一种利用傅里叶频谱测量焦距的新方法

介绍一种利用傅里叶频谱测最球面透镜、柱面透镜和环曲面透镜单色光焦距的方法。仪器装置简单,调试方便,测量精度可达0.30%。采用光电扫描及微机处理,可以实现自动化测量,而且还可以测量不可见光下的透镜焦距。     

用全息元件实现变形分数傅里叶变换

提出用全息元件实现变形分数傅里叶变换 .用全息方法制作在两个方向上具有不同焦距的变形柱透镜 ,且两方向上的焦距可随全息元件记录条件不同而改变 .用此元件实现了在不同方向上具有不同阶的变形分数傅里叶变换 ,讨论了用全息元件实现这种变换的条件 .并提出用此元件构成一种新的光学安全认证系统 ,给出了实验结果     

分数傅里叶变换频谱干涉法测量透镜焦距

对两相同物体同时实施分数傅里叶变换,通过测量其频谱干涉的条纹间距获知透镜焦距。该方法装置简单、操作方便、测量精度高、易于自动化处理,在光学测量中具有实用价值。     

对称双圆孔傅里叶变换干涉条纹法测焦距

提出用照相缩微法制作一个小孔距对称双圆孔作为待测透镜傅里叶变换输入函数,利用其傅里叶变换频谱面上的干涉条纹间距的测量值计算透镜焦距。该法装置简单,调节方便,测量精度较高。分析了测量原理和测量误差,并给出了与理论分析相符的结果。     

分数傅里叶变换光学实验基本单元的参量选择

以实现分数傅里叶变换的不等焦距双透镜模式为研究对象,分析了其与单透镜模式的等效性,给出了各种光学单元基本参量选择的判定法则。计算机模拟实验证明了结论的可靠性与可行性。     

单透镜成象的分数傅里里叶变换分析

利用描述光波傍轴传输的光学分数傅里叶变换基本关系式,对单透镜系统进行分析,结果表明,单透镜系统可实现任意阶分数傅里叶变换,Lohmann第一类光学分数傅里叶变换装置是其特例,单透镜成像过程是进行阶次为π的分数傅里叶变换,进一步表明光学分数傅里叶变换的物理实质是光波的菲涅耳衍射。     

基于基本光学单元的分数傅里叶变换算法

提出两种分数傅里叶变换数值计算新方法。本文用分数傅里叶变换描述信息在光学系统中的传输过程 ,分别基于分数傅里叶变换与菲涅尔变换之间联系和基于基本光学单元 (薄透镜及其组合 )实现分数傅里叶变换。该算法与光传输物理过程有着直观的联系 ,计算时光学系统的焦距、距离等参数可调。避免了传统算法中“变换核”等复杂计算 ,便于计算复杂光路和缩短计算时间。以三种飞机 (及字符 )光学模式识别实验为例 ,给出了空域 -频域变换混合光路的计算流程与结果     

频谱分析法测量傅里叶透镜焦距的研究

本文阐述了传统方法测量傅里叶透镜焦距存在的问题,提出应用频谱分析方法测量傅里叶透镜焦距。在理论分析和实验方法方面作了较详细的论述,解决了技术关键,提高了测量精度和稳定性,精度≤0.30％。该方法稍加修改,还可用于测量一般成象透镜焦距。     

利用全息透镜阵列实现多通道分数傅里叶变换

提出利用全息透镜阵列来实现多通道分数傅里叶变换技术。分析了全息透镜阵列的制作原理,对多个物体实现了分数阶次各不相同的多通道分数傅里叶变换,并与光学透镜实现的实验结果进行了比较,两者的分数频谱互相一致。这种技术在多通道光学信息处理系统及多目标图像识别系统等方面有非常重要的应用。     

分数傅里叶变换的无透镜光学实现

利用球面波照射物体的自由空间非涅耳衍射,完成任意级次分数傅里叶变换的无透镜光学实现,给出了不同条件下远透镜模式基本参量的选择法则及其分类傅里叶变换的数学表达,计算机模拟实验证明了结论的可靠与可行。     

一种新的盲多用户检测最大似然方法

线性受限最大似然盲多用户检测是盲多用户检测中的一类重要方法,现有的限制方法不能保证目标用户的最优解落在限制的搜索空间中,因此在理论上不能达到最优解。提出了一种新的限制方法,能保证目标用户的最优解落在限制的搜索空间中,因此保证算法收敛到目标用户。与现有方法相比,这里给出的算法结构简单,降低了运算复杂度。仿真试验表明其具有较低的误码率和较高的系统容量。     

DIRECT SOLUTION BY 2-D AND 3-D FINITE ELEMENT METHOD ON FORWARD PROBLEM OF LOW FREQUENCY CURRENT FIELDS IN INHOMOGENEOUS MEDIA

The paper adopts finite element method to analyze the forward problem of low-frequency current fields in inhomogeneous media. Firstly, the direct solution of 2-D and 3-D scalar potential is given. Secondly, the technique of covering finite elements for problems with movement has been presented; namely, when the place of testing point moved, the meshing data will be produced automatically to avoid re-meshing and distortion of the mesh. Thirdly the free and prescribed potential method is used to make the finite element coefficient matrices. Then this paper provides the result of a validity test obtained by simulating the laterolog-3 logging, compared with the numerical model-matching method. Finally, the MLL response is calculated.     

