A cost-effective ultra-dense WDM PON system with speed of 12.5 Gbit/s and channel spacing of 12.5 GHz

In this paper, an experimental scheme for cordwood color division multiplexing（CDM） visible light communication（VLC） system is proposed. The principle and structure of the experimental scheme are described. Right angle prisms and band-pass filter are used to make the unit of the optical collector and splitter. We can add or subtract the unit as we need. The cordwood CDM-VLC system can also be effectively used as a model to accomplish color shift keying and color division duplexing. The experimental system provides a new way for researching VLC.     

Detection of dynamic strain using an SOA-fiber ring laser and an arrayed waveguide grating demodulator

In this letter, a fiber Bragg grating (FBG) dynamic strain sensing system using a semiconductor optical amplifier (SOA)-fiber ring laser (FRL) and an arrayed waveguide grating (AWG) demodulator is proposed. Due to the characteristics of SOA, it can act as the gain medium as well as light source. The AWG module is used as the wavelength demodulator. It is shown that SOA-based FRL sensors can accurately respond to 1.5 με dynamic strain signal with high frequency up to 120 kHz and almost no distortion in the waveforms. Experimental results show that the system can be used for acoustic testing, such as underwater ultrasonic detection and external impact monitoring. In addition, the simultaneous dual-channel demodulated system is investigated in detail to verify the multiplexing. This dynamic strain sensing system can be widely utilized in structural health monitoring because of its high stability, low cost and good multiplexability.     

Features and Prototypes of HTS High Q Resonant Circuit

High Te superconductor （HTS） technology has been used to develop a unique high Q resonant circuit. Such circuit or device has some special characteristics such as very high voltage generation. Theoretical study and experimental approaches have proceeded for the concept verification. This paper presents the theory about this high Q resonant circuit. The operation principle of the circuit is described. A practical prototype for HTS high voltage generation is also demonstrated. The experiment result shows that very high voltages can be achieved by the developed method using HTS technology.     

NEDI''''JW20012 11GHz Microwave Communication System

<正>The 11 GHz microwave communication unit designed and manufactured by Nanjing Electronic Devices Institute can mainly be used in harbour traffic control systems. It transmits informations of the radar, meteorology, telemetry and image from radar stations outside the harbour to the control center. It can also be used in analog and digital communication systems.The microwave communication system is constructed of two subsystems:receiver and trasmitter. The receiver is composed of low-noise amplifier, mixer-intemediatc-preamplifier,dielectric resonator local oscillator and intermediate frequency module,and the transmitter is composed of frequency upconverter,dielectric resonator local oscillator and FET power amplifier. The system is featured by complete solid state,low power consumption, high receiving sensitivity, high transmitting power and high reliability. Some important specifications are as     

Design of atmospheric composition monitor based on ultraviolet optical absorption technology

An open path atmospheric composition monitor is designed based on ultraviolet differential absorption technology.Dark current correction and diode response correction are used to improve the detection limit and Savitzky-Golay filter is used to improve the measurement accuracy.The experimental results show that the designed system has the ability to measure NO and NO 2 in real time with reasonable accuracy.The detection limit of the system is about 0.25 ppm for NO and 0.28 ppm for NO 2 .When the concentration level of the target gases is below 100 ppm,the system has good linearity and high measurement accuracy,i.e.,the measurement accuracy is about 2%for NO and about 4%for NO 2 .The detection limit of dark current can be improved by about 5 to 10 ppb,and the correction of diode response can improve the detection limit by around 30 ppb.Moving window average can improve the detection limit at low concentration levels but will generate more errors at higher concentration levels.Generally,the designed system meets the requirement of measuring multi-species air pollutants in real time and accurately.     

Two—color Optical Fiber Pyrometer

On the basis of thermal radiation from solid surface to measeure tem-perature,a new two-color optical fiber pyrometer is put forward.It gets two thermal radiation signals by the method of Y-type optical fiber and narrow band filter for indi-cation of the temperature,Si diode in used for photoelectric measurement and MCS-51 single-chip microcomputer for sampling and handling.The system can output in digital and can print out instantaneous value,peak value and valley,It has many advan-tages such as quick measurement,small objective,high precision,high sensitivity and non-emissivity compensation.in addition,the special circuit of this pyrometer and the es-tablishment of mathematics model are discussed.     

All-optical switching in 3,3′-diethyl-2,2′-thiatricarbocyanine Iodide dye molecules

All-optical switching has been theoretically analyzed in the 3,3＇-diethyl-2,2＇-thiatricarboeyanine iodide （DTTCI） carbocyanine dye that exhibits large excited-state absorption to achieve high contrast and fast switching. Switching has been analyzed both ns and ps pump pulse widths. It is shown that there is an optimum value of concentration for given peak pump intensity at which maximum modulation can be achieved. We can get 93.84% modulation of transmission of a CW probe laser beam at 532 nm at peak pumping intensity of 500 kW/cm^2 at 763 nm, with At =1 ns and concentration of 80 μM in alcohol, resulting in switch-off and on time of 2 ns and 8 ns, respectively. The results have been also used to design all-optical NOT and the universal NOR and NAND logic gates with multiple pump laser pulses.     

