衍射光学器件精细化设计及光强失真机理

基于基尔霍夫标量衍射理论,详细分析了输入、输出平面及变换函数抽样间距的选取原则.系统建立了衍射光学器件精细化设计的抽样理论,深入研究了输出图样在非抽样点上的光强失真机理.在定义衍射光学器件光能利用率、顶部不均匀性等性能评价参数的基础上,以盖师贝格-撒克斯通(GS)算法设计一维光束整形器件为例,探讨了输出图样在非抽样点上的光强失真和输出平面抽样间距间的关系,通过模拟计算验证了精细化设计时输入与输出平面抽样理论的有效性.     

Ultrafast soliton-trapping AND gate

An ultrafast, all-optical, soliton-trapping AND gate that consists of a birefringent optical fiber followed by a frequency filter is demonstrated. The gate is sensitive to the timing of the input pulses and provides an output with a large energy contrast. The performance of the gate is characterized by varying the total input energy, the ratio between the energies of the two input pulses, and the arrival-time difference between the input pulses. It is shown that the gate efficiency (characterized by its ON-OFF contrast ratio) increases with increasing pulse energy up to the limit where Raman effects become dominant in the fiber, and the optimal performance of the gate is obtained with two input solitons having equal energies. The gate efficiency degrades with increasing difference of arrival time of the two input pulses, but a contrast ratio of 5:1 can still be obtained for a full pulse width of timing mismatch. The experimental results are in agreement with numerical simulations using the coupled nonlinear Schrodinger equations     

基于小波多尺度综合的低对比度目标识别

光电混合联合变换相关器能够对目标进行自动探测识别和跟踪。为使联合变换相关器对低对比度目标进行有效探测与识别,提出了一种基于小波多尺度综合的边缘提取新方法,对输入图像进行预处理。计算机模拟实验和光学实验证明,该方法使相关器在输入图像对比度低、信噪比较低时仍然能够产生较强的相关峰输出,扩展了光电混合联合变换相关器的应用范围。     

Improved OBS Burst Assembly with a Buffer Safety Space in Unit Input Bit Rate

A burst assembly scheme at the edge routers in optical burst switched networks (OBSNs) is presented for setting up more universal, realistic, and high-powered networks. For the first time, the concept of unit input bit rate is introduced to improve universality. In addition, various factors limiting burst length are discussed, while considering service requirement and hardware architectures. Then, a novel burst assembly algorithm with a buffer safety space is proposed. Based on the above, the assembly process in optical burst switching at edge routers is simulated, and its influence on burst creation, burst length distribution, packet loss ratio, total output data, and valid data ratio are discussed. The results show that the scheme can provide more efficient QoS guarantee in optical burst switched networks, even for 32 random packet sources at an edge router, the packet loss ratio is to 5 × 10⁻⁵, and the valid data ratio reaches 99.7%.     

Ultra-fast all-optical encoder using photonic crystal-based ring resonators

Optical encoders are one of the important optical logic devices required in optical communications and optical signal processing. In this paper, we proposed a novel structure for designing an all-optical 4-to-2 optical encoder based on photonic crystals. For this purpose, four photonic crystal-based ring resonators were located between the input and output ports which results in improved coupling efficiencies between input and output waveguide and reduced cross-reflection between the input ports. The central wavelength of the photonic crystal-based ring resonators is 1555 nm. However, due to its wide bandwidth the proposed structure can be used for a wide range of optical waves. In the proposed structure, the delay time and the ON/OFF contrast ratio are 1.8 ps and 9.2 dB, respectively. The other advantages of the proposed structure is that we did not use nonlinear materials in designing the proposed structure, so there is no need for high amount of optical intensities.     

All-optical bit-pattern matching with photonic switching arrays

An all-optical XOR logic circuit is demonstrated using photonic switching arrays that integrate multiple-quantum-well reflection modulators and phototransistors. The switching element performs a Boolean logic A B operation on two binary input light signals that are separately incident on the phototransistor and modulator. The XOR logic function is derived by optical coupling of the switching elements. The device features high contrast that enables high-speed bit pattern matching in parallel     

Ultrafast all-optical pattern matching using differential spin excitation and its application to bypass/drop self-routing for asynchronous optical packets

This paper presents a novel scheme for ultrafast all-optical pattern matching using the differential spin excitation in semiconductor multiple quantum wells (MQWs). In a demonstration of an all-optical pattern matching between two 100-Gb/s 16-bit optical packets, the contrast ratio of the photodiode (PD) output from the pattern matcher, between the pattern matched and the pattern-unmatched cases, was more than four for packets with a 2-dB power fluctuation. As an application of the pattern matcher to optical-packet-switched ring networks, bypass/drop self-routing is demonstrated for asynchronous 100-Gb/s 32-bit optical packets with 8-bit labels. In the experiment, a label of an incoming packet was compared to a local address (LA) given to a node in the optical domain. By changing the pattern of the LA packet instead of that of the incoming packet, the pattern matching was carried out for packets with various kinds of patterns. The contrast ratio of the PD output was more than six for all patterns.     

