All optical active high decoder using integrated 2D square lattice photonic crystals

The paper introduces a novel all optical active high 2 × 4 decoder based on 2D photonic crystals (PhC) of silicon rods with permittivity of ε = 10.1 × 10^?11 farad/m. The main structure of optical decoder is designed using a combination of five nonlinear photonic crystal ring resonator, set of T-type waveguide, and line defect of Y and T branch splitters. The proposed structure has two logic input ports, four output ports, and one bias input port. The total size of the proposed 2 × 4 decoder is equal to 40 μm × 38 μm. The PhC structure has a square lattice of silicon rod with refractive index of 3.39 in air. The overall design and the results are discussed through the realization and the numerically simulation to confirm its operation and feasibility.     

A novel proposal for all optical 3 to 8 decoder based on nonlinear ring resonators

In this paper, a 3 to 8 optical decoder was proposed using nonlinear photonic crystal ring resonators. For realizing the 3 to 8 decoder, we combined seven 1 to 2 optical decoders. In the proposed structure, X, Y and Z serve as input ports. By combination of these ports, one can control which output port to be ON. The maximum time delay of the proposed structure is about 6?ps.     

Study the role of non-linear resonant cavities in photonic crystal-based decoder switches

In this paper, we are going to design and propose a novel structure for all optical decoder. The proposed structure is composed of optical power splitters and a four-port optical switch. The four-port optical switch simply is a non-linear optical demulitiplexer. For achieving non-linear behaviour for the demultiplexer, we will employ defect rods made of doped glass which has high Kerr coefficient. The final structure has three input ports and four output ports. Port E acts as enable port, which will be used activating or deactivating the total structure. A and B are the control ports, by which one can control when the structure is active, which port of the structure to be active. The optical intensity of the input ports required appropriate operation of the structure is about 20 W/μm². The maximum switching frequency of the proposed structure is 2 GHz. Reduced input optical intensity is the main characteristics of the present work. Numerical methods such as plane wave expansion and finite difference time domain were used for performing the required calculations.     

All-optical digital 4 × 2 encoder based on 2D photonic crystal ring resonators

The photonic crystals draw significant attention to build all-optical logic devices and are considered one of the solutions for the opto-electronic bottleneck via speed and size. The paper presents a novel optical 4 × 2 encoder based on 2D square lattice photonic crystals of silicon rods. The main realization of optical encoder is based on the photonic crystal ring resonator NOR gates. The proposed structure has four logic input ports, two output ports, and two bias input port. The photonic crystal structure has a square lattice of silicon rods with a refractive index of 3.39 in air. The structure has lattice constant ‘a’ equal to 630 nm and bandgap range from 0.32 to 044. The total size of the proposed 4 × 2 encoder is equal to 35 μm × 35 μm. The simulation results using the dimensional finite difference time domain and Plane Wave Expansion methods confirm the operation and the feasibility of the proposed optical encoder for ultrafast optical digital circuits.     

A novel proposal for all-optical compact and fast XOR/XNOR gate based on photonic crystal

In this paper, we aim to design an all-optical device, which can perform XOR and XNOR functions in a single structure. The proposed structure will be realized by cascading two nonlinear resonant rings. The functionality of the proposed structure is based on controlling the optical behaviour of optical rings via optical intensity. The final structure has one bias and two input control ports, along with two output ports. One port acts as an XOR and the other acts as an XNOR gate. The maximum delay times for the XOR and XNOR gates are 1.5 and 2.5?ps, respectively. Therefore, the working bit rates for the XOR and XNOR gates are 666 and 400?Gbit/s, respectively.     

Spectral changes and 1 X N spectral switches in the diffraction of partially coherent light by an aperture

The off-axis and on-axis spectra in the far zone of an aperture for the case in which a particular class of partially coherent light with a broad spectrum is diffracted by an aperture are studied. It is shown that the spectrum in the far zone is generally different from that at the aperture; i.e., the spectrum is split into two or more peaks. Moreover, the spectrum varies with the diffractive angle. For a fixed diffractive angle, the spectral shift, defined as the difference between the frequencies at which the observed spectrum and the spectrum at the aperture take their maximum, shows a gradual change with the change in the coherence at the aperture. However, as the coherence reaches some critical values, the spectral shift exhibits a rapid transition; i.e., spectral switch occurs. The coherence that causes the spectral switch to take place is different for different diffractive angles. Therefore we propose a new kind of 1 x N spectral switch, where N detectors (output ports) are placed at different diffractive angles in the far zone, and the spectral shifts at different detectors are measured. By adjusting the coherence of the aperture (input port) to the desired values, we obtain a rapid transition of the spectral shift in the desired output ports.     

