1.53 W,最高频率大于10 kHz;信号光的输出功率大于19.8 dBm,误码率低于10-7,消光比为10.2 dBm,完全满足设计需求。     

Slot clock recovery in optical PPM communication systems withavalanche photodiode photodetectors

Slot timing recovery in a direct-detection optical PPM communication system can be achieved by processing the photodetector output waveform with a nonlinear device whose output forms the input to a phase-locked loop. The choice of a simple transition detector as the nonlinearity is shown to give satisfactory synchronization performance. The RMS phase error of the recovered slot clock and the effect of slot timing jitter on the bit error probability were directly measured. The experimental system consisted of an AlGaAs laser diode (λ=834 nm) and a silicon avalanche photodiode photodetector. The system used Q =4 PPM signaling and operated at a source data rate of 25 Mb/s. The mathematical model developed to compute the RMS phase error of the recovered clock is shown to be in good agreement with results of actual measurements of phase errors. The use of the recovered slot clock in the receiver resulted in no significant degradation in receiver sensitivity compared to a system with perfect slot timing. The system achieved a bit error probability of 10^-6 at a received optical signal energy of 55 detected photons per information bit     

Wireless optical CDMA LAN: digital implementation analysis

In this paper we present and investigate a digital design and implementational details of a wireless optical CDMA (OCDMA) system based on generalized optical orthogonal codes (OOCs). A detailed digital implementation analysis and transmitter/receiver architectures in the context of the above design are fully studied. We analyze various subsystems for a wireless OCDMA system including detector and receiver structure, acquisition, and tracking blocks as well as evaluating their performance in a typical wireless OCDMA communication system. By analyzing two main parts of the system, namely, chip-level detector and OCDMA receiver blocks we evaluate the performance of the overall system. Analytical and simulation results are presented to depict system performance. Results on the design and implementation of such systems in this paper indicate the viability and the importance of OOC based wireless OCDMA technology to satisfy certain applications need in a wider communication system worldwide. Finally we describe an experimental prototype where we highlight the main aspects of the implementation of the system.