光纤偏振模色散的测量

介绍了时域法与频域法的几种偏振模色散(PMD)的测量方法，其中包括了一种新的测量方法——调制相移法。分别介绍了它们测量原理，并对各种方法进行了比较，概括了各种方法的优缺点。     

降低PMD的光纤拉丝扭转技术

随着光纤光缆产业的发展,国内不少光纤光缆企业正在扩建或新建光纤拉丝项目。由于高速大容量长途光纤通信系统对单模光纤PMD性能的日益重视,为了减轻单模光纤的PMD对通信系统性能的影响,可以在通信系统中对单模光纤的PMD进行补偿,但因光纤的PMD是个随机变量,这就大大提高了补偿器技术的复杂性及其成本。另一种方法则是采用在线光纤扭转技术来降低单模光纤的PMD值。而这种在线光纤扭转技术是用来降低单模光纤的PMD值的最简便,最有效,最实用的方式。本文旨在探讨光纤扭转技术的实施方法及其原理分析。     

G.655光缆中继段光纤链路PMD值测试研究

通过实用G.655光缆工程大量测试、对比验证：WS（波长扫描）法可作为ITU建议的PMD（偏振模色散）基准测量方法-IF（干涉）法的替代法;性能稳定,合格的G.655光缆敷设后PMD值影响很小;纤段串接后链路的PMD值可用文中引用的公式（1）计算,而等长纤段串接后PMD值可用简化的公式（2）计算,且由它推出当各段PMD值相等或接近时,它就是串接后光纤链路的值,此公式也适用G.652和G.655纤段串接后链路PMD值的计算,G.655纤链的PMD值不会因G.652纤段的接入而受影响和劣化。     

光纤光缆中的偏振模色散与旋转光纤

首先回顾了光纤与光缆中产生偏振模色散(PMD)的原因及其危害性。然后讨论了减小PMD的几种措施。重点综述了在光纤拉制过程中施加摇摆旋转来减小PMD的方法--旋转光纤。介绍了在拉丝生产线上测量光纤扭转角的方法，以保证得到低PMD的光纤。最后介绍了贝尔实验室进行的几项PMD稳定性的实验结果。     

光纤光缆中的偏振模色散与旋转光纤

首先回顾了光纤与光缆中产生偏振模色散(PMD)的原因及其危害性。然后讨论了减小PMD的几种措施。重点综述了在光纤拉制过程中施加摇摆旋转来减小PMD的方法——旋转光纤。介绍了在拉丝生产线上测量光纤扭转角的方法，以保证得到低PMD的光纤。最后介绍了贝尔实验室进行的几项PMD稳定性的实验结果。     

通信光纤及光子晶体光纤偏振模式色散的测量方法

从基本原理、系统配置和优缺点等方面系统阐述了国际电工委员会规定的四种标准偏振模色散测量方法—琼斯矩阵本征分析法、波长扫描计算法、波长扫描傅立叶变换法和干涉法,并进行了比较和分析。通过对大模场光子晶体光纤偏振模色散特性分析,说明了针对普通单模光纤制订的标准测量方法可应用于新型光子晶体光纤的PMD测量。     

光纤包层不圆度与偏振模色散间关系的研究

文章介绍了光纤偏振模色散(PMD)的基本概念及影响因素.通过一系列试验分析了光纤包层不圆度与PMD的关系,指出为控制光纤PMD的稳定性,提高光纤在绕盘状态下测得的PMD值的可信度,需要将光纤包层不圆度控制在一个较小的范围内.利用光纤旋转技术则可以延展这一控制范围.     

减小光纤PMD的新方案

首先介绍了几种从生产工艺上减小光纤偏振模色散的措施,并指出了各自的缺点。然后重点介绍在拉丝过程中加入了搓动轮,使光纤来回旋转,从而减小光纤的PMD的原理。对拉出的光纤的PMD进行了测试,给出了测试结果,同时对测试结果加以探讨,最后得出搓动轮的搓动次数与PMD的关系。     

单模光纤偏振模色散的测试

偏振模色散（PMD）在近年来成为光纤光缆的一个重要特性参数。本文着眼于PMD测试的原理和方法，首先指出注重PMD的统计特性是进行PMD测试的一个重要原则；继而按频域和时域对测试PMD的方法进行分类，并分析了目前常用的几种PMD测试方法，例如JME、WSEC、PSP、IF、WSFFT和POTDR法，讨论了它们各自的优缺点。最后对这些测试方法进行了有益的比较。     

偏振模色散的光域补偿方法研究

针对光纤传输中的偏振模色散(PMD)问题,研究和比较了现有PMD的光域补偿方法.利用等效啁啾技术,提出了一种基于啁啾光纤光栅的光域补偿方案,用具有光敏性质的保偏光纤制成啁啾光纤光栅,将其作为PMD补偿器中的时延线,实现了PMD的自适应反馈补偿.实验结果显示,该方案能有效补偿光纤传输中的PMD问题,提高光信号的传输质量.     

