Optical Techniques for Information Security

This paper presents an overview of the potential of free space optical technology in information security, encryption, and authentication. Optical waveform posses many degrees of freedom such as amplitude, phase, polarization, spectral content, and multiplexing which can be combined in different ways to make the information encoding more secure. This paper reviews optical techniques for encryption and security of two-dimensional and three-dimensional data. Interferometric methods are used to record and retrieve data by either optical or digital holography for security applications. Digital holograms are widely used in recording and processing three dimensional data, and are attractive for securing three dimensional data. Also, we review optical authentication techniques applied to ID tags with visible and near infrared imaging. A variety of images and signatures, including biometrics, random codes, and primary images can be combined in an optical ID tag for security and authentication.      

Optoelectronic parallel processing with surface-emitting lasers andfree-space interconnects

Parallel optoelectronic processing that uses smart pixel arrays and free space interconnections may provide an attractive alternative to applications that exhibit a large degree of functional parallelism and require massive input/output data rates. Two fine-grain parallel architectures based on two-dimensional arrays of processing elements are discussed in this paper. The logic complexity of the smart pixels ranges from two-input AND and XOR gates for a database filter to multiple-input multiple-output compare-and-exchange modules for a recirculating bitonic sorting unit. Both systems use vertical-cavity surface-emitting lasers as light sources but light detection and logic are implemented differently. The data filter uses GaAs-based phototransistors while the sorting unit requires silicon detectors and CMOS circuitry for its more complex logic. The free-space one-to-one interconnection patterns required between processing planes can be realized with either refractive or diffractive optics and their simplicity and regularity permit easy scale-up     

Technology for the 1990s

A forecast of the practical and promising devices, circuits, and systems that can be expected in the next one to five years is presented. It is based on a survey of a group of distinguished practitioners throughout the industry. The forecasts cover the areas of lasers and electrooptics, integrated optoelectronics, electron devices, digital integrated circuits, high-frequency and microwave devices, VLSI signal and image processing systems, analog ICs and signal processing, power electronics and systems, neural systems and applications, and medical image and signal processing. A particularly optimistic outlook is seen for lasers, fiber optics, optoelectronic ICs, and optical switching and processing. Digital ICs and power electronics are also expected to make steady gains. In addition, flat panel displays will attract a fair amount of activity, with the liquid-crystal and electroluminescent types emerging as the leaders in this decade. Looking further out, advances in artificial and biological neural systems represents a natural extension to more sophisticated problem-solving in speech processing, vision and communications     

基于轨道角动量的自由空间光通信研究与进展

利用光的轨道角动量传递信息可有效提高信息传输的速率。介绍了光轨道角动量的基本概念和主要特性,探讨了基于轨道角动量的自由空间光通信的基本原理和典型系统,并对相关的关键技术进行了分析,在此基础上,对基于轨道角动量的自由空间光通信的应用前景和发展趋势作了展望。     

一种在离焦情况下获得高分辨率图像的新技术

在遥感、军事侦察和医疗成象等领域,需要得到目标的高分辨率图像．而像面离焦直接影响了成像质量、降低了空间分辨率．为了得到高分辨率图像,往往采用自动焦面补偿装置或温控系统来克服离焦现象,但这又不利于仪器的小型化和轻量化．本文提出,在光学系统光路中加入一特殊设计的非球面掩模板,并对经过位相掩模板后的图像进行图象处理得到清晰图像．使光学系统在大离焦量的情况下仍可获取高分辨率的图像．这对于光学遥感器在复杂的空间环境中获取高分辨率图像具有十分重要的意义。     

Signal processing for optical communication

Optical communication plays a significant and increasing role in our society. The public demand for higher network speed requires an optical backbone network with larger capacity. Accompanying high transmission-rate optical communications system are severe technical specifications for optical devices and systems. Many popular optical devices could be represented with a digital filter model as described in this article. Use of well-developed signal processing techniques and algorithms to design these optical devices is a wise use of existing technology. The wavelength division multiplexing (WDM) system, which is the dominating optical communication system, is introduced in this article. Three signal processing application examples for optical communications are presented: optical wavelength interleaver, an all-pass filter for chromatic dispersion compensation, and an electronic equalizer. As demonstrated in this article, signal processing could play an important role in the development of advanced optical communication systems. However, as demonstrated in the case of an electronic equalizer, some optical system characteristics may require special attention if signal processing techniques are to be applied successfully. Therefore, interdisciplinary cooperation between researchers in optics and signal processing will be crucial for optical communications to fully benefit from signal processing.     

