Optical implementation of heteroassociative loop

Optical implementation of heteroassociative loop based on an imaging system using liquid crystal devices as spatial light madulators is reported. Experimental operations with 7×7-pixel patterns are demonstrated.     

Optical coding scheme for all-optical analog-to-digital conversion using asymmetrical Y-branch waveguide

The novel optical coding scheme for all-optical analog-to-digital conversion has been proposed, in which asymmetrical Y-branch waveguide structures have been introduced to achieve the desired optical power splitting. The optical performance has been simulated by using finite-difference beam propagation method (FD-BPM), which shows that the designed component exhibits good coding performance. Experimentally, the optical coding component has been fabricated and measured. The optical power contrast between bit code 1 and 0 at output port is more than 37 dB, and measured imbalance of output power is less than 1.5 dB for bit code 1.     

Optical arithmetic unit using bit-WDM

A novel arithmetic unit is proposed consisting of a pipelined optical ripple carry adder that adds two words with bits multiplexed by different wavelengths on a single fiber. The addition result is returned to a fiber bus in the same format as the incoming words. The corresponding operand bit pairs are split off the fiber using wavelength division demultiplexers. Full adders compute the sum for each bit pair and the carry from the next lower significant bit pair. The full adder uses couplers and NOT, NOR and novel XOR logic gates constructed using semiconductor optical amplifiers for gain and wavelength shifting.     

Multiple-valued logic unit design using polarization-encoded optical shadow-casting

An efficient technique for the design of multiple-valued logic circuits using polarization-encoded optical shadow-casting is presented. As an illustration, a trinary full subtracter is designed using this technique. The resulting logic unit is compared with those obtained by using other algorithms.     

Optical implementation of an efficient modified signed-digit trinary addition

Efficient parallel schemes for carry-propagation-free addition of modified signed-digit trinary numbers are presented. The necessary minterms for implementation using an optical programmable logic array area are derived. The proposed schemes require only a truth table of 25 entries compared with an earlier scheme of 625 entries. The proposed schemes are amenable to optical implementation. Experimental results using an optical programmable logic array are demonstrated. The experiments show the problems of noise and crosstalk. This suggests some dc bias is necessary to increase the signal-to-noise ratio of the optical circuit.     

Polarization-encoded optical shadow casting: an efficient multiprocessor design using truth-table partitioning

An efficient multiprocessor has been designed using a polarization-encoded optical shadow casting truth table partitioning scheme. As an example, the design algorithm for identifying the source patterns, input patterns, and output mask for the design of an adder-subtracter is presented.     

用于图像高压缩比编码的方向滤波器的光学实现

本文针对光学与数字技术结合的实现图像高压缩比编码的一种方案——方向滤波方法提出利用补偿滤波技术来保持图像边缘信息,从而利用光学滤波技术实现数字滤波运算,给出高达30:1的高压缩比编码结果.     

Optical sorting using an array of optical vortices with fractional topological charge

An array of optical vortices with fractional topological charge is generated using a phase-only Talbot array illuminator and used to sort microparticles. Our theoretical analysis and experimental results reveal that when a particle passes through a fractional vortex array, it will be driven by two forces, intensity-gradient force and phase-gradient force, and the cooperation of these two forces can improve its ability in optical sorting because of the special intensity and phase distribution of the fractional optical vortex array. Larger angle separation could be obtained with moderate laser power.     

Optical implementation of perfect shuffle using Billet lens

This paper presents an optical system to implement perfect shuffle network us-ing Billet lens.Optical perfect shuffle network of high density and large capacity can be real-ized in this system with higher optical efficiency.     

Optical panel with full multitouch using patterned indium tin oxide

This study proposes an optical panel with full multitouch using the patterned indium tin oxide (ITO) and an algorithm matrix to avoid ghost points. The patterned ITOs include the virtual high and low impedances. The algorithm matrix with two configurations of equivalent circuits for array scanning is derived using the voltage divider rule. The fabrication process of the multitouch panel is carried out using microelectromechanical systems technology. The optical characteristics of the multitouch panel in the UV, visible, and IR regions are measured using photometric analysis. The multitouch panel, containing sensing pixels of 30×30 arrays, has a pixel size of 2×2?mm2 and a pitch distance of 2?mm. The average values of high and low impedances are 53.23 and 9.3?k?Ω, respectively. The maximum transmittance is about 74.2% at the wavelength of 692?nm. The multitouch panel based on high and low impedance patterns has been specifically designed to offer good adjacent touch resolution and sensitivity for reality multitouch applications. In addition, the patterned design and the algorithm matrix provide unlimited multitouch points and avoid ghost points.     

适用于光突发交换网的可编程光缓存器

提出了两种适用于光突发交换网的可编程光缓存器结构：交叉型和多端口开关型.两种结构都能满足突发包缓存的超长性和可变性的要求,且结构简单紧凑,成本低,可扩展.交叉型缓存器通过指定信号在每个子缓存模块的光纤环中的循环次数即能实现可变时间的延迟.多端口开关型缓存器通过指定信号在两个多端口开关相应端口与所接光纤延迟线组成的光纤环中的循环次数实现可变时间的延迟.仿真结果表明,两种可编程光缓存器都能对光突发包实现ns级指定时间延迟,可用于解决光突发交换网突发包的冲突问题.     

