A iber optic vibration sensor based on SMF-MMF-SMF structure and a tilted iber Bragg grating

The paper proposes a version of realization for a fiber optic vibration sensor. The sensor possesses a wide range of operation frequencies with such interrogation devices as optical power meters. In comparison to spectral measuring complexes, the sensor imposes lower requirements on operating conditions. The authors investigated a sensing head based on a fiber SMF-MMF-SMF structure and a fiber Bragg grating inscribed in this structure. The external vibration frequency applied to the tested sensor structure is obtained using the Fourier transform of the signal received from the photodetector. The structure designed in this study with a fiber Bragg grating inscribed in it can be used as a sensing head of a fiber optic vibration sensor. It is demonstrated that the sensor based on the developed sensitive structure is able to obtain the external vibration frequency in the range of 20-9 000 Hz with accuracy up to 1 %. The research results are essential for monitoring systems for the state of structural elements of buildings and structures. The implementation of the vibration sensor in the format of a fiber optic device allows overcoming the limitations of piezoelectric sensors, providing high noise immunity and resistance to harsh environmental effects.