基于遗传算法的倾斜式光接收机设计

光接收机作为室内可见光通信系统的重要组成部分,其接收角度的不同将会影响系统的性能。传统可见光通信系统采用的是垂直光接收机,其室内角落的信噪比(SNR)较低,信噪比峰-谷值较大。为了降低SNR峰-谷值,提高SNR在室内分布的均匀性,本文提出并设计了基于遗传算法的倾斜式光接收机。数值分析结果表明,采用倾斜式接收机的可见光通信系统,SNR的分布更加均匀。在12 W单个LED光源的系统中,SNR的峰-谷值改善了4.98 d B。在总功率为12 W的四个LED光源的系统中,SNR的峰-谷值改善了2.51 d B。由此可见,在可见光通信系统中,采用倾斜式光接收机可以改善系统的性能。     

可见光通信系统光源优化布局模型

针对可见光通信系统存在的光照度和接收平面功率分配不均匀的问题,提出了基于多种群遗传算法的光源布局模型。以15个LED灯为例,构造和接收功率方差有关的适应度函数,采用多个种群协同进化的方式,对LED灯的位置坐标信息进行寻优。经Matlab R2016a仿真结果表明,优化后的功率分布直观上更均匀,功率方差达到1.5744 dBm,照度范围为889 lx ~1009 lx,照度均匀度亦达到91.73%,均优于传统遗传算法优化的布局和多种群遗传算法优化的矩形布局,从而为系统优化LED灯布局使得用户获得更好的通信体验提供了一种借鉴方案。     

一种兼顾照明与通信的环形光源布局模型

传统基于阵列的光源布局方式在室内难免存在光照度及系统误码率不均匀现象,为提高系统照度均匀性及通信可靠性,需合理对光源进行优化布局。本文以4 m×4 m×3 m的房间为模型,设计了单LED阵列+灯带的环形光源布局模型。模型中间采用6×6 LED阵列,阵列内部灯珠之间的距离为0.3 m;四周采用环形灯带形式,灯珠个数为316个,灯珠之间的距离为0.05 m。仿真结果表明,该模式下系统光照度均值为437.08 lx,光照度均匀性为93.9%,同时,系统误码率均值为2.8716×10-7。因此,本文所设计的环形光源布局模型兼顾了室内光照度分布的均匀性和通信的可靠性,可同时满足室内照明和通信,为室内可见光通信光源布局提供了一种优化方法。     

空间光通信系统的设计及实现

提出一种较全面的空间光通信系统结构。该系统的光发射接收子系统采用三发三收的设计方法,以增大光的发射功率和接收功率;APT子系统采用望远镜进行粗瞄准,音频调制光标信号进行精瞄准;控制子系统采用Ethernet接口,远程通过Internet对系统进行测量和控制的设计方法。给出一个近地大气空间光通信系统的设计实例, 其信号传输速率为155Mbps,传输距离为4km,在误码率不大于10-9条件下,系统接收灵敏度达到-52dBm。     

室内可见光通信系统的硬件平台开发

当今室内可见光通信系统技术是国内外光无线通信领域的研究热点之一，考虑到当前主要还集中在理论分析和建模仿真阶段，本文将LED照明技术与室内可见光通信技术相结合，构建了室内可见光通信系统的整体架构。从通信速度、抗干扰能力、驱动能力和信号接受能力等方面综合考虑完成了整个系统的硬件方面开发，在满足误码率的条件下支持最高通信速度可达2Mb／s。     

JJG1035—2008《通信用光谱分析仪》检定规程解读

随着光通信科学及光通信产业的不断创新和发展,各种光谱分析类仪器的应用越来越广泛,光谱分析仪的检定和测量也渐为计量检定人员所重视。例如,密集波分复用（DWDM）是当前光通信系统的主流技术,也是实现下一代高速率、大容量光通信网络的基础之一,而光谱分析仪则是测试DWDM系统的重要设备之一。通信用光谱分析仪是用来测量光信号光谱功率分布的计量器具,不仅可以测量光源等有源器件的光谱功率分布,也可测量一些无源器件的光谱传输特性,满足光通信生产和应用领域最广泛的测试需求。     

用于超导扭摆磁铁同步辐射光热负载的吸收器

６Ｔ超导扭摆磁铁的同步辐射光是合肥光源储存环超高真空系统中的强热源。在超高真空室内设置铜吸收器，避免了Ｗｉｇｇｌｅｒ同步辐射光直接照射不锈钢真空室壁。本文描述了热源的功率分布，吸收器上的热负载通量以及吸收器表面的温度分布。     

