Analytical and numerical analysis of phase and amplitude errors in the performance of arrayed waveguide gratings

The closed expression of the mean power transfer function for an arrayed waveguide grating (AWG), taking into account fabrication errors, is presented. Comparison with numerical simulations using a previous Fourier optics modeling show good agreement. The procedure to predict the AWG floor level using the numerical modeling is presented and checked against the analytical derived expressions.     

Semiconductor arrayed waveguide gratings for photonic integrated devices

This paper reviews recent progress of the semiconductor arrayed waveguide gratings (AWGs) and the integrated semiconductor optical devices including the semiconductor AWGs. Recent research enables us to make semiconductor AWGs with sufficiently low insertion loss and polarization dependence. Using the semiconductor AWGs as core components, the integrated semiconductor optical devices are developing by integrating with the other semiconductor devices including photodetectors, optical amplifiers, and electroabsorption modulators.     

N/spl times/N arrayed waveguide gratings with improved frequency accuracy

The limitations imposed by the frequency standards on the performance of N/spl times/N arrayed waveguide gratings (AWGs) are reviewed for different device layouts. An improved design that allows for an enhanced frequency accuracy of the transmission response of the device is presented and experimentally verified. The maximum deviation from the frequency standards is reduced by almost a factor of two in a 32 /spl times/ 32 AWG with 100 GHz channel spacing.     

Calculation of dispersion in arrayed waveguide grating demultiplexers by a shifting-image method

It is shown that, as a first approximation, chromatic dispersion in demultiplexers based on arrayed waveguide gratings (AWGs) is proportional to the local spatial curvature of the wavefronts of the field at the output of the input guide, whose image shifts across the output guide as frequency changes. More accurate results can be obtained by convolving the input field with the AWG impulse response and the output guide mode. This approach to the calculation of dispersion provides physical insights from the field of imaging, not available with the commonly used method which relies on a Fourier series approach. Spherical wavefronts lead to constant dispersion. The use of a parabolic taper at the end of the input guide can lead to large amounts of dispersion, varying across the filter passband; this case is treated in detail. The method can also be adapted for use with demultiplexers based on reflective echelle gratings.     

Characteristics of polymer waveguide notch filters using thermooptic long-period gratings

We demonstrate experimentally the feasibility of a polymer waveguide notch filter using a thermooptic long-period grating. This notch filter consists of a channel waveguide, a cladding surrounding the channel, and buffer layers sandwiching the cladding. Periodic heaters formed on the upper buffer layer induce a long-period grating thermooptically. Thus, they generate temporarily a resonance band of notch type in the transmission spectrum of the filter. Using thermocurable polymers, we have fabricated notch filters 1 and 2 that have different cladding thicknesses. Experimental results demonstrate two features of the notch filters. One feature is dynamical controllability of the attenuation of a resonance band. For TE mode, the maximum attenuation of notch filters 1 and 2 increases from 0 to 27 dB as the power applied to notch filters 1 and 2 increases from 0 to 851 and 1170 mW, respectively. The other feature is controllability of the direction and magnitude of the center wavelength shift occurring when the attenuation is tuned. The shift property depends on the cladding thickness. The measured characteristics of notch filters 1 and 2 are qualitatively in good agreement with our theoretical analysis. Using this feature, we may implement the notch filter whose attenuation is adjustable without center wavelength shift. This polymer waveguide notch filter may be used to implement a compact filter whose spectrum is dynamically tailored.     

Optical delay line based on arrayed waveguide gratings' spectral periodicity and dispersive media for antenna beamforming applications

An optical delay line (ODL) based on the free spectral range periodicity of arrayed waveguide gratings (AWGs) and dispersive media is analyzed with emphasis on the AWG physical features that limit its performance as a photonic antenna beamforming network. This ODL presents multiple simultaneous true-time delay, straightforward multibeam capability and a drastic cost reduction in comparison with previously reported schemes. Moreover, a simulation model of the ODL that takes into account the AWG frequency misalignment is presented. Finally, experimental results are also provided for 40-GHz electrical signals.     

Arrayed waveguide gratings, fiber Bragg gratings, and photonic crystals: an isomorphic Fourier transform light propagation analysis

In this paper, we present a unified Fourier transform (FT) approach to the study of arrayed waveguide grating (AWG), fiber Bragg grating (FBG), and photonic crystal (PC) devices. This methodology allows the design characteristics of transverse (AWG) geometries to be mapped on to longitudinal (or distributed) FBG and PC structures, due to a comprehensive isomorphism between these important passive optical grating-based devices. The unified approach presented here, which is based upon a modified Debye-Waller approach to the analytical solution of the coupled-mode equations, allows intuitive, yet accurate appraisal of arbitrary strength coupled structures. Exploiting this isomorphism, we relate our theoretical work to a number of practical cases. For example, we describe an FBG carousel configuration (analogous to a chirped AWG cascade) offering virtually ripple-free third-order dispersion compensation of 6.61 ps/nm/sup 2/ over a 100-GHz bandwidth.     