Nonreciprocal optical divider based on two-dimensional photonic crystal and magneto-optical cavity

We suggest and analyze a new nonreciprocal optical device based on two-dimensional photonic crystal and a magneto-optical cavity that simultaneously fulfills two functions: division of the input signal and isolation of the input port from two output ones. At the central frequency, the division of the signal between the output ports is -3 dB and the isolation of the input port from the output ones is about -25 dB. For the level -20 dB of this isolation, the calculated bandwidth is around 100?GHz at the wavelength 1.5?μm.     

Sparse monolithic compliant mechanisms using continuum structural topology optimization

A formulation for design of continuous, hinge‐free compliant mechanisms is developed and examined within a continuum structural topology optimization framework. The formulation makes use of two distinctly different sets of springs, the first of which are artificial springs of relatively large stiffness attached to the input and output ports of the mechanism model, and the second of which are springs attached only to the output port with smaller stiffnesses that represent the resistance of the workpiece as it is manipulated by the mechanism. The proposed formulation involves solving two nested optimization problems. In the inner problem the arrangement of a constrained amount of structural material is optimized to maximize the mechanism's mutual potential energy in response to a force loading at the input port while working against the stiff artificial springs on the input and output ports. As the relative stiffness of the artificial springs increases, the material continuity of the mechanism also increases to the point where de facto ‘hinge’ regions are eliminated. In the outer problem, the artificial springs are removed and one solves for an appropriate amount of structural material that yields the desired finite deformation compliance characteristics of the mechanism when working against the real workpiece resistance. Different aspects of the proposed formulation are demonstrated on a number of examples and discussed. Copyright © 2004 John Wiley & Sons, Ltd.     

24 GHz miniaturised phase-selectable balun

The design, fabrication and test of a uniform microstrip and a slow-wave microstrip version of a two phase state balun based on an ultra compact 90deg quasi-lumped hybrid coupler design are presented for use in the 24 GHz Industrial, Scientific and Medical frequency band. The balun, realised using Gallium Arsenide integrated circuit technology, has the property that when fed from one of its input ports it provides a differential phase of 180deg at its output ports and when fed at its second input port it provides 0deg phase shift between output ports. The lambda/8 quasi- lumped coupler core reported occupies 0.15 of the area of a conventional quarter-wavelength coupler and has 0.5 dB insertion loss. The slow-wave version of the coupler is 40% shorter than the lambda/8 quasi-lumped coupler and exhibits 0.9 dB insertion loss.     

The designs of a scalable optical packet switching architecture

Abstract

This paper proposes a new switching architecture to be used in all optical packet switching networks. The proposed switch is derived from an original 2 × ?2 two‐stage multi‐buffer switched delay line based optical switching node, known as an M‐Quadro node. By incorporating bypass lines into the M‐Quadro architecture and employing a novel switch control strategy, the optical packet switching node can effectively resolve packet contentions, thus reducing the packet deflection probability substantially. Furthermore, we show that such architecture is scalable for a generic multiple stages optical packet switch with a larger number of input/output ports.     

Novel compact microstrip interdigital bandstop filters

A novel compact microstrip interdigital band-stop filter is designed and implemented. The structure is similar to that of an interdigital capacitor. The input port and output ports are connected to form the bandstop characteristic. This proposed filter with microstrip interdigital geometry not only exhibits good bandstop characteristics and a tunable central frequency, but it also is easy to fabricate and integrate. The features of this microstrip interdigital bandstop filter are smaller than those of the conventional bandstop filter. Simulation results closely correspond to the experiments.     

Electro-optical logic application of multimode interference coupler by multivalued controlling

Electro-optical hybrid logic is a potential solution to implement both electrical and optical signal processing, which receives analog or digital, electrical or optical signals and produces logic signals in a desired manner. In light of the transfer matrix theory, we found that one can steer light into different output ports of a multimode interference coupler by controlling the phases in a multivalued manner on the image-extended arms. This implementation acts as an analog-to-digital convertor from electric domain to optical domain. Also, an electrical-to-optical 2-to-2(2) binary-coded decoder is described and examined by the 3D beam propagation method.     