一种最小可分辨温差计算方法

提出了一种红外成像系统的最小可分辨温差(Minimum Resolvable Temperature Difference,MRTD)预测方法。该方法以线性系统理论为基础,利用调制传递函数建立红外成像系统模型,模拟生成不同空间频率的标准四杆靶(长宽比为7:1);通过分析四杆靶的二维(横向和纵向)成像质量,引入对比度修正因子,获取系统输出的四杆靶与背景的温差;利用阈值输入对比度温差,得到系统的MRTD。仿真试验表明,该方法预测的MRTD值与实际测量值一致。     

Image-storage panels based on field-effect control of conductivity

Using the principle of field-effect conductivity control, a new method of image storage has been demonstrated. Based on this a new type of solid-state image panel has been developed capable of producing a stored luminescent image. This employs an electroluminescent powder layer for generation of the output image and a ZnO powder layer for control and storage purposes. In operation the exposed ZnO surface is first uniformly corona charged to a negative potential to reduce its conductivity and "erase" old information. Following this the panel is exposed to an optical image which discharges local areas, producing a stored charge pattern on the ZnO surface. In accordance with this charge pattern a conductivity pattern is created in the ZnO layer which in turn controls the luminescent output of corresponding areas of the adjacent phosphor layer. For producing a stored image, approximately one microjoule/cm²of input radiation in the wavelength range of 3500-4000 Å is required. Reciprocity exists between the exposure time and the radiation level. Stored images have a brightness as high as 20 footTlamberts and a maximum contrast ratio of about 100:1 and exhibit good halftones. Although a hafftone output image can be retained for periods of the order of an hour, it can be rapidly erased when desired by recharging the ZnO surface to a uniform negative potential. Present panels are 12 by 12 inches in size and have a limiting resolution between 400 and 800 TV lines.     

利用光纤参量放大器构成全光与门

利用光纤参量放大器(FOPA)中的波长转换特性完成全光与逻辑运算。以波长转换的原理为基础, 从两路输入光波的四种码字组合的相位匹配关系入手, 证明了FOPA的闲散光输出与两路输入光波的逻辑关系符合与门的逻辑。通过龙格-库塔方法数值求解非线性耦合方程组, 仿真证实了FOPA的输出与输入光波满足全光与门的逻辑, 研究了此全光与逻辑门闲散光波的输出功率随光纤长度、输入光波的功率比值以及输入光波波长位置的变化关系, 为实际中优化设计全光与门提供了参考。并对100 Gb/s的全光与逻辑运算中所应选择的输入光波脉冲宽度的问题进行了讨论。     

Wavelength selective optical logic and interconnects

A wavelength selective optical logic (WSOL) element that uses monolithically integrated wavelength selective optical input and output elements is described. Input optical signals are detected by photothyristors situated in an optical cavity which provides a highly selective response of a wavelength determined by the fabrication process. Output signals are generated by vertical cavity surface emitting lasers, whose lasing wavelengths can also be specified during the fabrication process. A vertical integration of these input and output elements that is suitable for wavelength selective optical logic and wavelength selective optical interconnect applications is proposed. The proposed circuitry is easily cascadable so that arbitrarily complex optical logic functions can be performed by WSOL devices in series. Several of the possible logic functions are described, including OR and AND gates, an adder, and a flip-flop     

A simulation study of adaptive burst assembly algorithms in optical burst switched networks with self-similar traffic sources

It has been extensively demonstrated that the traffic pattern in today’s Internet is Self-Similar. Burst assembly algorithms utilized in optical burst switched (obs) edge routers can be used to reduce the degree of self-similarity. This work investigates the impact of time and size-based burst assembly algorithms utilized in obs edge routers, on the self-similarity level of the output traffic. Both static and adaptive algorithms are examined. Our study is based on the opnet simulation tool focusing on the characteristics of the output traffic in the presence of self-similar input traffic. To estimate the Hurst parameter of the aggregated input and output traffic streams, we have applied various Hurst parameter estimators. The performance impact of the burst assembly algorithms in terms of burst assembly delay and its jitter is also assessed. Our study has shown that the burst assembly mechanism at the obs edge router reduces the self-similarity level of the output traffic and that this reduction depends on the parameters of the algorithm. Our results reveal that the proposed adaptive burst assembly algorithm performs better comparing to its non-adaptive counterpart.     

Resonant Dynamics of Nonlinear Optical Microdisks

An investigation into the relationship between two-photon-induced carrier dynamics and nonlinear optical resonance is carried out for an InP microdisk. A phenomenological model is developed and algebraic solutions are presented for the resulting bistability turn-on and turn-off transition points. It is shown that the offset between the operating wavelength and the un-illuminated resonance wavelength plays a critical role in defining the optical bus line intensity requirements at the input and the intensity contrast ratio at the output.     