Evaluation of light beams for short and medium range wireless communications

Technological improvements in free space optical communication systems have reduced the cost and alternatives to fiber optic transmission. The advantages of the free space optical link over fiber optic cabling are primarily economic. In line with the demand for gigabyte link from 10 Mbit/s to 10 Gbit/s in the market, the uses of free space optical communication systems have increased exponentially from 1995 to 2008. However, free space optics is subject to atmospheric effects such as attenuation and scintillation which can reduce link availability and may introduce errors not seen in fiber transmission. In this paper we argue that optical wireless communication is an alternative to fiber optic transmission in short and medium range wireless communications and we discuss that the liability and availability of the free space optical link is mainly determined by the local atmospheric condition, this is to say that the transmission quality may be affected by weather conditions. For the evaluation we constructed an experimental communication network with a free space system. One way to characterize the strength of the turbulence fluctuation is by examining the Rytov variance for a plane wave. This Rytov variance physically represents the intensity fluctuation induced by atmospheric turbulence.     

基于自适应光学技术的高速流场效应模拟方法

在高分辨率天文观测和空间测绘过程中,高速流场效应会造成目标光学波前畸变,影响探测器分辨率。从高速流场造成的光学效应对空间观测的影响入手,研究分析了自适应光学技术及其关键器件-光学变形镜的技术特点,提出了一种基于光波波面调制技术和光程差（OPD）数据的高速流场光学传输效应模拟方法,并完成了初步验证实验。其中,通过光线追迹法和物理光学方法计算高速流场光学传输效应而获得的体现目标光束波面畸变程度的光程差（OPD）数据,该数据用于光学变形镜的控制驱动。这种模拟方法可用于空间对地观测过程中流场环境造成的透射光斑抖动、偏移等光学波面畸变效应仿真,实现在实验室环境下对光学传感器性能和空间光学探测系统高速流场效应半实物仿真和高速流场扰动校正能力的测试评估。     

自由空间微光学元件的研制

介绍了一种新近产生的被称为自由空间微光学平台（ Ｆ Ｓ Ｍ Ｏ Ｂ）的三维空间集成光学系统。并提出了一种用二氧化硅（ Ｓｉ Ｏ２）作光学材料、光刻胶和溅射铜（ Ｃｕ）薄膜作牺牲层、电镀铁镍（ Ｆｅ Ｎｉ）作支撑结构的制作自由空间微光学元件的新工艺。研制成功了多种与基底相垂直的三维位相型微光学元件。     

Optical parallel logic gates using a shadow-casting system for optical digital computing

A new, simple method of optically implementing optical parallel logic gates has been described. Optical parallel logic gates can be implemented by using a lensless shadow-casting system with a light-emitting diode (LED) array as a light source. Pattern logic, i.e., parallel logic for two binary patterns (variables), is simply obtained with these gates; this logic describes a complete set of logical operations on a large array of binary variables in parallel. Coding methods for input images are considered. Applications of the method for a parallel shift operation and optical digital image processing, processing of gray-level images, and parallel operations of addition and subtraction for two binary variables are presented. Comparison of the operation of the proposed optical logic gate with that of array logic in digital electronics leads to a design concept for an optical parallel array logic system available for optical parallel digital computing.     