All-optical photonic crystal AND,XOR, and OR logic gates using nonlinear Kerr effect and ring resonators

In this article, two structures are proposed for all-optical AND, XOR, and OR logic gates based on nonlinear photonic crystals. The proposed structures include a Y-junction and ring resonator-based limiters. Two different structures are designed as the limiter in order to produce AND–XOR and AND–OR logic gates. Nonlinear rods of proposed structure have been used in order to create the frequency shift for different values of input power. Finite difference time domain method has been utilized to simulate the performance of proposed logic gates. Simulation results show that the smallest ON–OFF logic-level contrast ratio for the structures proposed for AND–XOR and AND–OR logic gates are 20.29 dB and 16.7 dB, respectively.     

Switched-boost action: a phenomenon for achieving time-division-multiplexed multi-port power transfer for nanogrid applications

Multi-port power converter topologies are used to interface multiple terminals (source or load) using a single converter topology. In this paper, the possibility of using switch node of a power converter stage as interface to multiple output stages has been investigated. This interfacing of multiple outputs at the same switch node occurs using time-division multiplexing of the available input power. The multiplexing of input power into different ports occurs using a phenomenon that is denoted as ‘switched-boost action’ in the work and this concept has been illustrated using the boost converter topology. The proposed approach has been used to interface the boost-derived architectures to different types of outputs—ac, dc and isolated dc. The circuit operation has been validated using experimental results. These circuits have been proposed as possible candidates for nanogrid applications.     

Photonic encoder and decoder for optical code-division multiplexing with time-to-space converters and angle-multiplexed holograms

A photonic encoder-decoder pair for optical code-division multiplexing (OCDM) that uses time-to-space converters and angle-multiplexed holograms is proposed. The encoder converts the pulse from each input port into a specific code and multiplexes input signals into the output port. The hologram in the decoder generates a correlation waveform between the transmitted code and the recorded code. The performance of the OCDM system with the encoder-decoder pair is estimated. The maximum spectral efficiency for 8-bit length orthogonal codes in the worst case at a bit-error rate of 10(-9) is 0.17 (bits/s)/Hz when the number of channels is 8.     

加速无限输出缓冲ATM交换机性能分析

讨论了带有内部加速的无限输出缓冲ATM交换机，提出了一种计算信元丢失率及平均时延的分析模型，并进行了计算机仿真。仿真结果表明，该分析模型是十分准确的。     

加速有限输出缓冲ATM交换机性能分析

讨论了带有内部加速的有限输出缓冲ATM交换机,提出了一种计算信息元丢失率及平均时延的分析模型,并进行了计算机仿真,仿真结构表明,该分析模型是十分准确的。     

Optical programmable Boolean logic unit

Logic units are the building blocks of many important computational operations likes arithmetic, multiplexer-demultiplexer, radix conversion, parity checker cum generator, etc. Multifunctional logic operation is very much essential in this respect. Here a programmable Boolean logic unit is proposed that can perform 16 Boolean logical operations from a single optical input according to the programming input without changing the circuit design. This circuit has two outputs. One output is complementary to the other. Hence no loss of data can occur. The circuit is basically designed by a 2×2 polarization independent optical cross bar switch. Performance of the proposed circuit has been achieved by doing numerical simulations. The binary logical states (0,1) are represented by the absence of light (null) and presence of light, respectively.     

基于DEA视窗分析的渤海湾地区港口内部运营效率

既往对港口效率的研究大多仅考虑空间维度,忽略时间的作用。为了弥补这一不足,运用DEA视窗分析模型,从空间和时间两个维度出发,利用面板数据,对渤海湾地区三大主要港口的内部运营效率进行研究,并利用在DEA相对有效面上的投影分析,明确港口偏离有效的原因。此外,运用灰色关联模型对影响港口效率的因素进行了测算。研究发现,青岛港内部运营效率较高,其次为天津港,而大连港则一直处于非DEA有效状态;投入拥挤、产出不足以及资源配置不合理是造成非DEA有效的主要成因;各投入要素对三大港口内部运营效率的影响程度存在较大差异。     

Experimental study of the phenomenon of 1 x N spectral switch due to diffraction of partially coherent light

Spectral properties of a class of partially coherent light with spectral profiles of varying bandwidths are studied on diffraction by a circular aperture in the far zone for different diffractive angles, i.e., for on-axis and off-axis points on the observation plane. It is found that the spectrum of the light in the far zone is different from that at the aperture plane. This change in the spectrum is termed spectral shift, which is found to be different at different diffractive angles. The spectral shift for a fixed diffactive angle shows a gradual change. However, for a critical value of the coherence at the aperture plane, the spectral shift shows a rapid transition, termed spectral switch. For different diffractive angles the coherence that causes the spectral switch also differs. Therefore the phenomenon of 1 x N spectral switch (consisting of one input port and N output ports) is studied experimentally.