TURBO TRELLIS CODE MODULATION USING MQAM

The paper presents a kind of reasonable structure for implementing MQAMT-TCM based on the principles of turbo codes and TCM for the first time.It can also be expanded to PSK T-TCM system,and the corresponding decoding algorithm is derived .By computer simulation,its performance is analyzed .The results show that T-TCM takes the advantages of turbo codes and TCM technology,and is a kind of bandwisth-efficient coded-modulation technique obtaining high coding gain .So,in the future,T-TCM would be applied in many fields.     

Application of CCD Technique to Stress and Strain Measurements of Metals

Crossed grating stuck to metal surface was used as a strain sensor in the present work,and stress as well as strain were then investigated by accurately determining the change in the position of diffraction spot before and after deformed.A hardware testing system for linear CCD array,data gathering and processing was therefore developed for this purpose.Experimental results showed that the system has a good accuracy and can be used to measure stress and strain of metal surface in a real-time and quantitative manner.     

Measurement of Moisture Inside the Hermetic Package of Semiconductor Device

The mositure content inside the hermetic package of semiconductor de-vice has been quantitatively measured by using in-site sensor technique and computer-aided-test system.The principle and apparatus for measurement are introduced.The results show good repeatability and consistency.This technology can be used as a stan-dard test for controlling the moisture content within semiconductor device package.     

光纤荧光式测水中矿物油浓度

石油污染已经成为我国水域环境的主要问题之一,为了掌握石油污染的动态变化趋势,需实时在线测量水中石油浓度。从荧光测量的基本原理出发,研究了水中矿物油荧光检测机理、用荧光法和全光纤传感技术实现石油浓度测量的可行性,建立了水中油浓度的测算模型,确定了其荧光检测的最佳激发波长和荧光波长范围,根据得到的荧光特性设计了荧光激发、吸收和传输的光学系统。选用氙灯作为激发光源,设计了相应的检测系统及放大电路,通过以单片机为控制核心的高速数据采集电路实现了信号的采集转换,最后将数据输入计算机,处理得到了相应的石油荧光光谱。该方法可广泛应用于水中油检测方面。     

1.064μm激光在海水中传输特性的研究

为了实现激光雷达监测海洋赤潮的目的,采用红外激光能较好地反映藻类悬浮粒子密度等信息.分别就海水中水分子、浮游植物、黄色物质、悬浮颗粒与1.064μm激光的吸收和散射特性展开研究,最终构建了1.064μm激光在海水中的探测模型.通过对模型的仿真计算可知,红外激光雷达能有效地探测水下0.8m内的海水水域.结果表明,1.064μm激光水下探测深度可满足监测海洋表层藻类粒子密度的要求.     

Novel Fiber Optic Fluorometer for the Measurement of Alga Concentration

A novel flurometer base on fiber optics is briefly introduced for the measurement of alga concentration.Both the exciting light and the fluorescence form alga chlorophyll are transmitted along a fiber cable.By this way.we can get alga concentration by measuring its chlorophyll-a fluorescence intensity.The experiment results show that this instrument is characterized by good sensitivity,linearity and accuracy.     

Nd:YAG激光器在柴油机喷雾测量中的应用

开发出了一套使用532 nm Nd:YAG激光器作为激光源,用于柴油喷雾浓度及粒径测量的测试系统,具有测量环节少,精度高,可以测量真实柴油喷雾的特点;使用该系统,获得了柴油撞壁喷雾的浓度及粒径分布图,发现了喷雾内部存在拟序结构.     

Theoretical analysis of the layer design of inverted single-channel heterostructure transistors

In this paper the inverted heterostructure transistor is analyzed using a self-consistent model for calculation of the electron concentration and spatial distribution in the quantum well. The (In,Ga)As/(Al,Ga) As material system is considered in particular. The objective of the study is to design a transistor with a high channel electron concentration and a short gate-to-channel distance. It furthermore is desired that the channel concentration can be selected without influence from the gate-to-channel distance. Placing the gate close to the channel means that the leakage current may become unacceptably high. The analysis therefore includes an estimate of the leakage current that can be expected for each structure. It is shown that the best way of meeting the design objectives is to use a material between the channel and the gate, which consists of two layers with low- and high-bandgap materials, respectively. The structure will thus consist of a potential well with the electron accumulation occurring at the lower interface. The lower high-bandgap material furthermore should be doped as high as possible. The upper limit for the doping level in the topmost layer is determined by the maximum acceptable gate leakage as well as by gate-drain breakdown. (The latter also being partly determined by the device contact geometry.) Governed by the restrictions imposed by the application of the transistor, the model can thus be used to optimize the layer design for, e.g., minimum noise figures.     