光纤耦合效率与接收光强计算研究

由于用近似方法计算出的光纤耦合效率和接收光功率与实验测量之间存在差异,有必要探讨更准确的计算方法以满足应用的需要。通过对径向变量的积分,导出了在高斯光强分布下对接收光纤端面进行面积分计算的一元积分式,从而可以快速准确地对光纤的耦合效率和接收光功率进行数值计算。对62.5/125多模光纤的耦合效率和接收光功率进行的数值计算和实验测量说明,光纤的耦合效率只有用准确的数值计算才能给出与实际相符合的计算结果。使用芯径较大的接收光纤测量出射光束的近场光强分布时,光纤接收光强分布较光束的光强分布有较大的展宽,其相对误差甚至可达60%。     

空间相干光通信外差效率及天线像差的影响

空间相干光通信中接收天线像差会使光外差效率下降.对本振光为高斯分布,信号光为爱里斑分布的光外差效率进行了研究,给出了无像差时外差效率的解析表达式.当焦平面上爱里斑半径与本振高斯光束光腰半径之比为1.71时,有最大外差效率81.45%.然后以本振光为理想的高斯光束,信号光受像差的影响,研究了倾斜、离焦、球差、彗差、像散等像差引起的光外差效率损失,给出了存在像差时外差效率的一维积分表达式.研究表明即使在采用离焦校正后,一个波长的球差引起的附加外差效率损失仍可达0.9 dB.因此对于爱里斑位于光轴上的接收天线,在设计时需仔细处理球差的影响.     

光通信历史与发展研究综述

当今通信领域,光通信已经成为广泛使用而又具有巨大发展空间的一类通信科学,就光通信发展历程分为光纤、光源、光纤通信系统三方面进行回顾与介绍,并对光通信的发展趋势作简要的展望.     

Evolutionary algorithm based uniform received power and illumination rendering for indoor visible light communication

In this paper, an evolutionary algorithm based optimization scheme is proposed to realize uniform received power and illumination distribution on the communication floor for fully diffuse indoor visible light communication. Simulation results show that in three distributed lighting configurations, by dynamically modifying the relative optical intensity of transmitters the dynamic range of the received power, referenced against the peak received power, can be reduced to about 40.0% while the uniformity illuminance ratio can be improved up to about 0.70 with the impact to the root mean square delay spread and bandwidth being negligible. Furthermore, the relationship between the field of view of the receivers and the optimization performance is presented as well.     

Natural light illumination system

In recent years, green energy has undergone a lot of development and has been the subject of many applications. Many research studies have focused on illumination with sunlight as a means of saving energy and creating healthy lighting. Natural light illumination systems have collecting, transmitting, and lighting elements. Today, most daylight collectors use dynamic concentrators; these include Sun tracking systems. However, this design is too expensive to be cost effective. To create a low-cost collector that can be easily installed on a large building, we have designed a static concentrator, which is prismatic and cascadable, to collect sunlight for indoor illumination. The transmission component uses a large number of optical fibers. Because optical fibers are expensive, this means that most of the cost for the system will be related to transmission. In this paper, we also use a prismatic structure to design an optical coupler for coupling n to 1. With the n-to-1 coupler, the number of optical fibers necessary can be greatly reduced. Although this new natural light illumination system can effectively guide collected sunlight and send it to the basement or to other indoor places for healthy lighting, previously there has been no way to manage the collected sunlight when lighting was not desired. To solve this problem, we have designed an optical switch and a beam splitter to control and separate the transmitted light. When replacing traditional sources, the lighting should have similar characteristics, such as intensity distribution and geometric parameters, to those of traditional artificial sources. We have designed, simulated, and optimized an illumination lightpipe with a dot pattern to redistribute the collected sunlight from the natural light illumination system such that it equals the qualities of a traditional lighting system. We also provide an active lighting module that provides lighting from the natural light illumination system or LED auxiliary sources, depending on circumstances. The system is controlled by a light detector. We used optical simulation tools to design and simulate the efficiency of the active module. Finally, we used the natural light illumination system to provide natural illumination for a traffic tunnel. This system will provide a great number of benefits for the people who use it.     

Simple Mathematical Models for Temporal,Spatial, Angular,and Attenuation Characteristics of Light Propagating Through the Atmosphere for Space Optical Communication:

Abstract

Mathematical models are developed to characterize propagation through a turbid medium at three different wavelengths in the visible and near infrared spectral range. These models are based upon relations between the temporal, angular, and spatial spread of electromagnetic unpolarized radiation, geometrical path length, particle size distribution, and the medium's propagation parameters such as Mie scattering, and absorption coefficients, Mie phase-function, and optical thickness. Calculations of the radiation characteristics were carried out using Monte Carlo simulations. Here, atmospheric particulates are used to model turbid media for optical thickness between 1 and 6, emphasizing optical communication applications, The advantage of this work is the ability to predict simply and in real time important radiation parameters relevant to any optical communication system. Results indicate very high correlation between optical thickness and propagation characteristics. For transmission, comparison is made to Bucher's model. Results are similar except for absorption effects which are not included in Bucher's model. Some important conclusions are derived such as the prediction that it is advantageous to use longer wavelength radiation through the atmosphere. In addition, there is a very dominant back scattering effect, involving up to 50% of transmitted power for optical densities as low as 6. On the other hand, power density of received scattered light is very low for conventional distances relevant to satellite optical communication, and can be neglected. On the basis of simulation results, the received radiation is of unscattered light only for any optical communication application. The dominant mechanism relating to radiation attenuation is scattering rather than absorption.     

