X-Structure of Torque Adjustable Formed by 3-D Printing With Embedded Optical Fiber Bending for Vibration Sensing

Inexpensive, lightweight, sensitive, compact, easy-to-install, and mass-producible vibration sensors are the future wave. This article validates the use of a 3-D-printed doublet bracket that turns out to be a scissor-like X-structure with scissor-like kinematics when vibrating. The main concept is simple: an intact standard single-mode fiber (SMF) is folded into a droplet-bending shape and embedded in an arch bridge-type assembly connected to an X-shaped structure. When regular vibrations are transmitted to the X-structure, the continuous scissor motion of the X-structure drives the arch bridge-type assembly to regularly extend and shrink, thereby changing the size of the fiber bending, creating variations in the optical loss, and allowing for the measurement of the vibration. In addition, the sensitivity of the vibration measurement can be adjusted by altering the torque by varying the intersection angle of the doublet bracket in the X-structure or the fiber loss by varying the number of turns of fiber bending. In this way, the sensitivity can be adjusted according to the magnitude of the vibration amplitude of the object being measured in various measurement scenarios. For instance, if the vibration amplitude is weak, a high-sensitivity frame will be utilized for the measurement, and vice versa. Furthermore, this 3-D-printed-based X-structure and fiber-bending-based vibration sensor can be integrated with free-space optics (FSOs) for more versatile measurements in various applications. In summary, this scheme showcases an affordable, lightweight, variable-sensitivity, simple, and easily mass-producible fiber-optic vibration sensing technology.