自由空间奇数端口非对称型光开关研究

有别于传统的偶数端口对称型光开关设计,本文采用积木叠层方法设计,结构非对称、奇数端口的2×3和3×3光开关;各光开关基本功能单元结构类似,均由偏振光分束器(PBS)、相位型空间光调制器(PSLM)和反射镜组成;利用成熟的偏振控制技术实现信号光的控制和路由选择,有效避免路径的冲突与阻塞。这种设计具有结构简单紧凑、控制方便灵活、双向操作、与偏振无关、即插即用、易集成、易扩容和升级等特点。对2×2光开关单元的实验分析表明,该光开关插损小、串扰低和可靠性高,对于构建大规模的奇数端口和非对称结构的交换矩阵有帮助。     

Tuning technique to optimize input power of a cross-phase modulation wavelength converter

This paper proposes a tuning technique to optimize the input power of a cross-phase modulation wavelength converter (XPM-WC). The focus is on an output signal whose wavelength is the same as the input signal. The optimum input power can be easily set by keeping the output signal (not converted signal) power constant. Input continuous-wave (CW) power should be increased or decreased with increasing or decreasing input signal power so that the output signal power stays fixed at the optimum level. Observing the eye pattern of the converted signal is unnecessary. Wavelength conversion from a fixed optical channel to a random one (30 channels with 100-GHz spacing) is successfully demonstrated by using this technique. A low-power penalty (<1dB) and a low-power fluctuation (<1dB) were confirmed in all optical channels. An XPM-WC unit containing a variable CW light source and its level controller were fabricated and simultaneous and automatic operation was confirmed.     

A monolithically integrated optical differential amplifier forapplications in smart pixel arrays

A cascadable, optical differential amplifier with an active output is realized in AlGaAs-GaAs by the monolithic integration of three devices: A photodiode (PD), a light-emitting diode (LED) and a combination of a photodiode and a junction field-effect transistor (PINFET). A minimum optical switching power of 15 pW, an optical gain of more than 10⁶, a contrast ratio greater than 1000 and an optical output power of 17 μW are obtained. For a contrast ratio of 10, a switching energy of 2 pJ is required, resulting in a unity gain bandwidth of 4.2 MHz     

中国《电子投影机测量方法》标准解析

阐述了2006年中国刚刚颁布的<电子投影机测量方法>标准的起草原则、指导思想以及主要参数的测量方法,并重点对光输出、亮度、对比度、通断比、固定分辨力、输入格式等容易混淆的概念和重要参数进行了分析.     

Impact of crosstalk induced beat noise on the size of semiconductor laser amplifier based optical space switch structures

The size limitation of a semiconductor laser amplifier (SLA) based optical matrix-vector multiplier (MVM) switch structure arising from amplifier noise and crosstalk is investigated theoretically and experimentally. Computer simulation reveals that the number of input/output channels in such a switch structure may be limited to less than 60/spl times/60 if the contrast ratio of each SLA is 20 dB or lower.     

Noise and distortions limitations in the design of HFC CATV systems

The paper deals with HFC CATV systems. System parameters determinative in obtaining the desired carrier-to-noise ratio (CNR) and acceptable nonlinear distortions are considered. Formulae for the gain and the maximum number of RF amplifiers in the longest coaxial trunk line are developed. A mathematical model of the optical channel is suggested that makes it possible for the signal minimum level at the optical receiver input to be calculated if the value of CNR and the number of TV channels transmitted are known. Analytical expressions to determine the RF signal voltage in the input and output of the optical line are given that take into consideration the nonlinear distortions in the laser transmitter, the number of TV channels and the losses within the optical fiber and passive elements. Experimental results are given to illustrate the application of the formulae in the design of a HFS system section.     

A 90-dBΩ 10-Gb/s Optical Receiver Analog Front-End in a 0.18-μm CMOS Technology

A 10-Gb/s 90-dBOmega optical receiver analog front-end (AFE), including a transimpedance amplifier (TIA), an automatic gain control circuit, and a postamplifier (PA), is fabricated using a 0.18-mum CMOS technology. In contrast with a conventional limiting amplifier architecture, the PA is consisted of a voltage amplifier followed by a slicer. By means of the TIA and the PA codesign, the receiver front-end provides a -3-dB bandwidth of 7.86 GHz and a gain bandwidth product (GBW) of 248.5 THz-Omega. The tiny photocurrent received by the AFE is amplified to a differential voltage swing of 900 mV_pp when driving 50-Omega output loads. The measured input sensitivity of the optical receiver is -13 dBm at a bit-error rate of 10^-12 with a 2³¹-1 pseudorandom test pattern. The optical receiver AFE dissipates a total power of 199 mW from a 1.8-V supply, among which 35 mW is consumed by the output buffer. The chip size is 1300 mumtimes1796 mum