High-precision bow-shaped fiber Bragg grating micro-displacement sensors

In order to realize small deformation measurements of Numerical Control (NC) machine tool structures and micro-processing platforms, a high-precision optical fiber Bragg grating (FBG) micro-displacement-sensor based on a bow shape was designed. The grating region of the FBG was attached to the upper and lower walls of the bow. Hence, the strain value of the upper and lower walls could be measured while the bow was deformed, allowing displacement measurement and achieving temperature decoupling. Experimental results show that in the displacement range of 1 mm, the sensitivity by fitting a straight line is 2.02 pm/μm, the linearity is 2.92%, the linear correlation coefficient is 0.998 3, the hysteresis error of three groups is 4.08%, and the repeatability error of three groups is 4.08%. A temperature compensation test is presented in addition, showing a wavelength drift of less than 1 pm with a temperature increase of 1℃. Furthermore, a similar half bow structure was derived and compared with the previous bow type in terms of their performance. The comparison shows that the temperature compensation of the bow type is 0.001 5 pm/μm, which is smaller than that of the half bow type, while the latter has a better static calibration linearity of 0.4%. It satisfies the sensor requirements of stability, higher precision, as well as strong electromagnetic interference resistance and temperature insensitivity. © 2018, Science Press. All right reserved.