SIR测量误差对内环功控影响情况的分析

在闭环功率控制中,终端对下行链路的测量是对基站进行下行功控的基础,测量的准确性和及时性将对网络性能造成直接的影响.文中首先分析测量误差和时延产生的原因和量级,进而基于线性的功控模型,给出了测量误差和功控误差的计算方法,并得到链路BER解析式,最后分析了网络容量受影响的情况.仿真结果表明,测量误差标准差大于4 dB,时延对功控误差没有影响;大于10 dB,时延对链路性能和系统容量没有影响.要保证系统有较好的质量和容量,应将测量误差标准差控制在1 dB以内.因此,加强对入网终端测量能力的把控,对于提升网络整体性能将有积极的意义.     

Statistical analysis of correlated phase error in transmission characteristics of arrayed-waveguide gratings

Transmission characteristics of arrayed waveguide gratings (AWGs) are significantly influenced by phase errors in a waveguide array, which are easily caused by the variation of fabrication process. In this paper, the statistical analysis of transmission characteristics is presented using correlation and spectral density of phase errors. A simple statistical approach, based on a simplified model of a waveguide array, is newly introduced to clarify statistical behavior of phase errors in AWGs. Spectral density is modeled from measured phase errors, and then average transmission characteristics are simulated for AWGs with different channel spacing. Average transmission characteristics, simulated with the spectral density model, almost describe measured results in the cases of various channel spacing. It is also indicated that an AWG may have larger adjacent-channel crosstalk with narrower channel spacing because the adjacent-channel crosstalk is affected by phase errors with a smaller spatial frequency.     

温州浅滩二期围涂开发对瓯江河口演变的影响分析

围涂开发势必改变河口水域的潮流动力条件,系统分析围涂开发对河口冲淤演变的影响,能为工程的科学决策提供有力的技术支撑.本文介绍了温州浅滩泥沙淤积环境特性,分析了温州浅滩二期围涂开发对瓯江河口冲淤演变的影响.研究表明:温州浅滩的走向与瓯江南、北口潮流的主方向基本一致,围涂开发将局部改变河口的潮流动力,不会强制改变瓯江河口潮流的动力轴线,不会引起其潮流结构的总体调整,围涂开发符合河口自身演变规律;同时,温州浅滩二期围涂区域总体呈冲淤动态平衡状态,开发应采取必要的工程促淤措施,防止局部冲刷的不利影响.     

铅酸蓄电池检测误差的分析

以铅酸蓄电池20小时率容量试验为例,通过对由仪器的精度、量程的选择、试验环境、检测人员的习惯产生的误差进行分析,提出了准确掌握和处理检测误差的方法,可使试验数据更加贴近真值,增加检测的可信度。     

The impact of vehicle-to-grid on the distribution grid

Plug-in hybrid electric vehicles (PHEVs) can be connected to the power grid. The power flow of this connection can be bidirectional, so vehicles can charge and discharge. This vehicle-to-grid option can aid to improve grid efficiency and reliability. A simulation covering an entire day is essential to obtain an accurate assessment of the impact of PHEVs. It is important to know when, statistically, vehicles are available for charging or discharging. In this work is shown that uncoordinated charging of PHEVs in distribution grid can lead to local grid problems. Therefore, coordinated charging and discharging is investigated and a voltage constraint is implemented. These vehicles can support the grid in terms of voltage control and congestion management. In that way, the distribution grid can handle more PHEVs without reinforcements. Distributed generation units are more common nowadays in the distribution grid with some of these generation units based on intermittent renewable resources. This paper shows that there could be a good combination with PHEVs as they can provide storage to take care of the excess of produced energy and use it for driving or release it into the grid at a later time. In that way, consumption and generation are more efficiently matched.     

The impact of loss of control on movement BCIs

Brain-computer interfaces (BCIs) are known to suffer from spontaneous changes in the brain activity. If changes in the mental state of the user are reflected in the brain signals used for control, the behavior of a BCI is directly influenced by these states. We investigate the influence of a state of loss of control in a variant of Pacman on the performance of BCIs based on motor control. To study the effect a temporal loss of control has on the BCI performance, BCI classifiers were trained on electroencephalography (EEG) recorded during the normal control condition, and the classification performance on segments of EEG from the normal and loss of control condition was compared. Classifiers based on event-related desynchronization unexpectedly performed significantly better during the loss of control condition; for the event-related potential classifiers there was no significant difference in performance.     

