POF helical sensor: a simple design approach for vibration measuring based on bend loss coupling

The present study proposed a novel polymer optical fiber sensor design for vibration measuring. The sensor design consists of two fibers; primary and secondary fibers. Where primary fiber leads to optical power loss through bending loss and secondary fiber couples the optical power through phase coupling. The sensor design involves the primary fiber winding on the supportive cylindrical tube to make the sensor helical structure. The winding of the primary fiber makes the eleven bend loops, which are considered as the sensing points. Based on the bend loss theory, each bend loop leads variable amounts of optical power loss. To detect the vibrating motion, the secondary fiber is aligned perpendicularly with the helical structure. Combined primary and secondary fibers generate the proposed vibration sensor. In the experimental setup, the vibration motion continually varies the position of secondary fiber with helical structured fiber to couple variable optical power. The variation in the optical power coupling intensity indicates the vibration motion. The results showed that the proposed sensor design demonstrated its capability to detect the vibration repetitively and different ranges of vibrations effectively. Furthermore, software limitations impose constraints on sampling rates, restricting the proposed sensor's ability to exploit the sensor's high-frequency detection potential fully. Despite this, we have successfully reported the detection of vibrations up to 10 Hz, highlighting the sensor's substantial promise for applications requiring precise vibration monitoring within this frequency range.