Optical computing advances logically for image processing

A powerful application of optical computation, digital optical cellular image processing (DOCIP), is discussed. DOCIP uses digital optical computing techniques to perform cellular logic operations or extended array functions on images. Cellular logic is reviewed, and a binary image algebra (BlA) that serves as an analysis and synthesis tool for cellular image processing systems is described. Some DOCIP architectures that have been proposed or experimentally demonstrated are discussed and classified as image-algebra-type processors or symbolic-substitution-type processors. The optical and optoelectronic implementations of these architectures are also discussed     

计算光学成像:何来，何处，何去，何从？

计算光学成像是一种通过联合优化光学系统和信号处理以实现特定成像功能与特性的新兴研究领域。它并不是光学成像和数字图像处理的简单补充,而是前端（物理域）的光学调控与后端（数字域）信息处理的有机结合,通过对照明、成像系统进行光学编码与数学建模,以计算重构的方式获取图像与信息。这种新型的成像方式将有望突破传统光学成像技术对光学系统以及探测器制造工艺、工作条件、功耗成本等因素的限制,使其在功能（相位、光谱、偏振、光场、相干度、折射率、三维形貌、景深延拓,模糊复原,数字重聚焦,改变观测视角）、性能（空间分辨、时间分辨、光谱分辨、信息维度与探测灵敏度）、可靠性、可维护性等方面获得显著提高。现阶段,计算光学成像已发展为一门集几何光学、信息光学、计算光学、现代信号处理等理论于一体的新兴交叉技术研究领域,成为光学成像领域的国际研究重点和热点,代表了先进光学成像技术的未来发展方向。国内外众多高校与科研院所投身其中,使该领域全面进入了“百花齐放,百家争鸣”的繁荣发展局面。作为本期《红外与激光工程》——南京理工大学专刊“计算光学成像技术”专栏的首篇论文,本文概括性地综述了计算光学成像领域的历史沿革、发展现状、并展望其未来发展方向与所依赖的核心赋能技术,以求抛砖引玉。     

Radio-over-Fibre access for sustainable Digital Cities

Pervasive broadband access will transform cities to the net social, environmental and economic benefit of the e-City dweller as did the introduction of utility and transport network infrastructures. Yet without action, the quantity of greenhouse gas emissions attributable to the increasing energy consumption of access networks will become a serious threat to the environment. This paper introduces the vision of a ‘sustainable Digital City’ and then considers strategies to overcome economic and technical hurdles faced by engineers responsible for developing the information and communications technology (ICT) network infrastructure of a Digital City. In particular, ICT energy consumption, already an issue from an operating cost perspective, is responsible for 3 % of global energy consumption and is growing unsustainably. A grand challenge is to conceive of networks, systems and devices that together can cap wireless network energy consumption whilst accommodating growth in the number of subscribers and the bandwidth of services. This paper provides some first research directions to tackle this grand challenge. A distributed antenna system with radio frequency (RF) transport over an optical fibre (or optical wireless in benign environments) distribution network is identified as best suited to wireless access in cluttered urban environments expected in a Digital City from an energy consumption perspective. This is a similar architecture to Radio-over-Fibre which, for decades, has been synonymous with RF transport over analogue intensity-modulated direct detection optical links. However, it is suggested herein that digital coherent optical transport of RF holds greater promise than the orthodox approach. The composition of the wireless and optical channels is then linear, which eases the digital signal processing tasks and permits robust wireless protocols to be used end-to-end natively which offers gains in terms of capacity and energy efficiency. The arguments are supported by simulation studies of distributed antenna systems and digital coherent Radio-over-Fibre links.     

Digital optical computing

This paper concerns binary digital computing systems in which the information-carrying medium consists entirely or primarily of photons. The paper begins with a review of analog, discrete, and binary methods of representing information in a computer, followed by a survey of many techniques for implementing binary combinatorial and sequential logic functions with individual optical devices and arrays of devices. Next is a discussion of communication, interconnection, and input-output problems of digital electronic and optical computers at the gate, chip, and processor level. A particular architecture for implementing general sequential optical logic systems including digital optical processors is described. This architecture avoids some of the interconnection problems of electronic integrated circuits and VLSI systems, and offers the potential of non von Neumann parallel digital processors. Finally, the current limitations and future needs of optical logic devices and digital optical computing systems are outlined.     

