2005 Vol. 26, No. 1
The optoelectronic technology, which occupies an important position in the course of the equipment modernization, is an important supporting technology of the informatized construction and the national defense industry. The importance of the optoelectronic integrated technology is described and its main research contents is summarized in this paper. Some corresponding suggestions is proposed for the development of the technology in future.
The key of THz is its generation and detection. In this paper,two methods of THz generation and detection are introduced.The imaging device,imaging mechanism and imaging process of THz technology are analyzed. The prospect of its application in biomedical are also reviewed.
Mie scattering is a generally recognized technique with brillant prospects in particle measurement,which applies to the measurement of particle size and concentration of flue-dust emitted from factories or enterprises.It has many advantages, e.g.non-contact,high-precision, real-time on-line measurement etc. It is a main technical means for research on pollutant emission. It is also a theoretical base to analyze the particle size and concentration. In this paper, several parameters of Mie scattering are calculated and its mathematical expressions are presented in detail.
The analytical expression of Jones matrix for second-order PMD of a single-mode fiber has been derived from the relation between PMD vector and Jones matrix.This matrix could be used to determine the output temporal pulse expression in a second-order PMD approximation and it is applied to simulate the impact of PMD on the quality of signal transmission.It shows that the signal will become bad with the increase of transmission velocity and distance by comparing the wave figure and eye diagram of input and output pulse. Furthermore, the influence of the second-order PMD must be considered when the rotation velocity of principal states of polarization(PSP) increases. Above results can be used to design fiber-optic communication systems when the impact of PMD needs to be considered.
The different categories of CDMA address codes and corresponding characteristics are introduced.The method of constructing a two-dimensional combined address code of time spreading/frequency hopping is given, and the characteristics of constructed address code are analyzed. In the end, the realization method of this address code is illustrated. This new code has good performances in autocorrelation, cross-correlation and capacity, and can be easily implemented by FBG and AWG. The decoder and encoder of two dimensional code are easier in selecting address and integration than those of one dimensional code.
Diffusion approximation (DA) theory is often used as basis of the experiments and methods in determining the optical properties of biological tissues. However, DA is only an approximation of the accurate radiative transfer theory and has its validity range under given conditions.In order to assess the validity of the DA under the requirement of in vivo non-invasive measurement, we compared the results from the DA theory with the more accurate results from the Monte Carlo methods.A numerical validity criterion for the DA is established on the basis of the single-scattering albedo a and anisotropy factor g for semi-infinite tissus with index-matched boundaries.
On the basis of Rytov variance, the log-intensity variance when partially coherent beam goes through strong turbulenc with Andrews model is deduced . The result shows along with the light source coherence becomes worse, that is the light becomes partially coherent light,the log-intensity variance on the receiving plane decreases. When the partially coherent light in multiple beams are used, the log-intensity variance is distinctly improved. But the transmission distance of communication is limited, when the coherence is bad. Therefor, the value of coherence parameter must be chosen properly.
At first the operating characteristics of CCD and the feature of charge formation, storage, transfer, output are analyzed. Then the modulation transfer function of CCD camera detector arrays for millilary application is derived from the array diagram of CCD detector. Finally,the quantity of the electron output of CCD detector is obtained at a certain condition with the algorithm.this is very important on the theory to analyze the performance of the optoelectronic structure.
A new method for generating Moire fringe is obtained by changing the beam path of the Mach-Zehnder interferometer. With the image collection card, images,which are detected by CCD, can be displayed on the computer for observation. The characteristics and parameters of Moire fringe are analyzed in this paper. At last the application of the new method is researched.
Considering characteristics of the cannon barrel image, a new method for image enhancement based on human eye visual property was proposed. Which can improve the observation effect on the spying bore image and diminish the target image ambiguity casued by background and noise. It is the method in which different processing is applied according to the image feature diversity between target and background-noise.In this method, the imperfect view in a image is correspondingly enhanced, and the target is thus prominent, which is convenient for human eye observation.
A fiber Bragg grating pressure sensor with high sensitivity used as the pressure underlay on thin-wall straincanister for oil down-hole is advanced. The experimental result shows that its pressuresensitivity is 1.23×10-4 MPa-1,several times higher than that of any other fiber Bragggrating sensors reported previously.
The splitting character that the reference wavelength, incident angle and the number of thin-films change with wavelength is analysised based on Macnielle type thin-film prism by using TFCALC software, which will contribute to the optimization and deposition technology of this kind of prism. We proposed a optimizing design of a polarizing beamsplitter whose substrate is LaK2 and the thin film material is ZrO2 and SiO2.
We get nanometer-sized InSb particle films deposited on the SiO2 subs trate by using vacuum evaporation. The atomic force microscopy was applied to the morphology survey of the film surfaces. The results show that the films are composite of nano-particles of InSb.With the analysis of the scanning images of these samples, the result of the experiment proves that different sizes of InSb particles can be formed by changing the plating time.
A on-line all optical-fiber fluorescence spectrum measuring system which can simultaneously measure Chlorophyll-a and b fluorescence spectrum in alga is introduced. Since wavelet transform can decompose signals into localized contributions of different frequency, it is applied to the technology of optical fiber and fluorescence methods to measure and to smooth the fluorescence spectrum of alga contained Chlorophyll-a and Chlorophyll-b. On this condition, the overlapping fluorescent peaks was resolved. It has the advantages of minitype,simple structure,passive sensing head, little spectral deformation, simultaneous multi-parameter measurement. It has been testified that this method is practicable.
The constant of grating is one of the most important parameters to assess the quality of grating.A new method to measure the constant of grating is discussed in the paper. The information of a diffractive image is captured by planar-array CCD.The constant of grating can be got by calculating the power ratio of the main facula to the ±1~astafacula.With the advantages of the quick detection, simple structure and high precision,the method can be used in real-time measurement of the quality of gratings in production process.
CCD-IT-P1 produced by Dalsa Corporation is a linear scanning CCD which has 1024 pixels, and it outputs the image signals by four channels. Many problems existing in the drive aspect are analyzed in this paper. Aiming at the technology of four channels, the high requirement of driving frequency and the complex sequence etc.,we put forward a method in which the complex programmable logic device(CPLD) and very-high-speed integrated circuit hardware description language (VHDL) is used. This method of using complex VHDL achieves the function gotten by many gate-circuits, solves the jamming of the gate-circuits, and raises the degree of integraliztion,the performance of anti-jamming and the transplant. The experiment shows that to use CPLD for driving this CCD can achieve the favorable performance.
MEMS(micro-electro-mechanical system) is a new fabricating technique, Which is widely used in the optical communication and has a great value in the communication market.The optical switch is an important passive device,which can selectively control optical signals in the optical communication of optical network system. The new type of optical switch, which is made with MEMS, has many advantages, such as small size, light weight, low consumption and high integralization. Therefore, the research on the optical switch has become an object which more and more experts are hunting for. In this paper, the MEMS and its main characteristics are briefly introduced, the application of MEMS in the optical communication thoroughly described, and the structure, the trend of development and the main problems of the MEMS optical switch are analyzed respectively.
The working principle,structure and the temperature character of a novel variable optical attenuator are intro-duced in this paper. We can obtain the character curve of the variation of novel variable optical attenuator's insertion loss with temperature by using the on-line temperature test.In the end we propose an idea of improving the optical attenuator's temperature stabilization by optimizing the processing technology.