外文翻譯--用光纖布拉格光柵的三維熱膨脹系數(shù)測量鈹（原文）

1、Measurement of the three-dimensional thermal expansion coefficients of Beryllium using fiber Bragg grating sensors Xiujuan Yu1,2*, Youlong Yu1,3, Baojin Peng2,4,Min Zhang2,Yanbiao Liao2,Shurong Lai2 1 Research Institute

2、 of Fiber Optics, HeiLongjiang University , Harbin, P.R. China; 2Department of Electronics Engineering,Tsinghua University, Beijing,P.R. China; 3Institute of Opto-electronical Engineering,Jinan University,Guangzhou,P.R.

3、 China; 4Institute of Optical Information, ZheJiang Normal University, Zhejiang,P.R.China. ABSTRACT Fiber Bragg grating is simple, intrinsic sensing elements which can be photo-inscribed into a silica fiber. It has many

4、 advantages and be useful for a variety of application. In this paper, we reported the experimental results of measuring the three-dimensional thermal expansion coefficients of Beryllium by using fiber Bragg grating (F

5、BG) sensors within a large temperature range between -50and +150 . Three FBG sensors were bonded on the surface of the material in the ℃ ℃ directions of x, y, z to measure the three-dimensional thermal expansion coeffi

6、cients and a reference FBG sensor was used to compensate the temperature variation. The experimental results show that it can be used in harsh environment. Key words: Fiber Bragg grating sensor, thermal expansion coeffi

7、cient, three-dimensional, temperature 1. INTRODUCTION Thermal expansion coefficient is one of the important parameters of materials. A number of conventional electrical methods for measuring the thermal expansion coeff

8、icient have been reported [1, 2, 3], such as the use of electric resistance stain gauge, charge-coupled device(CCD) method, string wire etc. However, such methods are not suitable for measuring the one-dimensional ther

9、mal expansion coefficient in harsh environment when the temperature is ultra low and the sensors are easily influenced by the temperature and not immune to electromagnetic interference and corrosion. FBG sensors posses

10、s many advantages when compared with conventional electrical transducers, such as the lightweight, sensitive to strain and temperature variations, low power consumption, resistant to corrosion and fatigue, and immunity

11、 to electromagnetic interference. FBG sensors can also be easily bonded on the surface of the material or embeded in the structure to measure the thermal expansion coefficient, without affecting the structural integrity

12、 of the structure itself. In addition, FBG sensors can be easily multiplexed along a single fiber for distributed sensing in large-area. This paper presents the principle and experimental investigation of measuring the

13、 three-dimensional thermal expansion coefficients of Beryllium by using FBG sensors within the temperature range from -50to +140 . ℃ ℃ 2. PRINCIPLE A fiber-optic Bragg grating (FBG) is a permanent, periodic perturbati

14、on of the refractive index which is laterally exposed into the core of an optical fiber, extending over a limited length of the fiber. The grating is characterized by its period, refractive index amplitude and length.

15、Such a periodic structure acts as a filter for light traveling along the fiber line. It has the property of reflecting light in a predetermined range of wavelength centered around a peak wavelength value. This value, th

16、e Bragg wavelength B λ , is given as follows [4]: 2 B eff n λ = Λ (1) where is the mean effective refractive index in the grating region and eff n Λ is the grating peri

17、od the index modulation. The shift of Bragg wavelength caused by strain and temperature is given as follows : (1 ) ( ) B eB P T λ ε α ζ λ? = ? + + ?(2) Figure 1. The interrogation scheme of FBG sensors 3 Y Y Z54 X2 1 F

18、igure 2. The experiment setup for measuring the three-dimensional expansion coefficient 1: the measured material ; 2:stage; 3:FBG in the direction of x axis;4: FBG in the direction of y axis; 5: FBG in the direction

19、of z axis. Fig. 3 shows the Bragg wavelength response of the reference FBG when the temperature was increased and dropped twice. The slope of the curve in Figure 3 is 0.01071 by linear fitting and the fitting correlatio

20、n coefficient is 0.99907, the standard error is 0.01415. It is obviously that the linearity of the Bragg wavelength as a function of the temperature is good, which make the FBG suitable for temperature sensing. Figure

21、4 shows the Bragg wavelength of the three FBGs bonded on the surfaces of the material in the directions of x, y, z, in the function of temperature. The wavelength shift is caused by both the strain variation induced by

22、 the thermal expansion of the material and the temperature variation. Then considering the temperature compensating, the thermal expansion coefficients in the three direction of x, y, z are different and can be obtaine