The impact of the induction motor on short-circuit current

Simplified analytical models for calculation of the induction motor's short-circuit current are presented. Laboratory tests have been performed on two induction motors with low power rating, 26 kW and 122 kW, respectively, in order to measure their short-circuit current. Results calculated according to the available literature have been compared to those acquired by testing. Calculations have also been made for a high-voltage induction motor rated 1250 kW, whose parameters have been known     

The OSHA Hazard Communication Standards impact on cables

Since regulators have begun to consider acetophenone as toxic or hazardous, manufacturers and users of products containing this chemical must review its impact on their compliance programs, particularly the Hazard Communication Standard. Electrical wire and cable containing acetophenone can no longer be considered an “Article” exempt from the Hazard Communication Standard. Therefore, manufacturers of electrical wire and cable must now issue material safety data sheets (MSDSs) for any wire and cable product containing acetophenone in order to comply which federal regulations. Electrical distributors, who are subject to OSHA requirements, must add the MSDSs for these products into their existing Hazard Communication Program or institute such a program. The electrical distributors must also provide copies of the Manufacturer's MSDSs to the end user as required under the law. Industrial and commercial users of these wire and cable produces must add the MSDSs for these products into their Hazard Communication Programs at each facility. They must also provide the MSDSs with scrap or obsolete wire and cable sent to metal reclaimers     

The far-reaching impact of bioterrorism

Deliberate releases of biological agents to cause harm are now a reality. The bioterrorism attacks in the United States have affected Europe through the fear and false alarms they have generated. The member states of the European Union, working with the European Commission, are improving their planning and coordination to cope with deliberate releases of biological, chemical, and radiological agents designed to damage health. In this endeavour they are drawing from the lessons learned in the United States and cooperate closely not only with the United States but also with Canada, Japan, Mexico, and other countries, as well as the WHO. Health authorities and health services are in the forefront of this effort     

The impact of modern telecommunications

A broad overview is provided of telecommunications in developing countries. The role that basic telecommunications services play in development is examined, and the gap between availability and demand is discussed. Constraints on the growth and performance of telecommunications services in developing countries are considered. They are attributed to three interrelated factors: a shortage of investment capital, ineffective organization and management of the operating entities, and inadequate sector policies. New pressures on (and new opportunities for) developing countries to improve efficiency and quality and expand and innovate telecommunications services are addressed     

The impact of system grounding practices on generator fault damage

Industry has become aware of the problem of severe generator damage due to stator ground faults. It has been suggested that, to prevent this damage, the practices employed for neutral grounding should be changed. This paper provides an analytical perspective on this problem and suggests that the real issue is the manner in which the neutral of the generator itself is grounded     

The impact of a simulation-based learning design project on studentlearning

This study examined the effects of a sophisticated simulation-based task on students' learning of course-related content, ability to deal with complex, open-ended problems, and attitudes toward the Interactive Site Investigation Software (ISIS) and the course. Students were required to conduct a hazardous waste site investigation using the simulation software designed specifically for the course. ISIS simulated physical processes as well as real-world engineering processes. Assessment of student outcomes was based on the use of constructed-response knowledge maps to measure content understanding, and surveys to measure student attitudes and use of cognitive processes. Students reported very positive attitudes toward the ISIS experience, appeared to have gained substantial knowledge over the course of ISIS use, and perceived the ISIS activity as being generally effective in improving their skills in dealing with complex projects, linking theory to real world applications, and improving their problem-solving performance. Our assessment of student outcomes was a successful first attempt, but more work is needed to validate our measures with advanced students, particularly when the task is complex and requires interdisciplinary knowledge     

基于LCIA的洗碗机多目标环境影响评价

引入多目标评价的思想,利用AHP(层次分析)方法对洗碗机生命周期环境影响进行评价。突破了传统的只注重危害性(单位环境影响负荷)单一目标的评价方法,综合考虑各环境影响类型的危害性目标及处理难易程度目标。在设计阶段,应遵循危害大且难于处理的环境影响应最优先考虑(比如温室气体),危害小且易于处理的环境影响应最少考虑的原则,通过AHP方法对一款典型洗碗机的各环境影响进行综合评价,最终得出该款洗碗机各环境影响综合重要度排序及总的综合环境影响指数,以支持设计阶段的方案选择。