Frequency characteristics of hetero-core fiber optics sensor for mechanical vibration

• A hetero-core fiber optic sensor was applied to a mechanical vibration sensor.
• Natural characteristics of a hetero-core fiber optic sensor are presented.
• A natural frequency of fiber was calculated by FEM fiber beam model with tension.
• The proposed mechanical vibration sensor can easily tune its detectable frequency with the length and tension to the fiber.

In this paper, we present characteristics of a hetero-core fiber optic sensor in mechanical vibration based on rigid supported beam property for vibration monitoring in fault diagnosis of the industrial equipments. A first configuration of the hetero-core fiber optic vibration sensor was rigidly supported at two fixed ends as curved setting without tension to the fiber. In order to tune the range of the detectable frequencies to be higher of the vibration sensor, a second configuration was evaluated, in which the hetero-core fiber optics was linearly-arranged with tension to the fiber. As a result, the both types of the proposed hetero-core fiber optic vibration sensors could pick up the free vibration from an impact force. Analytical natural frequencies were calculated based on an FEM fiber beam model. It was indicated that the natural frequencies from the experimental results of the 1st configuration were appropriate to the FEM results and a typical beam property, and could be tuned by the length between two fixed ends. Additionally, the 2nd configuration of the vibration sensor with tension to the fiber enabled its detectable frequencies to be dramatically higher than without tension.