Sampling pulses with semiconductor optical amplifiers

We demonstrate three techniques to measure the instantaneous frequency and intensity of optical pulses using semiconductor optical amplifiers (SOAs). Four-wave mixing, gain-saturation, and interferometric switching through a nonlinear optical loop mirror are three mechanisms by which sampling is done. We have experimentally measured the intensity and chirp profiles of pulses with energies as low as 10 fJ. Since the nonlinearity in the SOA is relatively slow, these measurement techniques are most appropriate for picosecond pulses often found in telecommunication applications. The temporal resolution of these methods are limited by timing jitter, which was ≈0.5 ps for the mode-locked laser diodes we used in our experiments, and by the width of the switching window     

Adaptive nonlinear cancellation for high-speed fiber-optic systems

The authors propose techniques for adaptive nonlinear cancellation of intersymbol interference (ISI) in the electrical signal at the receiver in Gb/s lightwave systems and describe several demonstrations of these techniques. Techniques for adjustable nonlinear cancellations are discussed and demonstrations of these techniques using commercially available integrated circuits (ICs) at data rates as high as 1.7 Gb/s are described. Techniques for automatic adjustment are discussed, and a demonstration of adaptive nonlinear cancellation at 450 Mb/s is described. The authors discuss how these techniques can be integrated onto the detector IC for operations at 2.5 Gb/s and higher data rates. These techniques allow a single IC detector with adaptive nonlinear cancellation to be used in long-haul and undersea lightwave systems to optimize the detector threshold and compensate for the ISI     

激光触发GaAs光电导开关非线性现象的实验研究

实验研究了光电导开关的非线性现象,结果表明用半导体激光脉冲串触发光电导开关,在保持激光触发GaAs光电导开关实验条件不变的情况下,产生非线性的电阚值会不断降低.测量和比较试验前后光电导开关暗电阻,初步表明产生非线性的电阈值降低,是光电导开关因光照和产生非线性引起内部材料物理机制发生变化所致.     

Absolute measurement of the second-harmonic generation nonlinear susceptibility of tellurium at 28.0 µm

The second-harmonic generation nonlinear optical susceptibility of trigonal tellurium has been measured at 28.0 μm by the phase-matching technique. The value obtained was|d_{11}| = (5.7 pm 1.9) cdot 10^{-10}m/V in MKS units. This value establishes the longest wavelength "standard" for the measurement of nonlinear optical susceptibilities by comparative techniques. Experimental details and data are given to justify the quoted uncertainty.     

Fault diagnosis of analog circuits

In this paper, various fault location techniques in analog networks are described and compared. The emphasis is on the more recent developments in the subject. Four main approaches for fault location are addressed, examined, and illustrated using simple network examples. In particular, we consider the fault dictionary approach, the parameter identification approach, the fault verification approach, and the approximation approach. Theory and algorithms that are associated with these approaches are reviewed and problems of their practical application are identified. Associated with the fault dictionary approach we consider fault dictionary construction techniques, methods of optimum measurement selection, different fault isolation criteria, and efficient fault simulation techniques. Parameter identification techniques that either utilize linear or nonlinear systems of equations to identify all network elements are examined very thoroughly. Under fault verification techniques we discuss node-fault diagnosis, branch-fault diagnosis, subnetwork testability conditions as well as combinatorial techniques, the failure bound technique, and the network decomposition technique. For the approximation approach we consider probabilistic methods and optimization-based methods. The artificial intelligence technique and the different measures of testability are also considered. The main features of the techniques considered are summarized in a comparative table. An extensive, but not exhaustive, bibliography is provided.     

非线性动态数据协调技术

通过应用数据协调技术，可以消除或降低测量误差对过程测量数据的影响,同时可以提高过程数据的精确性和平衡性。目前，稳态线性模型的数据协调技术已得到了良好的发展并已广泛应用于实际生产过程,但实际的生产过程往往是非线性或动态的。文中的重点就是对非线性和动态数据协调技术及其发展作较为详细的阐述.     

Measurement and simulation of memory effects in predistortionlinearizers

Detrimental effects of memories in linearizers are described, and two efficient techniques are presented to measure them. These techniques allow a real-time adjustment and correction of the linearizer and/or amplifier circuits and an overall improvement of the intermodulation performance over a wide envelope frequency band. This is especially important for broadband applications, where high efficiency and linearity are required, and where memory effects, if not detected and properly corrected, may significantly degrade the system's performance. Experimental results for a 20-W linearized L-band power amplifier are presented to illustrate the effects of memory. The two techniques-a dynamic AM/AM and AM/PM measurement system and a pulse power measurement system-are described. A simulation approach that can be used to predict the influence of memory effects in practical systems is illustrated for nonlinear amplifiers. Adaptive linearization techniques are discussed     

Third order nonlinear integrated optics

The authors review progress in the application of nonlinear optical phenomena to integrated optics. Essentially all integrated optics devices such as directional couplers, Mach-Zehnder interferometers, prism couplers, etc., can be used for all-optical signal processing when at least one of the waveguiding media exhibits an intensity-dependent refractive index. Experimental and theoretical results on the operating characteristics and figures of merit of such devices, as well as a new class of phenomena based on large nonlinear changes in waveguide properties will be summarized. Also discussed are measurement techniques for evaluating waveguide nonlinearities. Progress in the implementation of other nonlinear third order interactions, such as degenerate four-wave mixing and nonlinear spectroscopy, will also be reviewed     

Considerations of accuracy in the determination of the capacitance-voltage law parameters of microwave diodes

Methods used to obtain the parameters of the C-V law of varactor diodes are considered with reference to the effects of errors including that introduced by the finite measurement signal amplitude. It is shown that commonly used graphical techniques are unsuitable where great accuracy is required and that a nonlinear least-squares technique is preferred.