2004 Vol. 25, No. 3
Power and energy is the two basic parameters for laser, the measurement for these two parameters is the most basic work for laser parameter metrology. We summarize the status quo of NIST of America,NPL of England and NIM of China,and show in detail the specification our Optic Metrology Station has possessed, which include the measurement theory, measurement range and measurement uncertainty. The development direction for laser power and energy metrology is given in the end.
In that paper,I expatiated on the course of development and status quo of SIPOF and GIPOF at home and abroad,and introduced the application in LAN,CAN and OFS.As a guided-wave media,plastic optical fiber(POF) has gained an increasing attention in the world for its unexampled merits(easy fabrication, low cost, high plasticity and so on), comparing with silicon optical fiber and cable.Applications of POF in LAN,CAN and OFS were analyzed and summarized.The result indicates that applications of POF are limited by its transmission loss. The advice for how to raise the technical level of POF in China was brought forward at the end of the paper.
Tellurite glass doped rare earth is a kind of important material used in fabricating broadband fiber amplifiers. It has the properties of wide transmission region, good stability and so on. We discussed the radiative lifetimes of rare earth ions(Pr~(3+),Er~(3+)) in tellurite glasses while the diode-pumped laser is at 980nm. We selected a 100MHz digital oscilloscope to monitor the fluorescence decay in the radiative lifetime measurement and calculated the radiative lifetime with the dacay data obtained from the oscilloscope through the fitting calculation of the least square method.
By way of overcoming mechanism structure factors seriously affecting on performance of opto-electronic tracker servo systems, the relationship between servo system performance and servo mechanism structure factors that consist of inertia moment,structure resonance frequency and friction moment is analyzed. These include relations between inertia moment and servo system performance, between structure resonance frequency and servo system performance, and between friction moment and servo system performance. The measures that avoid or minimize the mechanism resonance are probed. These analytical methods may be used to design and make the opto-electronic tracker servo systems with quick response and high tracking accuracy.
The phenomena of light scattering often occur in the natural environment.The Mie scattering theory, which is derived from the Maxwell equations,exactly represents the distribution of scattered light. The refractive index of mediums is directly related to the distribution of scattered light. And it is very important to carry out a qualitative analysis and a quantitative analysis. In this paper, by means of experimentations and numerical analyses, it is confirmed that the real part variation of the refractive index of mediums influences the distribution of irradiance intensity less than the imaginary. This result can be used for many studies which base on the distribution of scattered light.
In this paper,we present a new project for semiconductor optical amplifiers(SOA),in which Gaussian signal pulse can be compressed by using the rectangular control pulse. Numerical simulation results show that the width of Gaussian signal pulse can be strongly compressed by utilizing the rectangular control pulse. Under this situation, a stable peak power of the signal pulse can still be obtained by Matlab software.
A novel least squares algorithm based on anti-WKB method and linear segment interpolation,which is called prediction-verification method, is proposed.This method takes the values calculated by anti-WKB and linear segment interpolation as approximation(prediction),then uses the least squares fitting (verification),and after that compares the linear segment interpolation based on the anti-WKB method with it. Numerical results show that the prediction-verification algorithm can effectively reconstruct the transverse refractive index profile of graded ion-exchange planar waveguide.
The relation of ray axis and optical axis is discussed by using the optical wave camber of biaxial crystal. The mathematical expression of included angle between ray axis and optical axis is also given. The result shows that the included angle is much less than 1° in two biaxial crystals (topaz and cordierite). This is important for the design of the optical devices. It indicates that the direction of ray axis and optical axis is identical by discussing the uniaxial crystal at last.
CRT digital color printer is a high-technique product developed in recent years, which deals with optics, mechanics, electronics and computer technology. It consists of four main parts, which are called main computer system, optical system, electronic-control system and color printing system. The optical system is a projective optical system with long focus and large field of view,and is an important part of the equipment. The feature, difficulty and result of the design of the optical system are figured out in this paper.
A modulated laser interferometer used for piezoelectric characteristic measurement of the piezoelectric ceramic is discussed. By this method, it can not only suppress the effect of noises on the interference signal, but also adequately reduce the effect of so called 1/f noise of the photo-detector and electric elements. Compared with general interferometric method, the modulation interferometry has an advantage of high precision. Finally, the piezoelectric constant d31 of a piezoelectric ceramic versus the frequency and amplitude of the excited voltages,and the hysteresis loop of the material are measured with this method.