大视场可见光目标模拟器光学系统设计

具有特定视场的动态可见光目标模拟器是可见光成像系统测试与评估的关键设备,该模拟器的准直投影光学系统决定了基于数字微镜阵列(DMD)的动态景象投射器的性能。根据成像系统测试与评估需求,本文对可见光准直投影光学系统进行设计。基于对投影光学系统的参数计算,设计了视场58°的大视场可见光目标模拟器光学系统。将设计结果与成像光学系统进行匹配仿真,获得了良好的配合效果。通过对所研制的系统进行测试,实验结果表明所设计的光学系统完全满足模拟器的要求和对动态场景的仿真需求。     

预编码室内MIMO可见光通信系统空间相关性分析

为了解决多用户MIMO(MU-MIMO)室内可见光通信中存在用户间干扰问题及对角化(BD)算法所产生的子信道强弱的问题,利用子流选择BD算法,对室内MU-MIMO可见光通信系统的误码率进行优化。建立了MU-MIMO室内可见光通信的信道模型,利用控制变量法并采用不同LED与PD距离的参数,对比了在4×4 MIMO与8×8 MIMO两种不同的室内系统布局方式下的信道空间相关性,分析对比子流选择BD算法及BD算法的系统容量及误码率性能。结果表明,随着空间相关的不断增强,误码率性能下降,子流选择BD算法相对于BD算法可以带来4 dB以上的增益。     

Demonstration of a White Laser with V2C MXene‐Based Quantum Dots

Multicolor photoluminescence over the full visible color spectrum is critical in many modern science and techniques, such as full‐color lighting, displays, biological and chemical monitoring, multiband communication, etc., but the ultimate white lasing especially on the nanoscale is still a challenge due to its exacting requirements in the balance of the gain and optical feedback at different wavelengths. Recently, 2D transition metal carbides (MXenes) have emerged, with some superior chemical, physical, and environmental properties distinguishing them from traditional 2D materials. Here, a white laser with V₂C MXene quantum dots (MQDs) is originally demonstrated by constructing a broadband nonlinear random scattering system with enhanced gain. The excitation‐dependent photoluminescence of V₂C MQDs is enhanced by passivation and characterized, and their localized nonlinear random scattering is realized by the generation of excitation‐power‐dependent solvent bubbles. With the optimized excitation, the blue, green, yellow, and red light is amplified and simultaneously lased. This work not only provides a kind of promising material for white lasers, but also a design strategy of novel photonics for further applications.     

Flexible Visible‐Light Photodetectors with Broad Photoresponse Based on ZrS3 Nanobelt Films

Two new flexible visible‐light photodetectors based on ZrS₃ nanobelts films are fabricated on a polypropylene (PP) film and printing paper, respectively, by an adhesive‐tape transfer method, and their light‐induced electric properties are investigated in detail. The devices demonstrate a remarkable response to 405 to 780 nm light, a photocurrent that depends on the optical power and light wavelength, and an excellent photoswitching effect and stability. This implies that ZrS₃ nanobelts are prospective candidates for high‐performance nanoscale optoelectronic devices that may be practically applied in photodetection of visible to near infrared light. The facile fabrication method is extendable to flexible nanodevices with different nanostructures.     

可见光通信中LED非线性补偿和带宽拓展技术

可见光通信(VLC)是一项有前景的技术,作为现有无线通信网络的有益补充,可提供高速率、低延迟及多设备接入等通信服务。借助传统无线通信的高性能编码调制技术,已经设计并实现了各种适配于VLC系统的物理层通信技术。不同于传统射频通信,VLC采用LED作为信号的发射源,LED的调制容易产生非线性失真且调制带宽有限,已成为VLC高速通信的技术瓶颈。针对这两方面的挑战,本文以白光LED为出发点,阐述了白光LED能有效兼顾照明和通信的特性,总结和分类了非线性失真补偿和拓展调制带宽的多种技术,最后本文提出了LED封装材料及工艺、新型Micro-LED器件研究、光源布局设计、码间干扰消除技术等开放性研究问题,以期提高可见光通信系统的性能。