The Hat Creek millimeter-wave interferometer

A fixed-baseline millimeter-wave interferometer, operating initially at 13.5 mm, has been put into operation at the Hat Creek Observatory as the first step in the development of a two-element aperture synthesis telescope. The first system consists of a 3-m antenna and a 6-m antenna spaced 265 m apart. Large receiver bandwidths may be used at high frequencies, and this system employs an intermediate frequency bandwidth of about 400 MHz. It also has automatic gain control and a phase stabilized local-oscillator reference cable. Observations may be made either in the continuum or with a 128-channel spectrometer. The baseline vector has been obtained from observations of about 7 QSO's. The instrument has been used to derive accurate absolute positions of interstellar water vapor sources, to study Mercury, Venus, and Mars, and to make crude maps of a few complex continuum sources. Measurements of the interferometer phase fluctuations due to the atmosphere indicate that interferometer is possible under average weather conditions at Hat Creek at wavelengths as short as 2 mm. The synthesis telescope, the next stage, has two 6-m antennas which can be located at various stations on a T-shaped track. The east-west leg is 300 m and the north-south leg is 200 m, permitting full synthesis for sources on the equator and at declinations as low as -30° as well as at high declinations. Operation at wavelengths down to 2 mm will be possible with resolution of 1"-2".     

基于光声光谱法的光纤气体传感器研究

论述了光声光谱信号的产生。提出用光纤相位传感器代替传统的微音器检测光声信号 ,讨论了光纤中光波的相位变化与光声信号的关系。设计了光学长程结构 ,有效增加了对光功率的吸收。用染料激光器作光源对SO2气体浓度进行测量。实验表明 ,最低检测灵敏度可达 1 2× 10 -10 。由于采用光谱技术与光纤技术相结合 ,使研制的传感器具有较高的灵敏度 ,信号的传输通道具有强的抗电磁干扰及防燃防爆能力。气体探头体积小 ,响应速度较快。信号处理电路具有较强的抑制噪声干扰能力。该传感器及其系统在灵敏度、精度、响应时间等性能指标上达到了检测气体含量要求     

固相微萃取-气相色谱三重四极杆质谱对自来水中卤代烃类消毒副产物的检测

利用固相微萃取-气相色谱三重四极杆质谱技术(SPME-GC-TQMS)对合肥市科学岛不同区域自来水进行了检测,研究了该地区自来水中部分消毒副产物(DBPs)的存在情况,以及DBPs含量与自来水封存时间的关系,并利用SPME-GC-TQMS对煮沸的自来水进行检测,考察煮沸方式去除卤代烃类消毒副产物的有效性。结果表明: 科学岛自来水中存在三氯甲烷、一溴二氯甲烷和二溴一氯甲烷等多种卤代烃类DBPs,且来源于不同建筑物的自来水中DBPs含量差异高达3倍;自来水在水管内存储时间越长,卤代烃类DBPs浓度越低;自来水经过煮沸处理后,大多数卤代烃DBPs可有效去除,但三氯甲烷仅降为原自来水中含量的30.2%,仍大量存在于凉开水中。     

A novel method to obtain modulus image of soft tissues using ultrasound water jet indentation: a phantom study

The alteration of tissue stiffness is generally known to be associated with pathological changes. Ultrasound indentation is one of the methods that can be used to assess the mechanical properties of the soft tissues. It uses a flat-ended ultrasound transducer to directly contact the tissue to sense tissue deformation under an applied load. This paper introduced a novel noncontact ultrasound indentation system using water jet compression. The key idea was to utilize a water jet as the indenter as well as the coupling medium for propagation of the ultrasound beam. High frequency focused ultrasound (20 MHz) was used to measure the indentation deformation at a microscopic level. It has been demonstrated that the system could effectively assess the tissue-mimic phantoms with different stiffness. Water jet coupling allows the system to conduct C-scan on soft tissues rapidly and conveniently. By applying different pressures while taking C-scan sequences, the modulus images of the phantoms could be obtained based on the applied pressure and the phantom deformation and thickness. This paper presented the preliminary results on gel phantoms. The spatial resolution, the contrast resolution of the measurements and the reproducibility of the results were also discussed.     

Novel photoresist stripping technology using ozone/vaporized water mixture

The authors have developed a new process as an alternative to sulfuric peroxide mixture (SPM) cleaning of Si wafers. This process, vapor ozone strip (VOS), uses ozone and vaporized water, significantly reducing any effect on environment, health and safety. The process is more effective than ozone water immersion, because high concentration ozone gas and high temperature water can be used simultaneously. Also, the process uses the highly reactive OH* radical species. The VOS process is able to strip photoresist at a higher rate than other techniques using ozone. Ion implanted photoresist and etched photoresist can be stripped. VOS has demonstrated equivalent performance to SPM in electrical reliability testing.