String-type based two-dimensional fiber bragg grating vibration sensing principle and structure optimization

Abstract

Vibration is a common phenomenon in the field of engineering, and it typically carries affluent and essential faulty information on health conditions of measured targets. Consequently, it is crucial to ensure safe and stable operations of engineering equipment through the use of effective vibration detection technologies. The increasingly and extensively advanced requirements for vibration detection make it essential to realize real-time multi-dimensional vibration information. To this end, a string-type two-dimensional (2D) fiber Bragg grating (FBG) vibration sensor has been presented through the use of both axial and transverse properties of a tightly suspended optical fiber. This sensor employs a novel mass block structure that possesses a specially designed hole pattern and introduces two stiffening beams through them to enhance the dynamic properties and remove the coupled rotational interference. The sensing principle and the proposed guidelines of cross-interference elimination have been validated by the simulation and experimental results. With the configuration of two stiffening beams, the working bandwidth of the proposed sensor has been enlarged to be respectively 10–150Hz and 10–800Hz along the x and y direction, which were consistent with both theoretical and simulation results. The rotational interference in the x direction has been significantly reduced to 15.3%. However, its complete removal requires a strict fabrication requirement and a bulky sensor size for this design. To further remove the interference and make the sensor compact, an optimized mass structure has been proposed to achieve almost complete removal of the rotational interference in the x direction.