Optical pulse compression using the temporal Radon-Wigner transform

The temporal Radon-Wigner transform (RWT), which is the squared modulus of the fractional Fourier transform (FRT) for a varying fractional order p, is here employed as a tool for pulse compression applications. To synthesize the compressed pulse, a selected FRT irradiance is optically produced employing a photonic device that combines phase modulation and dispersive transmission. For analysis purposes, the complete numerical generation of the RWT with 0 < p < 1 is proposed to select the value of p required for pulse compression. To this end, the amplitude and phase of the signal to be processed should be known. In order to obtain this information we use a method based on the recording of two different FRT irradiances of the pulse. The amplitude and phase errors of the recovered signal, which are inherent to the recording process, are discussed in connection with the RWT production. Numerical simulations were performed to illustrate the implementation of the proposed method. The technique is applied to compress signals commonly found in fiber optic transmission systems, such as chirped gaussian pulses, pulses distorted by second and third-order dispersion and nonlinear self-modulated pulses.     

Optical implementation of orthogonal frequency-division multiplexing using time lenses

Orthogonal frequency-division multiplexing is implemented in optical domain using the Fourier transforming properties of time lenses. It is shown that the third- and higher-order dispersions of the transmission fiber can be significantly suppressed using the proposed scheme.     

Engineering implementation of a hybrid optical correlator using SLMs

Optical correlators have been widely used for such applications as automatic target identification, invariant pattern recognition and machine vision. In hybrid optical correlators, Spatial light modulators (SLMs) are used to dynamically update the input and the filter. However, implementation is difficult because of the interference of “ghost” images; rigorous requirements for filter registration, accurate and effective filter sizing and complex valued filtering functions. This paper proposes some practical approaches to handle these issues and provides engineering details of how to build a hybrid optical correlator, where a SLM serves as an updateable intensity filter for real-time pattern recognition.     

阴影像与眼像差仪的几何光学原理

Howland像差仪是一种由正负柱透镜中间夹着格栅组成的系统。它通过检出人眼透过像差仪所视的变形格栅图中的偏移变形量,来获得对应的人眼的波像差信息。建立了该系统的等效光学成像模型,从格栅所成阴影像的概念出发,得到其成像公式,给出人眼波像差计算方法。     

Optical encoder based on Fractional-Talbot effect using two-dimensional phase grating

This work presents an optical encoder that uses a two-dimensional phase grating. Rather than using a four-windowed scanning grating, this design with a special two-dimensional phase index grating generates two sinusoidal signals that are mutually phase-shifted by 180°. Afterwards, two large-areas, specially structured index grating generates the four 90° electrically phase-shifted scanning signals. The special design of the two-dimensional phase index grating provides more accuracy of phase-shift by using the fact that the  + 1 and −1 diffraction orders are intrinsically phase-shifted from one another by 180°. The gap between the phase index grating and mail scale was increased to three quarters of Talbot distance. The tolerance of gap between the index and main grating is 0.1 mm. The tolerance of yaw motion is ± 0.25°.     

Optical manipulation at planar dielectric surfaces using evanescent Hermite-Gaussian light

We show that a set of high order Hermite-Gaussian light beams when internally reflected at a dielectric/vacuum interface can generate well-defined evanescent light modes in each of which the intensity distribution is confined to a sub-wavelength region near the interface outside the dielectric. We suggest that this could greatly facilitate lateral optical manipulation of nano-particles and neutral atoms along the interface. Equally significantly, the scenario could lead to the formation of two-dimensional optical potential arrays and surface optical lattices that could form a suitable architecture for the implementation of quantum computing using neutral atoms.     

光学多通投影相关矩阵—矢量乘法器

基于几何光学的投影相关原理,本文提出了用非相干多通投影相关器作矩阵-失量乘法运算的新方论;讨论了这种矩阵矢量乘法器的一般结构形式和物理极限;并给出了实验结果,实验表明该方法简单易行.     

Optical implementation of (3, 3, 2) regular rectangular CC-Banyan optical network

CC-Banyan network plays an important role in the optical interconnection network. Based on previous reports of (2, 2, 3) the CC-Banyan network, another rectangular-Banyan network, i.e. (3, 3, 2) rectangular CC-Banyan network, has been discussed. First, according to its construction principle, the topological graph and the routing rule of (3, 3, 2) rectangular CC-Banyan network have been proposed. Then, the optically experimental setup of (3, 3, 2) rectangular CC-Banyan network has been designed and achieved. Each stage of node switch consists of phase spatial light modulator (PSLM) and polarizing beam-splitter (PBS), and fiber has been used to perform connection between adjacent stages. PBS features that s-component (perpendicular to the incident plane) of the incident light beam is reflected, and p-component (parallel to the incident plane) passes through it. According to switching logic, under the control of external electrical signals, PSLM functions to control routing paths of the signal beams, i.e. the polarization of each optical signal is rotated or not rotated 90° by a programmable PSLM. Finally, the discussion and analysis show that the experimental setup designed here can realize many functions such as optical signal switch and permutation. It has advantages of large number of input/output-ports, compact in structure, and low energy loss. Hence, the experimental setup can be used in optical communication and optical information processing.     

Optical mm-wave generation by using external modulator based on optical carrier suppression

In this paper, we have theoretically investigated the transmission performance of the optical millimeter (mm)-wave generated by using an external modulator based on optical carrier suppression for the first time. According to our theory, the data signals carried by the optical mm-wave are transmitted in the dispersion fiber without fading but are degraded greatly because of the time shift of the code edges, which still limits the transmission distance. The experimental results agree well with our theory.