Synthesis of Distributed Phase-Locked Oscillators

This paper describes a type of distributed oscillator which combines the functions of distributed amplifiers (DAs), distributed transversal filters (DTFs), and distributed mixers (DMs). Nonlinear feedback of the kind used in mode-locked laser (MLL) systems is used in order to obtain phase locking between the resonant frequencies within the oscillator. The theory of operation is given and a tuning procedure for the tap weights of the distributed oscillator aimed at achieving a desired state of oscillation is presented. The impact that the nonideal components of the oscillator have on its performance is discussed. Through simulation it is shown that the effects of transmission line loss, uneven tap weight spacing and terminal impedance mismatch can be mitigated by properly adjusting the tap weights of the oscillator. Examples of waveform synthesis are given in which different periodic waveforms are produced by the oscillator including those found in an MLL and a waveform suitable for impulse based ultra-wideband systems.      

Magnitude locked loop

A control loop which maintains constant the magnitude of a transfer function is proposed. This loop is named the magnitude-locked loop (MLL). It is shown that it can perform most of the functions of the phase-locked loop. Several configurations can be chosen for the transfer function. The best, selected for its minimization of error, is presented     

多波长相干光注入锁定的波长跟踪自动化控制

本文基于全网光同步的超密集波分复用无源光网络(ultra-dense wavelength division multiplexing passive optical network, UDWDM-PON),对多波长注入锁定的稳定性进行了研究,提出了一种波长跟踪控制方法：用光电探测器(photo-diode, PD)接收从激光器(slave laser diode, SLD)的光信号并进行滤波与检波处理,所得信号用于建立SLD参数分布模型并进行线性扫描控制。该方法经基于LabVIEW程序控制与数据采集(data acquisition, DAQ)的仪器实验验证后,对相关驱动电路进行了模块化改良,采用基于微控制单元(microcontroller unit, MCU)的控制,使得该控制模块具有更高控制精度、更易封装的特点,从而能更好应用于多波长光的多路注入锁定当中。本文采用主动锁模激光器(mode-locked laser, MLL)作为多波长光源,对双路SLD的注入锁定进行了验证与对照实验,结果表明：在相同注入条件下,采用波长跟踪控制模块的注入锁定组具有更佳的稳定性。     

锁幅环路（MLL）及其应用

本文描述一个能使传递函数(TF)不管在任何输入频率时都能保持不变的新型控制环路——锁幅环路(MLL)。文中导出单一正弦信号时,输入频率与输出DC电压的线性关系,并讨论其可能应用。实验证明[1],MLL可执行锁相环路(PLL)的绝大部分功能。     

Monolithic Mode-Locked Laser and Optical Amplifier for Regenerative Pulsed Optical Clock Recovery

We experimentally demonstrate optical clock recovery using a novel mode-locked laser (MLL) monolithically integrated with an output semiconductor optical amplifier. The laser's mirror placement is determined using lithography, allowing for mode locking and clock recovery at the exact frequency of the design (35.00 GHz), which is easily scalable to 40 GHz or higher. The design is compatible with other photonic integrated circuit components, enabling integrated signal processing with MLLs. The device generates pulses at 35.0-GHz repetition rate with 6-ps pulsewidth, over 12-dB extinction ratio (ER), and 8.3-dBm output power. Among other regenerative capabilities, the device performs optical clock recovery with 50% jitter reduction from a degraded input signal with low ER     

Optical microwave generation and transmission experiments in the12- and 60-GHz region for wireless communications

Experiments on the optical generation and transmission of millimeter-wave radio signals are reported. The millimeter-wave signals are generated by heterodyning the optical spectral lines of a mode-locked laser (MLL) or of two or more semiconductor lasers at an optic/millimeter-wave converter (OMC). 70-, 140-, and 155-Mb/s data transmission experiments have been carried out successfully in optical single-channel and multichannel systems at radio frequencies of 12 GHz and 58-70 GHz. Bit-error-rate measurements yielded error-free transmission and no error floor was observed. A monolithically integrated tunable optical-signal source was developed and used for generating the millimeter-wave signals. This technology promises a high cost-saving potential for applications in radio-over-fiber systems     

Fully programmable ring-resonator-based integrated photonic circuit for phase coherent applications

A novel ring-resonator-based integrated photonic chip with ultrafine frequency resolution, providing programmable, stable, and accurate optical-phase control is demonstrated. The ability to manipulate the optical phase of the individual frequency components of a signal is a powerful tool for optical communications, signal processing, and RF photonics applications. As a demonstration of the power of these components, we report their use as programmable spectral-phase encoders (SPEs) and decoders for wavelength-division-multiplexing (WDM)-compatible optical code-division multiple access (OCDMA). Most important for the application here, the high resolution of these ring-resonator circuits makes possible the independent control of the optical phase of the individual tightly spaced frequency lines of a mode-locked laser (MLL). This unique approach allows us to limit the coded signal's spectral bandwidth, thereby allowing for high spectral efficiency (compared to other OCDMA systems) and compatibility with existing WDM systems with a rapidly reconfigurable set of codes. A four-user OCDMA system using polarization multiplexing is shown to operate at data rates of 2.5 Gb/s within a 40-GHz transparent optical window with a bit error rate (BER) better than 10/sup -9/ and a spectral efficiency of 25%.     

模块化电力电子实验装置研发

旧式电力电子实验装置不能满足实验课程对学生设计能力和工程思维的培养需求,为此本文提出基于模块化思路设计的新型电力电子实验装置。本文设计的实验装置在提高实验效率的同时满足实验课程对学生的培养要求。对装置的具体实现和组成作了简要介绍,同时给出了教学方法的设计。并通过一个具体的实验教学实例,简述了实验流程。这种教学方法贴近实际工程开发流程,有助于学生整体实践能力的培养。