Laser measurement based on triangulation is a traditional method for measuring displacement. Along with the development of Lasers, photoelectric detectors and computers, triangulation method has made much progress and found more and more applications. Several laser methods based on triangulation for measuring displacement are surveyed and discussed in this paper. Laser triangulation measurement techniques can be mainly divided into two types,the normal incidence and oblique incidence, based on the incidence way of the light.The measurement principles of these two kinds are introduced respectively and their characteristics are compared. Some application examples and the development trends of high precision laser displacement sensor based on triangulation are given at the end of this paper.
In this paper lamp pumping and diode pumping for solid-state lasers are compared. The different forms of pumping for different sorts of solid-state lasers are analyzed in details. It is the conclusion that the diode pumped solid-state lasers are the main trend of the future development of solid-state lasers.
The methodology of real time image processing of near-infrared rail abrasion detection system has been studied. In consideration of accurate abrasion value,the location of starting point is very important. For this, two feasible location methods have been offered. One of the two methods has been put into practice. And the results are in line with the actual abrasion values. In addition, the key technology of the extraction of reflection-streak center line has been discussed. For more,Roberts edge detection has been applied and the single-pixel center line is extracted. The method got a good effect and their processing speed is fast,which show that it can meet the demand for real time cross-section detection system.
Fiber-optic communication has been growing at a phenomenal pace over the past twenty years, so rapidly,in fact, that its impact is increasingly felt in nearly all aspects of communication technology.Transmission properties of tapered fiber are discussed in this paper.The transmission efficiency of the tapered fiber is measured. By the scalar wave equation and Gaussian approximation,transmission properties of tapered fiber are analyzed, and the power losses caused by taper angle are also calculated. The distribution of power in the fiber versus the normalized frequency, the spot size versus the core diameter, the data sheet of transmission efficiency with coning angle, and the transmission efficiency T versus the tip diameter are all discussed in this paper. According to a sequence of coning angle,the curve of transmission efficiency versus coning angle is given. From the experiments and analyses, it could come to the conclusion that the bigger the taper angle is, the higher the transmission efficiency becomes.
Flufenoxuron has very high insecticidal and ovicidal activity. It can prevent coleoptera, diptera and lepidoptera injurious insects from damaging maize, cotton, fruit, vegetable and soybean. It has been used in a great quantity for its characteristic of quick results, but can cause soil and water resource pollution. Therefore, it has an important value to monitor its concentration and develop monitoring instrument.Based on the mechanism that flufenoxuron can emit fluorescence in the ultraviolet light, a fluorescence fiber-optical measuring system is developed for monitoring its concentration. This system makes use of high-pressure mercury lamp as exciting light source. It combines with fiber-optical sensing technology to realize precise measurement of the concentration of flufenoxuron. Using this system to measure flufenoxuron's standard solutions,the fluorescence intensity has a linear relationship with the concentration in the concentration range of 0.050～1.000μg/ml.Because almost all the benzoyl urea pesticides(hexaflumuron and triflumuron,etc)by changing exciting and emitting filters and system configuration parameters.This fluorescence fiber-optical measuring system for measuring the concentration of benzoyl urea pesticides has several characteristics such as high sensitivity,wide linear range and low cost,etc.This research has established a good base for further improving the capability of domestic pollution detection and developing actual application of environment monitoring instruments.
Recently, the on-line measurement technique using CCD image is widely used. This paper presents an on-line image measurement method that can be used to measure the diameter of glass rod. Firstly,the images are obtained by CCD capturing. Secondly, based on the characteristics of the image, the image edge of the glass rod is detected. Then the sub-pixel edge detection method is used to determine the edges accurately. Lastly, the beeline fitting method is used to obtain the diameter of the glass rod. The method not only can substitute traditional manual measurement, but also can control the change of the diameter by machine conveniently. The experiment shows that the method can obtain good result.
Ka-band coupled-cavity traveling wave tube amplifiers have been developed for military radar application requiring high power, moderate bandwidth and light weight.The design features and measured performance characteristics of these devices are presented and the basic components of TWT are illustrated. The technology advancement achieved in the radar programs is being leveraged to design Ka-band amplifiers that surpass power limitation of existing solid state or helix TWT systems. The Ka-band coupled-cavity TWT technology has demonstrated output power, bandwidth and weight advantages in high-resolution military radar application.
Proceeding from the sensitivity improvement,the relation between the electrode length and the sensitivity/bandwidth of no-electrode electrical field sensor is analyzed. By comparing the transmission function of different structures and verifying the feasibility of balanced detection scheme, the 3-port structure using balanced detection is chosen for the coming generation sensors.