同轴偏视场共孔径面阵成像光学系统设计

随着对空间信息获取能力的要求不断提高,使得高分辨率动态遥感成为空间光学领域一个新的研究热点。偏视场同轴三反光学系统具有长焦距、体积小、轻量化程度和成像质量高等特点,能够满足低轨视频卫星高分辨率、多谱段、多功能性和低成本的要求,因此在高分辨率动态遥感领域有着广泛的应用前景。以高斯光学和三反射消像差理论为基础,设计了可见光面阵成像、近红外和中红外线阵推扫成像的共孔径光学系统。可见光系统焦距4.1 m,近红外系统焦距2.6 m,中红外系统焦距1.85 m,三者孔径均为520 mm,视场均为0.60.6,成像质均接近衍射极限,成像质量良好。系统总长小于f'visible/3.7,且系统的加工和装配公差较为宽松,易于实现。     

自由空间光通信系统

自由空间光通信(FSO)是一个通过自由空间(大气)传输高速率光信号的技术,自由空间光通信系统的特点是高带宽、低成本、易安装、保密性好、无须频率申请、传输协议透明。这篇文章详细叙述了FSO系统的整体电路设计和控制程序设计。     

一种新的自适应增益盲优化算法提高自由空间光通信性能

由于大气湍流的影响,光束在大气中传输时产生 严重畸变,造成自由空间光(FSO)通信链路 性能恶化。为了提高系 统性能,构建了基于盲优化自适应光学的FSO通信系统,提出了一种新的自适应 增益随机并行梯度下降(SPGD)优化 算法。数值模拟结果表明,本文算法对大气湍流引起的波前误差进行实时补偿,能 够达到 很好的校正效果,比固定增益优化算法具有更好的收敛速度和精度。     

Advanced digital receiver principles and technologies for PCS

The synergy between digital radio communications and VLSI signal processing is revolutionizing the design of wireless terminals. Driving this synergy are certain fundamental paradigms in modern communication theory, digital signal processing, and VLSI design. The authors discuss the modern centers-of-gravity model, which they believe is emerging as the basis for the successful design and implementation of advanced digital communication systems. Central to this model are design principles that enable engineers to systematically derive digital receiver structures and explore algorithm and architecture trade-offs using sophisticated tools. Digital signal processing technology is critical in the implementation of these digital receiver structures efficiently. Finally, CAD tools for digital communications system design and design space exploration are shown to be of crucial importance in the efficient execution of these designs     

可编程光纤传输实验系统的设计

设计了一套以光收发模块为核心的数字信号光纤传输实验系统.数字信号处理部分选用了复杂可编程逻辑器件EPM7128SLC84-15,通过拨码开关可以产生伪随机序列并作为输入信号进入EPM7128输入端,对其进行任意编码后,信号进入光纤传输.接收端再进行解码处理,并用LED或示波器显示结果.实验系统工作可靠稳定,其不仅可用于数字信号光纤传输实验教学,而且在较短距离、较大容量的局域网信号传输中具有实用价值.     

Hardware implementation of a novel water marking algorithm based on phase congruency and singular value decomposition technique

The effortless accessibility of digital information and the simplicity of the digital systems have left the contents over the digital media extremely insecure. Digital watermark based information hiding is a prospective means for copyright protection, authentication, integrity verification and intellectual property right protection. Phase congruency technique works on the principle that perceptually significant image features have effect at spatial locations, where the essential Fourier components are maximally in phase with one another. An adaptive digital watermarking algorithm for better performance in multi-parametric solution space is developed here for hiding the copyright information by means of phase congruency and singular value decomposition supported information hiding technique. Performance evaluation of the algorithm is performed using simulation in Matlab in terms of Peak Signal to Noise Ratio, Structural Similarity Index Metrics, and Normalized Cross correlation index. Hardware realization up to the register transfer logic schematic level has been performed using high performance field programmable gate array board. The device utilization is 26% only, the dynamic power consumption of the circuit is 5.029 mW and delay after clock is 1.539 ns only. The experimental analysis establishes better robustness of the proposed algorithm as it stands against various attacks along with better data hiding capacity.